You are here

Spicer, Leonard D.

Overview:

The focus of this laboratory is the study of structure/function relationships in biological macromolecules and their binding interactions. The principal method we use for system characterization is magnetic resonance spectroscopy. One specific area of interest is the structural characterization of functional domains in proteins which regulate the transcription of DNA coding for biosynthetic enzymes. The system under current investigation is the methionine repressor protein metJ, its corepressor S-adenosylmethionine, and the cognate sequence DNA. This protein, which functions as a dimer, exhibits a recently described DNA binding motif involving insertion of two beta strands into the major groove with additional stabilization of the complex arising from helix contacts at the dimer-dimer interface. We are using a full complement of heteronuclear 3D and 4D NMR methods to aid in the assignment of the main chain of the metJ repressor. We have recently reported a thermodynamic analysis of the binding interactions of metJ with its cognate DNA and corepressor SAM. We are now developing methods to measure fast proton exchange rates to complement our planned solution structural characterization.We have just initiated another project in collaboration with scientists at the Pacific Northwest National Laboratory to study macromelecular structures of DNA repair proteins in the nucleotide excision repair pathway. The first components of this critical supramacromolecular assembly we are investigating involve the DNA binding domain of the XPA protein for which we are determining the global fold in solution by NMR. Our program also includes a systematic approach to characterizing the conformational preferences of a number of sequentially related peptides developed by Dr. Barton Haynes' laboratory as candidate vaccines for HIV. The peptides consist of a fusion of two noncontiguous segments of the HIV protein gp120. Our goal is to establish whether structural conformers in solution contribute to peptide immunogenicity. We have finished a careful conformational analysis of the initial four peptides and are now correlating the conformer similarities and differences with immunogenic properties. We have also rationally designed several new peptides based on structural criteria and corresponding structural homology to the heavy fragment of IgA proteins. Initial NMR analysis and immunogenic response to three of the designed mutants indicate the rational design of preferred conformers was successful, but raised some novel questions regarding function of immunogenic peptides. We have also just begun a study of solution conformations of the hypoglycosylated tumor specific epitope repeat unit of human mucin and a promising mutant identified by Dombrowski and Wright. This epitope is common to breast and other adenocarcinomas and regulation of tumor specific lymphoid cells responding to this immunogen may be an important step in tumor control. Another protein under investigation is a functional core packing mutant of thioredoxin. We have fully characterized backbone chain dynamics to assess the impact of this mutation on molecular motions and are currently determining its high resolution tertiary structure. Currently, we are also using this mutant to demonstrate a new approach to global fold determination using a minimum set of long range NMR constraints. Finally, as an essential part of these studies, we are developing and have reported new 3- and 4-dimensional NMR experiments and heteronuclear filters for application to large protein systems and binding complexes.

Finally, the core activities of the NMR Center staff have continued to progress rapidly and enhancements to the state-of-the-art instrumentation have again been incorporated. A new deuteration strategy for assignment and study of large proteins by NMR has been developed and used to characterize one of the largest protein monomer reported to date, human carbonic anhydrase. We have also shown that we can observe the longest range distance constraints to date from NOESY correlations which are important in determining tertiary structure of proteins and we are examining the efficacy of structure determinations based on using these critical but limited constraints.

Positions:

University Distinguished Service Professor of Radiology

Radiology
School of Medicine

Professor of Radiology

Radiology
School of Medicine

Professor of Biochemistry

Biochemistry
School of Medicine

Member of the Duke Cancer Institute

Duke Cancer Institute
School of Medicine

Member of the Duke Human Vaccine Institute

Duke Human Vaccine Institute
School of Medicine

Education:

B.S. 1964

B.S. — University of Michigan at Ann Arbor

Ph.D. 1968

Ph.D. — Yale University

News:

Grants:

Deep Topological Sampling of Protein Structures

Administered By
Computer Science
AwardedBy
National Institutes of Health
Role
Co Investigator
Start Date
September 18, 2017
End Date
July 31, 2021

Structural Biological Development of Fungal-Specific Calcineurin Inhibitors

Administered By
Molecular Genetics and Microbiology
AwardedBy
National Institutes of Health
Role
Co-Principal Investigator
Start Date
August 04, 2014
End Date
July 31, 2018

Structural Biology and Biophysics Training Program

Administered By
Basic Science Departments
AwardedBy
National Institutes of Health
Role
Mentor
Start Date
July 01, 1994
End Date
September 30, 2015

New Console and Cold Probe for the Duke 600 MHz NMR Spectrometer System

Administered By
Radiology
AwardedBy
National Institutes of Health
Role
Co Investigator
Start Date
June 15, 2013
End Date
June 14, 2014

Cross-disciplinary Training in Medical Physics

Administered By
Duke University Medical Physics Graduate Program
AwardedBy
National Institutes of Health
Role
Mentor
Start Date
July 01, 2007
End Date
June 30, 2013

Replacement Equipment Components for an 800 MHz NMR Spectrometer

Administered By
Radiology
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
August 20, 2010
End Date
August 19, 2011

Heteronuclear Multi-dimensional In-Cell NMR Spectroscopy

Administered By
Radiology
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
December 01, 2007
End Date
November 30, 2010

NMR Studies of Proteins and Protein-DNA Binding

Administered By
Radiology
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
July 01, 1989
End Date
June 30, 2002

Acquisition Of An Ultra High Field Spectrometer

Administered By
Radiology
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
September 01, 1999
End Date
August 31, 2000

Cancer Center Core Support Grant

Administered By
Medicine, Medical Oncology
AwardedBy
National Institutes of Health
Role
Co-Principal Investigator
Start Date
September 01, 1976
End Date
December 31, 1998

Comprehensive Cancer Center Core Support Grant

Administered By
Medicine, Medical Oncology
AwardedBy
National Institutes of Health
Role
Co-Principal Investigator
Start Date
September 01, 1976
End Date
December 31, 1998

Comprehensive Cancer Center Core Support Grant

Administered By
Medicine, Medical Oncology
AwardedBy
National Institutes of Health
Role
Co-Principal Investigator
Start Date
September 01, 1976
End Date
December 31, 1998

Peptide Immunogens For Mucosal & Systemic Hiv Vaccines Nat

Administered By
Medicine, Rheumatology and Immunology
AwardedBy
National Institutes of Health
Role
Co-Principal Investigator
Start Date
December 15, 1993
End Date
November 30, 1997

Displaydies Of Protein And Protein-Dna Binding

Administered By
Radiology
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
December 01, 1994
End Date
June 30, 1996

Protein-Dna Binding,(Supplement)

Administered By
Radiology
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
May 04, 1993
End Date
September 01, 1994

Ultra High Field Nmr Spectrometer

Administered By
Radiology
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
April 06, 1990
End Date
April 05, 1993

Acquisition Of An Ultra High Field Nmr Spectrometer

Administered By
Radiology
AwardedBy
National Science Foundation
Role
Principal Investigator
Start Date
May 01, 1990
End Date
October 01, 1992

Analytical Multinuclear 300 Mhz Nmr Spectrometers For Rout

Administered By
Radiology
AwardedBy
National Science Foundation
Role
Principal Investigator
Start Date
August 01, 1986
End Date
January 01, 1988

300 Mhz Analytical Nmr Spectrometer

Administered By
Radiology
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
May 01, 1986
End Date
April 01, 1987
Show More

Publications:

Structures of Pathogenic Fungal FKBP12s Reveal Possible Self-Catalysis Function.

Invasive fungal infections remain difficult to treat and require novel targeting strategies. The 12-kDa FK506-binding protein (FKBP12) is a ubiquitously expressed peptidyl-prolyl isomerase with considerable homology between fungal pathogens and is thus a prime candidate for future targeting efforts to generate a panfungal strategy. Despite decades of research on FKBPs, their substrates and mechanisms of action remain unclear. Here we describe structural, biochemical, and in vivo analyses of FKBP12s from the pathogenic fungi Candida albicans, Candida glabrata, and Aspergillus fumigatus Strikingly, multiple apo A. fumigatus and C. albicans FKBP12 crystal structures revealed a symmetric, intermolecular interaction involving the deep insertion of an active-site loop proline into the active-site pocket of an adjacent subunit. Such interactions have not been observed in previous FKBP structures. This finding indicates the possibility that this is a self-substrate interaction unique to the A. fumigatus and C. albicans fungal proteins that contain this central proline. Structures obtained with the proline in the cis and trans states provide more data in support of self-catalysis. Moreover, cysteine cross-linking experiments captured the interacting dimer, supporting the idea that it forms in solution. Finally, genetic studies exploring the impact of mutations altering the central proline and an adjacent residue provide evidence that any dimeric state formed in vivo, where FKBP12 concentrations are low, is transient. Taken together, these findings suggest a unique mechanism of self-substrate regulation by fungal FKBP12s, lending further novel understanding of this protein for future drug-targeting efforts.FKBP12 is a cis-trans peptidyl-prolyl isomerase that plays key roles in cellular protein homeostasis. FKBP12s also bind the immunosuppressive drug FK506 to inhibit the phosphatase calcineurin (CaN). CaN is required for virulence of A. fumigatus, C. albicans, C. glabrata, and other deadly fungal pathogens, marking FKBP12 and CaN as potential broad-spectrum drug targets. Here we describe structures of fungal FKBP12s. Multiple apo A. fumigatus and C. albicans FKBP12 structures reveal the insertion of a proline, conspicuously conserved in these proteins, into the active sites of adjacent molecules. This suggests that these proteins might serve as their own substrates. Cysteine disulfide trapping experiments provide support for this self-interaction and hence possible intermolecular catalysis by these enzymes.

Authors
Tonthat, NK; Juvvadi, PR; Zhang, H; Lee, SC; Venters, R; Spicer, L; Steinbach, WJ; Heitman, J; Schumacher, MA
MLA Citation
Tonthat, NK, Juvvadi, PR, Zhang, H, Lee, SC, Venters, R, Spicer, L, Steinbach, WJ, Heitman, J, and Schumacher, MA. "Structures of Pathogenic Fungal FKBP12s Reveal Possible Self-Catalysis Function." mBio 7.2 (April 26, 2016): e00492-e00416.
PMID
27118592
Source
epmc
Published In
mBio
Volume
7
Issue
2
Publish Date
2016
Start Page
e00492
End Page
e00416
DOI
10.1128/mbio.00492-16

Structure of an HIV-1-neutralizing antibody target, the lipid-bound gp41 envelope membrane proximal region trimer.

The membrane proximal external region (MPER) of HIV-1 glycoprotein (gp) 41 is involved in viral-host cell membrane fusion. It contains short amino acid sequences that are binding sites for the HIV-1 broadly neutralizing antibodies 2F5, 4E10, and 10E8, making these binding sites important targets for HIV-1 vaccine development. We report a high-resolution structure of a designed MPER trimer assembled on a detergent micelle. The NMR solution structure of this trimeric domain, designated gp41-M-MAT, shows that the three MPER peptides each adopt symmetric α-helical conformations exposing the amino acid side chains of the antibody binding sites. The helices are closely associated at their N termini, bend between the 2F5 and 4E10 epitopes, and gradually separate toward the C termini, where they associate with the membrane. The mAbs 2F5 and 4E10 bind gp41-M-MAT with nanomolar affinities, consistent with the substantial exposure of their respective epitopes in the trimer structure. The traditional structure determination of gp41-M-MAT using the Xplor-NIH protocol was validated by independently determining the structure using the DISCO sparse-data protocol, which exploits geometric arrangement algorithms that guarantee to compute all structures and assignments that satisfy the data.

Authors
Reardon, PN; Sage, H; Dennison, SM; Martin, JW; Donald, BR; Alam, SM; Haynes, BF; Spicer, LD
MLA Citation
Reardon, PN, Sage, H, Dennison, SM, Martin, JW, Donald, BR, Alam, SM, Haynes, BF, and Spicer, LD. "Structure of an HIV-1-neutralizing antibody target, the lipid-bound gp41 envelope membrane proximal region trimer." Proceedings of the National Academy of Sciences of the United States of America 111.4 (January 13, 2014): 1391-1396.
PMID
24474763
Source
epmc
Published In
Proceedings of the National Academy of Sciences of USA
Volume
111
Issue
4
Publish Date
2014
Start Page
1391
End Page
1396
DOI
10.1073/pnas.1309842111

Identification of autoantigens recognized by the 2F5 and 4E10 broadly neutralizing HIV-1 antibodies.

Many human monoclonal antibodies that neutralize multiple clades of HIV-1 are polyreactive and bind avidly to mammalian autoantigens. Indeed, the generation of neutralizing antibodies to the 2F5 and 4E10 epitopes of HIV-1 gp41 in man may be proscribed by immune tolerance because mice expressing the V(H) and V(L) regions of 2F5 have a block in B cell development that is characteristic of central tolerance. This developmental blockade implies the presence of tolerizing autoantigens that are mimicked by the membrane-proximal external region of HIV-1 gp41. We identify human kynureninase (KYNU) and splicing factor 3b subunit 3 (SF3B3) as the primary conserved, vertebrate self-antigens recognized by the 2F5 and 4E10 antibodies, respectively. 2F5 binds the H4 domain of KYNU which contains the complete 2F5 linear epitope (ELDKWA). 4E10 recognizes an epitope of SF3B3 that is strongly dependent on hydrophobic interactions. Opossums carry a rare KYNU H4 domain that abolishes 2F5 binding, but they retain the SF3B3 4E10 epitope. Immunization of opossums with HIV-1 gp140 induced extraordinary titers of serum antibody to the 2F5 ELDKWA epitope but little or nothing to the 4E10 determinant. Identification of structural motifs shared by vertebrates and HIV-1 provides direct evidence that immunological tolerance can impair humoral responses to HIV-1.

Authors
Yang, G; Holl, TM; Liu, Y; Li, Y; Lu, X; Nicely, NI; Kepler, TB; Alam, SM; Liao, H-X; Cain, DW; Spicer, L; VandeBerg, JL; Haynes, BF; Kelsoe, G
MLA Citation
Yang, G, Holl, TM, Liu, Y, Li, Y, Lu, X, Nicely, NI, Kepler, TB, Alam, SM, Liao, H-X, Cain, DW, Spicer, L, VandeBerg, JL, Haynes, BF, and Kelsoe, G. "Identification of autoantigens recognized by the 2F5 and 4E10 broadly neutralizing HIV-1 antibodies." The Journal of experimental medicine 210.2 (February 2013): 241-256.
Website
http://hdl.handle.net/10161/10900
PMID
23359068
Source
epmc
Published In
The Journal of Experimental Medicine
Volume
210
Issue
2
Publish Date
2013
Start Page
241
End Page
256
DOI
10.1084/jem.20121977

In-cell NMR spectroscopy in Escherichia coli.

A living cell is a complex system that contains many biological macromolecules and small molecules necessary for survival, in a relatively small volume. It is within this crowded and complex cellular environment that proteins function making in-cell studies of protein structure and binding interactions an exciting and important area of study. Nuclear magnetic resonance (NMR) spectroscopy is a particularly attractive method for in-cell studies of proteins since it provides atomic-level data noninvasively in solution. In addition, NMR has recently undergone significant advances in instrumentation to increase sensitivity and in methods development to reduce data acquisition times for multidimensional experiments. Thus, NMR spectroscopy lends itself to studying proteins within a living cell, and recently "in-cell NMR" studies have been reported from several laboratories. To date, this technique has been successfully applied in Escherichia coli (E. coli), Xenopus laevis (X. laevis) oocytes, and HeLa host cells. Demonstrated applications include protein assignment as well as de novo 3D protein structure determination. The most common use, however, is to probe binding interactions and structural modifications directly from proton nitrogen correlation spectra. E. coli is the most extensively used cell type thus far and this chapter is largely confined to reviewing recent literature and describing methods and detailed protocols for in-cell NMR studies in this bacterial cell.

Authors
Robinson, KE; Reardon, PN; Spicer, LD
MLA Citation
Robinson, KE, Reardon, PN, and Spicer, LD. "In-cell NMR spectroscopy in Escherichia coli." Methods Mol Biol 831 (2012): 261-277. (Review)
PMID
22167679
Source
pubmed
Published In
Methods in molecular biology (Clifton, N.J.)
Volume
831
Publish Date
2012
Start Page
261
End Page
277
DOI
10.1007/978-1-61779-480-3_15

The MetJ regulon in gammaproteobacteria determined by comparative genomics methods.

BACKGROUND: Whole-genome sequencing of bacteria has proceeded at an exponential pace but annotation validation has lagged behind. For instance, the MetJ regulon, which controls methionine biosynthesis and transport, has been studied almost exclusively in E. coli and Salmonella, but homologs of MetJ exist in a variety of other species. These include some that are pathogenic (e.g. Yersinia) and some that are important for environmental remediation (e.g. Shewanella) but many of which have not been extensively characterized in the literature. RESULTS: We have determined the likely composition of the MetJ regulon in all species which have MetJ homologs using bioinformatics techniques. We show that the core genes known from E. coli are consistently regulated in other species, and we identify previously unknown members of the regulon. These include the cobalamin transporter, btuB; all the genes involved in the methionine salvage pathway; as well as several enzymes and transporters of unknown specificity. CONCLUSIONS: The MetJ regulon is present and functional in five orders of gammaproteobacteria: Enterobacteriales, Pasteurellales, Vibrionales, Aeromonadales and Alteromonadales. New regulatory activity for MetJ was identified in the genomic data and verified experimentally. This strategy should be applicable for the elucidation of regulatory pathways in other systems by using the extensive sequencing data currently being generated.

Authors
Augustus, AM; Spicer, LD
MLA Citation
Augustus, AM, and Spicer, LD. "The MetJ regulon in gammaproteobacteria determined by comparative genomics methods. (Published online)" BMC Genomics 12 (November 14, 2011): 558-.
PMID
22082356
Source
pubmed
Published In
BMC Genomics
Volume
12
Publish Date
2011
Start Page
558
DOI
10.1186/1471-2164-12-558

Crystal structure of a non-neutralizing antibody to the HIV-1 gp41 membrane-proximal external region.

The monoclonal antibody 13H11 shares part of its epitope in the HIV-1 gp41 membrane-proximal external region (MPER) with the rare, broadly neutralizing human antibody 2F5. Although 13H11 partially cross-blocked 2F5 binding, 13H11 is non-neutralizing and does not block 2F5 neutralization. We show that unlike 2F5, 13H11 binds to a well-defined helical MPER structure that is consistent with the structure of gp41 in a post-fusion six-helix bundle conformation.

Authors
Nicely, NI; Dennison, SM; Spicer, L; Scearce, RM; Kelsoe, G; Ueda, Y; Chen, H; Liao, H-X; Alam, SM; Haynes, BF
MLA Citation
Nicely, NI, Dennison, SM, Spicer, L, Scearce, RM, Kelsoe, G, Ueda, Y, Chen, H, Liao, H-X, Alam, SM, and Haynes, BF. "Crystal structure of a non-neutralizing antibody to the HIV-1 gp41 membrane-proximal external region." Nat Struct Mol Biol 17.12 (December 2010): 1492-1494.
PMID
21076400
Source
pubmed
Published In
Nature Structural & Molecular Biology
Volume
17
Issue
12
Publish Date
2010
Start Page
1492
End Page
1494
DOI
10.1038/nsmb.1944

Binding of MetJ repressor to specific and nonspecific DNA and effect of S-adenosylmethionine on these interactions.

We have used analytical ultracentrifugation to characterize the binding of the methionine repressor protein, MetJ, to synthetic oligonucleotides containing zero to five specific recognition sites, called metboxes. For all lengths of DNA studied, MetJ binds more tightly to repeats of the consensus sequence than to naturally occurring metboxes, which exhibit a variable number of deviations from the consensus. Strong cooperative binding occurs only in the presence of two or more tandem metboxes, which facilitate protein-protein contacts between adjacent MetJ dimers, but weak affinity is detected even with DNA containing zero or one metbox. The affinity of MetJ for all of the DNA sequences studied is enhanced by the addition of SAM, the known cofactor for MetJ in the cell. This effect extends to oligos containing zero or one metbox, both of which bind two MetJ dimers. In the presence of a large excess concentration of metbox DNA, the effect of cooperativity is to favor populations of DNA oligos bound by two or more MetJ dimers rather than a stochastic redistribution of the repressor onto all available metboxes. These results illustrate the dynamic range of binding affinity and repressor assembly that MetJ can exhibit with DNA and the effect of the corepressor SAM on binding to both specific and nonspecific DNA.

Authors
Augustus, AM; Sage, H; Spicer, LD
MLA Citation
Augustus, AM, Sage, H, and Spicer, LD. "Binding of MetJ repressor to specific and nonspecific DNA and effect of S-adenosylmethionine on these interactions." Biochemistry 49.15 (April 20, 2010): 3289-3295.
Website
http://hdl.handle.net/10161/4018
PMID
20196619
Source
pubmed
Published In
Biochemistry
Volume
49
Issue
15
Publish Date
2010
Start Page
3289
End Page
3295
DOI
10.1021/bi902011f

MetJ repressor interactions with DNA probed by in-cell NMR.

Atomic level characterization of proteins and other macromolecules in the living cell is challenging. Recent advances in NMR instrumentation and methods, however, have enabled in-cell studies with prospects for multidimensional spectral characterization of individual macromolecular components. We present NMR data on the in-cell behavior of the MetJ repressor from Escherichia coli, a protein that regulates the expression of genes involved in methionine biosynthesis. NMR studies of whole cells along with corresponding studies in cell lysates and in vitro preparations of the pure protein give clear evidence for extensive nonspecific interactions with genomic DNA. These interactions can provide an efficient mechanism for searching out target sequences by reducing the dependence on 3-dimensional diffusion through the crowded cellular environment. DNA provides the track for MetJ to negotiate the obstacles inherent in cells and facilitates locating and binding specific repression sites, allowing for timely control of methionine biosynthesis.

Authors
Augustus, AM; Reardon, PN; Spicer, LD
MLA Citation
Augustus, AM, Reardon, PN, and Spicer, LD. "MetJ repressor interactions with DNA probed by in-cell NMR." Proc Natl Acad Sci U S A 106.13 (March 31, 2009): 5065-5069.
PMID
19289840
Source
pubmed
Published In
Proceedings of the National Academy of Sciences of USA
Volume
106
Issue
13
Publish Date
2009
Start Page
5065
End Page
5069
DOI
10.1073/pnas.0811130106

Structural basis for the differential regulation of DNA by the methionine repressor MetJ.

The Met regulon in Escherichia coli encodes several proteins responsible for the biosynthesis of methionine. Regulation of the expression of most of these proteins is governed by the methionine repressor protein MetJ and its co-repressor, the methionine derivative S-adenosylmethionine. Genes controlled by MetJ contain from two to five sequential copies of a homologous 8-bp sequence called the metbox. A crystal structure for one of the complexes, the repressor tetramer bound to two metboxes, has been reported (Somers, W. S., and S. E. Phillips (1992) Nature 359, 387-393), but little structural work on the larger assemblies has been done presumably because of the difficulties in crystallization and the variability in the number and sequences of metboxes for the various genes. Small angle neutron scattering was used to study complexes of MetJ and S-adenosylmethionine with double-stranded DNA containing two, three, and five metboxes. Our results demonstrate that the crystal structure of the two-metbox complex is not the native solution conformation of the complex. Instead, the system adopts a less compact conformation in which there is decreased interaction between the adjacent MetJ dimers. Models built of the higher order complexes from the scattering data show that the three-metbox complex is organized much like the two-metbox complex. However, the five-metbox complex differs significantly from the smaller complexes, providing much closer packing of the adjacent MetJ dimers and allowing additional contacts not available in the crystal structure. The results suggest that there is a structural basis for the differences observed in the regulatory effectiveness of MetJ for the various genes of the Met regulon.

Authors
Augustus, AM; Reardon, PN; Heller, WT; Spicer, LD
MLA Citation
Augustus, AM, Reardon, PN, Heller, WT, and Spicer, LD. "Structural basis for the differential regulation of DNA by the methionine repressor MetJ." J Biol Chem 281.45 (November 10, 2006): 34269-34276.
PMID
16963446
Source
pubmed
Published In
The Journal of biological chemistry
Volume
281
Issue
45
Publish Date
2006
Start Page
34269
End Page
34276
DOI
10.1074/jbc.M605763200

Multidimensional NMR spectroscopy for protein characterization and assignment inside cells.

High-field, heteronuclear NMR spectroscopy of biological macromolecules in native cellular environments is limited by the low concentrations present and the long data acquisition times needed for the experiments. Successful 1D and 2D heteronuclear NMR data have been reported, but the 3D experiments conventionally used for protein assignment and detailed characterization are generally too long to maintain cell viability. Here we describe the successful in vivo implementation of a suite of fast 3D NMR experiments which we have used to generate the complete backbone assignment of resonances in the recombinant polypeptide GB-1 within Escherichia coli cells. The data were acquired at 600 MHz with a cold probe using the projection reconstruction experiments, (3,2)HNCA, (3,2)HNCO, and (3,2)HA(CA)NH.

Authors
Reardon, PN; Spicer, LD
MLA Citation
Reardon, PN, and Spicer, LD. "Multidimensional NMR spectroscopy for protein characterization and assignment inside cells." J Am Chem Soc 127.31 (August 10, 2005): 10848-10849.
PMID
16076188
Source
pubmed
Published In
Journal of the American Chemical Society
Volume
127
Issue
31
Publish Date
2005
Start Page
10848
End Page
10849
DOI
10.1021/ja053145k

DNA-XPA interactions: a (31)P NMR and molecular modeling study of dCCAATAACC association with the minimal DNA-binding domain (M98-F219) of the nucleotide excision repair protein XPA.

Recent NMR-based, chemical shift mapping experiments with the minimal DNA-binding domain of XPA (XPA-MBD: M98-F219) suggest that a basic cleft located in the loop-rich subdomain plays a role in DNA-binding. Here, XPA-DNA interactions are further characterized by NMR spectroscopy from the vantage point of the DNA using a single-stranded DNA nonamer, dCCAATAACC (d9). Up to 2.5 molar equivalents of XPA-MBD was titrated into a solution of d9. A subset of (31)P resonances of d9 were observed to broaden and/or shift providing direct evidence that XPA-MBD binds d9 by a mechanism that perturbs the phosphodiester backbone of d9. The interior five residues of d9 broadened and/or shifted before (31)P resonances of phosphate groups at the termini, suggesting that when d9 is bound to XPA-MBD the internal residues assume a correlation time that is characteristic of the molecular weight of the complex while the residues at the termini undergo a fraying motion away from the surface of the protein on a timescale such that the line widths are more characteristic of the molecular weight of ssDNA. A molecular model of the XPA-MBD complex with d9 was calculated based on the (15)N (XPA-MBD) and (31)P (d9) chemical shift mapping studies and on the assumption that electrostatic interactions drive the complex formation. The model shows that a nine residue DNA oligomer fully covers the DNA-binding surface of XPA and that there may be an energetic advantage to binding DNA in the 3'-->5' direction rather than in the 5'-->3' direction (relative to XPA-MBD alpha-helix-3).

Authors
Buchko, GW; Tung, CS; McAteer, K; Isern, NG; Spicer, LD; Kennedy, MA
MLA Citation
Buchko, GW, Tung, CS, McAteer, K, Isern, NG, Spicer, LD, and Kennedy, MA. "DNA-XPA interactions: a (31)P NMR and molecular modeling study of dCCAATAACC association with the minimal DNA-binding domain (M98-F219) of the nucleotide excision repair protein XPA." Nucleic Acids Res 29.12 (June 15, 2001): 2635-2643.
PMID
11410673
Source
pubmed
Published In
Nucleic Acids Research
Volume
29
Issue
12
Publish Date
2001
Start Page
2635
End Page
2643

Human nucleotide excision repair protein XPA: NMR spectroscopic studies of an XPA fragment containing the ERCC1-binding region and the minimal DNA-binding domain (M59-F219).

XPA is a central protein component of nucleotide excision repair (NER), a ubiquitous, multi-component cellular pathway responsible for the removal and repair of many structurally distinct DNA lesions from the eukaryotic genome. The solution structure of the minimal DNA-binding domain of XPA (XPA-MBD: M98-F219) has recently been determined and chemical shift mapping experiments with 15N-labeled XPA-MBD show that XPA binds DNA along a basic surface located in the C-terminal loop-rich subdomain. Here, XPA-DNA interactions are further characterized using an XPA fragment containing the minimal DNA-binding domain plus the ERCC1-binding region (XPA-EM: M59-F219). The 15N/1H HSQC spectrum of XPA-EM closely maps onto the 15N/1H HSQC spectrum of XPA-MBD, suggesting the DNA-binding domain is intact in the larger XPA fragment. Such a conclusion is corroborated by chemical shift mapping experiments of XPA-EM with a single strand DNA oligomer, dCCAATAACC (d9), that show the same set of 15N/1H HSQC cross peaks are effected by the addition of DNA. However, relative to DNA-free XPA-MBD, the 15N/1H HSQC cross peaks of many of the basic residues in the loop-rich subdomain of DNA-free XPA-EM are less intense, or gone altogether, suggesting the acidic ERRC1-binding region of XPA-EM may associate transiently with the basic DNA-binding surface. While the DNA-binding domain in XPA-EM is structured and functional, 15N-edited NOESY spectra of XPA-EM indicate that the acidic ERRC1-binding region is unstructured. If the structural features observed for XPA-EM persist in XPA, transient intramolecular association of the ERCC1-binding domain with the DNA-binding region may play a role in the sequential assembly of the NER components.

Authors
Buchko, GW; Isern, NG; Spicer, LD; Kennedy, MA
MLA Citation
Buchko, GW, Isern, NG, Spicer, LD, and Kennedy, MA. "Human nucleotide excision repair protein XPA: NMR spectroscopic studies of an XPA fragment containing the ERCC1-binding region and the minimal DNA-binding domain (M59-F219)." Mutat Res 486.1 (June 5, 2001): 1-10.
PMID
11356331
Source
pubmed
Published In
Mutation Research - Fundamental and Molecular Mechanisms of Mutagenesis
Volume
486
Issue
1
Publish Date
2001
Start Page
1
End Page
10

Interactions of human nucleotide excision repair protein XPA with DNA and RPA70 Delta C327: chemical shift mapping and 15N NMR relaxation studies.

Human XPA is an essential component in the multienzyme nucleotide excision repair (NER) pathway. The solution structure of the minimal DNA binding domain of XPA (XPA-MBD: M98-F219) was recently determined [Buchko et al. (1998) Nucleic Acids Res. 26, 2779-2788, Ikegami et al. (1998) Nat. Struct. Biol. 5, 701-706] and shown to consist of a compact zinc-binding core and a loop-rich C-terminal subdomain connected by a linker sequence. Here, the solution structure of XPA-MBD was further refined using an entirely new class of restraints based on pseudocontact shifts measured in cobalt-substituted XPA-MBD. Using this structure, the surface of XPA-MBD which interacts with DNA and a fragment of the largest subunit of replication protein A (RPA70 Delta C327: M1-Y326) was determined using chemical shift mapping. DNA binding in XPA-MBD was highly localized in the loop-rich subdomain for DNA with or without a lesion [dihydrothymidine (dhT) or 6-4-thymidine-cytidine (64TC)], or with DNA in single- or double-stranded form, indicating that the character of the lesion itself is not the driving force for XPA binding DNA. RPA70 Delta C327 was found to contact regions in both the zinc-binding and loop-rich subdomains. Some overlap of the DNA and RPA70 Delta C327 binding regions was observed in the loop-rich subdomain, indicating a possible cooperative DNA-binding mode between XPA and RPA70 Delta C327. To complement the chemical shift mapping data, the backbone dynamics of free XPA-MBD and XPA-MBD bound to DNA oligomers containing dhT or 64TC lesions were investigated using 15N NMR relaxation data. The dynamic analyses for the XPA-MBD complexes with DNA revealed localized increases and decreases in S2 and an increase in the global correlation time. Regions of XPA-MBD with the largest increases in S2 overlapped regions having the largest chemical shifts changes upon binding DNA, indicating that the loop-rich subdomain becomes more rigid upon binding DNA. Interestingly, S2 decreased for some residues in the zinc-binding core upon DNA association, indicating a possible concerted structural rearrangement on binding DNA.

Authors
Buchko, GW; Daughdrill, GW; de Lorimier, R; Rao B, K; Isern, NG; Lingbeck, JM; Taylor, JS; Wold, MS; Gochin, M; Spicer, LD; Lowry, DF; Kennedy, MA
MLA Citation
Buchko, GW, Daughdrill, GW, de Lorimier, R, Rao B, K, Isern, NG, Lingbeck, JM, Taylor, JS, Wold, MS, Gochin, M, Spicer, LD, Lowry, DF, and Kennedy, MA. "Interactions of human nucleotide excision repair protein XPA with DNA and RPA70 Delta C327: chemical shift mapping and 15N NMR relaxation studies." Biochemistry 38.46 (November 16, 1999): 15116-15128.
PMID
10563794
Source
pubmed
Published In
Biochemistry
Volume
38
Issue
46
Publish Date
1999
Start Page
15116
End Page
15128

Nuclear magnetic resonance analysis of solution conformations in C4-V3 hybrid peptides derived from human immunodeficiency virus (HIV) type 1 gp120: relation to specificity of peptide-induced anti-HIV neutralizing antibodies.

Immunogenic peptides containing epitopes of the gp120 C4 and V3 regions from human immunodeficiency virus strains MN and EV91 have been studied by nuclear magnetic resonance and molecular modeling and used as immunogens in rhesus monkeys. The results, combined with those for other peptides, suggest a correlation between solution conformation and immunologic cross-reactivity.

Authors
Vu, HM; Myers, D; de Lorimier, R; Matthews, TJ; Moody, MA; Heinly, C; Torres, JV; Haynes, BF; Spicer, L
MLA Citation
Vu, HM, Myers, D, de Lorimier, R, Matthews, TJ, Moody, MA, Heinly, C, Torres, JV, Haynes, BF, and Spicer, L. "Nuclear magnetic resonance analysis of solution conformations in C4-V3 hybrid peptides derived from human immunodeficiency virus (HIV) type 1 gp120: relation to specificity of peptide-induced anti-HIV neutralizing antibodies." J Virol 73.1 (January 1999): 746-750.
PMID
9847381
Source
pubmed
Published In
Journal of virology
Volume
73
Issue
1
Publish Date
1999
Start Page
746
End Page
750

Strategies for NMR assignment and global fold determinations using perdeuterated proteins

Authors
Venters, RA; Vu, HM; Lorimier, RMD; Spicer, LD
MLA Citation
Venters, RA, Vu, HM, Lorimier, RMD, and Spicer, LD. "Strategies for NMR assignment and global fold determinations using perdeuterated proteins." Techniques in Protein Chemistry 8.C (1997): 605-615.
Source
scival
Published In
Techniques in Protein Chemistry
Volume
8
Issue
C
Publish Date
1997
Start Page
605
End Page
615
DOI
10.1016/S1080-8914(97)80060-9

Nmr investigation of a microtubule binding region peptide from human tau (τ) protein

Solution NMR studies of τD1, an 18-residue microtubule binding peptide from domain 1 of human tau protein, are reported. Using 2D 1H NMR (TOCSY, NOESY and ROESY) at 5 and 37°C, we assigned the resonances of almost all protons of τD1 at pH 4.2,5.8 and 7.3. While overall the peptide is highly disordered, several medium range NOE's give evidence for conformational preferences involving a bend at the T8-Q14 segment of the peptide.

Authors
Serrano, VD; Ribeiro, AA; Strittmatter, WJ; Spicer, LD
MLA Citation
Serrano, VD, Ribeiro, AA, Strittmatter, WJ, and Spicer, LD. "Nmr investigation of a microtubule binding region peptide from human tau (τ) protein." Protein and Peptide Letters 4.3 (1997): 165-172.
Source
scival
Published In
Protein and Peptide Letters
Volume
4
Issue
3
Publish Date
1997
Start Page
165
End Page
172

Characterizing the use of perdeuteration in NMR studies of large proteins: 13C, 15N and 1H assignments of human carbonic anhydrase II.

Perdeuteration of all non-exchangeable proton sites can significantly increase the size of proteins and protein complexes for which NMR resonance assignments and structural studies are possible. Backbone 1H, 15N, 13CO, 13C alpha and 13C beta chemical shifts and aliphatic side-chain 13C and 1H(N)/15N chemical shifts for human carbonic anhydrase II (HCA II), a 259 residue 29 kDa metalloenzyme, have been determined using a strategy based on 2D, 3D and 4D heteronuclear NMR experiments, and on perdeuterated 13C/15N-labeled protein. To date, HCA II is one of the largest monomeric proteins studied in detail by high-resolution NMR. Of the backbone resonances, 85% have been assigned using fully protonated 15N and 3C/15N-labeled protein in conjunction with established procedures based on now standard 2D and 3D NMR experiments. HCA II has been perdeuterated both to complete the backbone resonance assignment and to assign the aliphatic side-chain 13C and 1H(N)/15N resonances. The incorporation of 2H into HCA II dramatically decreases the rate of 13C and 1H(N)T2 relaxation. This, in turn, increases the sensitivity of several key 1H/13C/15N triple-resonance correlation experiments. Many otherwise marginal heteronuclear 3D and 4D correlation experiments, which are important to the assignment strategy detailed herein, can now be executed successfully on HCA II. Further analysis suggests that, from the perspective of sensitivity, perdeuteration should allow other proteins with rotational correlation times significantly longer than HCA II (tau c = 11.4 ns) to be studied successfully with these experiments. Two different protocols have been used to characterize the secondary structure of HCA II from backbone chemical-shift data. Secondary structural elements determined in this manner compare favorably with those elements determined from a consensus analysis of the HCA II crystal structure. Finally, having outlined a general strategy for assigning backbone and side-chain resonances in a perdeuterated large protein, we propose a strategy whereby this information can be used to glean more detailed structural information from the partially or fully protonated protein equivalent.

Authors
Venters, RA; Farmer, BT; Fierke, CA; Spicer, LD
MLA Citation
Venters, RA, Farmer, BT, Fierke, CA, and Spicer, LD. "Characterizing the use of perdeuteration in NMR studies of large proteins: 13C, 15N and 1H assignments of human carbonic anhydrase II." J Mol Biol 264.5 (December 20, 1996): 1101-1116.
PMID
9000633
Source
pubmed
Published In
Journal of Molecular Biology
Volume
264
Issue
5
Publish Date
1996
Start Page
1101
End Page
1116

NMR studies of structure, hydrogen exchange, and main-chain dynamics in a disrupted-core mutant of thioredoxin.

Core-packing mutants of proteins often approach molten globule states, and hence may have attributes of folding intermediates. We have studied a core-packing mutant of thioredoxin, L78K, in which a leucine residue is substituted by lysine, using 15N heteronuclear two- and three-dimensional NMR. Chemical shift differences between the mutant and wild-type main-chain resonances reveal that structural changes caused by the mutation are localized within 12 A of the altered side chain. The majority of resonances are unchanged, as are many 1H-1H NOEs indicative of the main-chain fold, suggesting that the structure of L78K is largely similar to wild type. Hydrogen exchange studies reveal that residues comprising the central beta-sheet of both mutant and wild-type proteins constitute a local unfolding unit, but with the unfolding/folding equilibrium approximately 12 times larger in L78K. The dynamics of main-chain NH bonds in L78K were studied by 15N spin relaxation and compared with a previous study of wild type. Order parameters for angular motion of NH bonds in the mutant are on average lower than in wild type, suggesting greater spatial freedom on a rapid time scale, but may also be related to different rotational correlation times in the two proteins. There is also evidence of greater conformational exchange in the mutant. Differences between mutant and wild type in hydrogen exchange and main-chain dynamics are not confined to the vicinity of the mutation. We infer that mispacking of the protein core in one location affects local dynamics and stability throughout.

Authors
De Lorimier, R; Hellinga, HW; Spicer, LD
MLA Citation
De Lorimier, R, Hellinga, HW, and Spicer, LD. "NMR studies of structure, hydrogen exchange, and main-chain dynamics in a disrupted-core mutant of thioredoxin." Protein Sci 5.12 (December 1996): 2552-2565.
PMID
8976564
Source
pubmed
Published In
Protein Science
Volume
5
Issue
12
Publish Date
1996
Start Page
2552
End Page
2565
DOI
10.1002/pro.5560051218

Conformational preferences of a chimeric peptide HIV-1 immunogen from the C4-V3 domains of gp120 envelope protein of HIV-1 CAN0A based on solution NMR: comparison to a related immunogenic peptide from HIV-1 RF.

A critical problem to overcome on HIV vaccine design is the variability among HIV strains. One strategy to solve this problem is the construction of multicomponent immunogens reflective of common HIV motifs. Currently, it is not known if these motifs should be based primarily on amino acid sequence or higher-order structure of the viral proteins of a combination of the two. In this paper, we report NMR-derived solution conformations for a sympathetic peptide taken from the C4 and V3 domains of HIV-1 CAN0A gp120 envelope protein. This peptide, designated T1-SP10CAN0(A), is compared to a recently reported C4-V3 peptide. T1-SP10RF(A) from the HIV-1 RF strain [de Lorimier et al. (1994) Biochemistry 33, 2055-2062], in terms of conformational features and immune responses in mice [Haynes et al. (1995) AIDS Res. Hum. Retroviruses 11, 211-221]. The T1 segment of 16 amino acids from the gp120 C4 domain is identical in both peptides and exhibits nascent helical character. The SP10 region, taken from the gp120 V3 loop, differs from that of T1-SP10RF(A) in both sequence and conformations. A reverse turn is observed at the conserved GPGX sequence. The rest of the Sp10 domain is extended with the exception of the last three residues which show evidence for a helical arrangement. Modeling of the turn region of the T1-SP10CAN0(A) peptide shows exposure of a continuous apolar stretch of side chains similar to that reported in the crystal structure of a V3 peptide from HIV-1 MN complexed with a monoclonal antibody [Rini et al. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 6325-6329]. this hydrophobic patch is interrupted by a charged Lys residue in the T1-SP10RF(A) peptide. This observation suggests that the HIV-1 CAN0A and HIV-1 RF C4-V3 peptides can induce widely different anti-HIV antibodies. consistent with immunogenic results.

Authors
Vu, HM; de Lorimier, R; Moody, MA; Haynes, BF; Spicer, LD
MLA Citation
Vu, HM, de Lorimier, R, Moody, MA, Haynes, BF, and Spicer, LD. "Conformational preferences of a chimeric peptide HIV-1 immunogen from the C4-V3 domains of gp120 envelope protein of HIV-1 CAN0A based on solution NMR: comparison to a related immunogenic peptide from HIV-1 RF." Biochemistry 35.16 (April 23, 1996): 5158-5165.
PMID
8611499
Source
pubmed
Published In
Biochemistry
Volume
35
Issue
16
Publish Date
1996
Start Page
5158
End Page
5165
DOI
10.1021/bi952665x

Improved excitation pulse bandwidths using shaped pulses, with application to heteronuclear half filters in macromolecular NMR.

The advantageous use of sinc-shaped pulses in heteronuclear half filters is explored for studying biological macromolecules. The typical square, or hard, pulse used in half-filter pulse sequences for heteronuclear excitation results in suboptimal suppression of unwanted resonances due to incomplete inversion of spins. The novel use of short-duration shaped pulses applied at high power achieves more uniform excitation profiles over the extended frequency ranges often needed for heteronuclear filtering. This approach is used in the development of a double-tuned omega 1, omega 2-double-half-filtered, double-quantum-filtered COSY experiment. The efficiency of this experiment incorporating sinc pulses compares favorably with that obtained with square pulses in a mixture of 13C-labeled and unlabeled amino acids. Sinc-pulse-filtered spectra of the 24 kDa methionine repressor protein dimer MetJ, uniformly 13C-labeled expect at two unlabeled methionine residues, were also obtained to demonstrate the utility of this approach in biomacromolecular studies.

Authors
Hyre, DE; Spicer, LD
MLA Citation
Hyre, DE, and Spicer, LD. "Improved excitation pulse bandwidths using shaped pulses, with application to heteronuclear half filters in macromolecular NMR." J Magn Reson B 108.1 (July 1995): 12-21.
PMID
7627432
Source
pubmed
Published In
Journal of Magnetic Resonance, Series B
Volume
108
Issue
1
Publish Date
1995
Start Page
12
End Page
21

High-level 2H/13C/15N labeling of proteins for NMR studies.

The protein human carbonic anhydrase II (HCA II) has been isotopically labeled with 2H, 13C and 15N for high-resolution NMR assignment studies and pulse sequence development. To increase the sensitivity of several key 1H/13C/15N triple-resonance correlation experiments, 2H has been incorporated into HCA II in order to decrease the rates of 13C and 1HN T2 relaxation. NMR quantities of protein with essentially complete aliphatic 2H incorporation have been obtained by growth of E. coli in defined media containing D2O, [1,2-13C2, 99%] sodium acetate, and [15N, 99%] ammonium chloride. Complete aliphatic deuterium enrichment is optimal for 13C and 15N backbone NMR assignment studies, since the 13C and 1HN T2 relaxation times and, therefore, sensitivity are maximized. In addition, complete aliphatic deuteration increases both resolution and sensitivity by eliminating the differential 2H isotopic shift observed for partially deuterated CHnDm moieties.

Authors
Venters, RA; Huang, CC; Farmer, BT; Trolard, R; Spicer, LD; Fierke, CA
MLA Citation
Venters, RA, Huang, CC, Farmer, BT, Trolard, R, Spicer, LD, and Fierke, CA. "High-level 2H/13C/15N labeling of proteins for NMR studies." J Biomol NMR 5.4 (June 1995): 339-344.
PMID
7647552
Source
pubmed
Published In
Journal of Biomolecular NMR
Volume
5
Issue
4
Publish Date
1995
Start Page
339
End Page
344

Thermodynamic evaluation of binding interactions in the methionine repressor system of Escherichia coli using isothermal titration calorimetry.

The binding interactions of the methionine repressor protein, MetJ, from Escherichia coli with its cognate, metbox DNA sequence and corepressor S-adenosylmethionine were examined using calorimetric methods. A detailed thermodynamic characterization of this system which exhibits the recently reported (beta alpha alpha)2 binding motif provides values for delta G, delta H, and delta S for each step in the repressor binding cycle. These studies show that, in the presence of corepressor, MetJ binds to a single metbox operator site with delta G = -7.7 kcal.mol-1, whereas in the absence of corepressor, the free energy of interaction with a single site is -5.8 kcal.mol-1. Cooperative interactions between two repressor molecules bound to two adjacent sites contribute an additional free energy of -1.3 kcal.mol-1 to binding at the second site. Binding is enthalpically unfavorable in the absence of the corepressor with delta H = +2.6 kcal.mol-1 but becomes exothermic with delta H = -4.6 kcal.mol-1 when corepressor is present. The heat capacity for the system decreases significantly by delta Cp = -290 cal.mol-1.K-1 on a per site basis when the protein binds to DNA, and interactions between repressor molecules bound to adjacent sites contribute a delta Cp = -800 cal.mol-1.K-1, indicating that solvent exclusion plays a significant role in binding in this system. The corepressor binds to the unbound repressor protein with a free energy of delta G = -6.0 kcal.mol-1 and to the MetJ-operator complex with delta G = -6.95 kcal.mol-1. Repressor binding to random-sequence DNA was estimated to occur with a free energy of -5.7 kcal.mol-1 in the presence of corepressor. These data clearly indicate that MetJ repressor dimer binds specifically to the central region of its 8 bp cognate metbox operator but recognizes partial operator sequences as short as 6 bp. Cooperativity in binding of adjacent MetJ dimers to a double metbox sequence is demonstrated to be important in determining the energetics of the interaction. Finally, the corepressor S-adenosylmethionine enhances the affinity of MetJ for its recognition site DNA by a factor of 25 and contributes significantly to the net exothermicity of repressor binding.

Authors
Hyre, DE; Spicer, LD
MLA Citation
Hyre, DE, and Spicer, LD. "Thermodynamic evaluation of binding interactions in the methionine repressor system of Escherichia coli using isothermal titration calorimetry." Biochemistry 34.10 (March 14, 1995): 3212-3221.
PMID
7880815
Source
pubmed
Published In
Biochemistry
Volume
34
Issue
10
Publish Date
1995
Start Page
3212
End Page
3221

High-level 2H/13C/15N labeling of proteins for NMR studies

The protein human carbonic anhydrase II (HCA II) has been isotopically labeled with 2H, 13C and 15N for high-resolution NMR assignment studies and pulse sequence development. To increase the sensitivity of several key 1H/13C/15N triple-resonance correlation experiments, 2H has been incorporated into HCA II in order to decrease the rates of 13C and 1HN T2 relaxation. NMR quantities of protein with essentially complete aliphatic 2H incorporation have been obtained by growth of E. coli in defined media containing D2O, [1,2-13C2, 99%] sodium acetate, and [15N, 99%] ammonium chloride. Complete aliphatic deuterium enrichment is optimal for 13C and 15N backbone NMR assignment studies, since the 13C and 1HN T2 relaxation times and, therefore, sensitivity are maximized. In addition, complete aliphatic deuteration increases both resolution and sensitivity by eliminating the differential 2H isotopic shift observed for partially deuterated CHnDm moieties. © 1995 ESCOM Science Publishers B.V.

Authors
Venters, RA; Huang, C-C; II, BTF; Trolard, R; Spicer, LD; Fierke, CA
MLA Citation
Venters, RA, Huang, C-C, II, BTF, Trolard, R, Spicer, LD, and Fierke, CA. "High-level 2H/13C/15N labeling of proteins for NMR studies." Journal of Biomolecular NMR 5.4 (1995): 339-344.
Source
scival
Published In
Journal of Biomolecular NMR
Volume
5
Issue
4
Publish Date
1995
Start Page
339
End Page
344
DOI
10.1007/BF00182275

A Test for Scaler Coupling between Heteronuclei Using Gradient-Enhanced Proton-Detected HMQC Spectroscopy

Authors
Brown, RA; Venters, RA; Tang, PPPZ; Spicer, LD
MLA Citation
Brown, RA, Venters, RA, Tang, PPPZ, and Spicer, LD. "A Test for Scaler Coupling between Heteronuclei Using Gradient-Enhanced Proton-Detected HMQC Spectroscopy." Journal of Magnetic Resonance, Series A 113.1 (1995): 117-119.
Source
scival
Published In
Journal of Magnetic Resonance - Series A
Volume
113
Issue
1
Publish Date
1995
Start Page
117
End Page
119
DOI
10.1006/jmra.1995.1064

Heteronuclear gradient-enhanced NMR for the study of 20-30kDa proteins: Application to human carbonic anhydrase II

Authors
Venters, RA; Spicer, LD
MLA Citation
Venters, RA, and Spicer, LD. "Heteronuclear gradient-enhanced NMR for the study of 20-30kDa proteins: Application to human carbonic anhydrase II." Techniques in Protein Chemistry 6.C (1995): 495-502.
Source
scival
Published In
Techniques in Protein Chemistry
Volume
6
Issue
C
Publish Date
1995
Start Page
495
End Page
502
DOI
10.1016/S1080-8914(06)80060-8

Use of 1HN-1HN NOEs to determine protein global folds in perdeuterated proteins

Authors
Venters, RA; Metzler, WJ; Spicer, LD; Mueller, L; II, BTF
MLA Citation
Venters, RA, Metzler, WJ, Spicer, LD, Mueller, L, and II, BTF. "Use of 1HN-1HN NOEs to determine protein global folds in perdeuterated proteins." Journal of the American Chemical Society 117.37 (1995): 9592-9593.
Source
scival
Published In
Journal of the American Chemical Society
Volume
117
Issue
37
Publish Date
1995
Start Page
9592
End Page
9593

NMR-derived solution conformations of a hybrid synthetic peptide containing multiple epitopes of envelope protein gp120 from the RF strain of human immunodeficiency virus.

Solution conformations of a 40-residue hybrid peptide containing T-helper epitopes and B-cell determinants from envelope glycoprotein gp120 of human immunodeficiency virus (HIV) have been investigated with NMR. Peptides of this general design are highly immunogenic and induce HIV-neutralizing antibodies and T-lymphocyte responses. The 16-residue N-terminal segment of the peptide contains a T-helper epitope, while the 24-residue C-terminal segment is derived from the V3 loop of HIV strain RF and contains epitopes that elicit neutralizing antibodies as well as T-cell responses. On the basis of 2D proton NMR spectra (COSY, TOCSY, and NOESY) of the peptide in aqueous solution, the resonances of nearly all hydrogens are assigned. The peptide is largely disordered, but specific medium-range NOEs demonstrate conformational preferences in certain regions. Part of the N-terminal segment exhibits nascent helical conformation, consistent with a finding that many T-cell antigens can be modeled as amphipathic helices. In the V3-derived segment of the peptide, one region shows evidence of a tight turn conformation, corresponding to a turn found previously in V3 peptides of HIV strains MN and IIIB. Other conformational features are also detected in the V3 region, such as a stretch of beta strand and a kink that may arise from side-chain interactions.

Authors
de Lorimier, R; Moody, MA; Haynes, BF; Spicer, LD
MLA Citation
de Lorimier, R, Moody, MA, Haynes, BF, and Spicer, LD. "NMR-derived solution conformations of a hybrid synthetic peptide containing multiple epitopes of envelope protein gp120 from the RF strain of human immunodeficiency virus." Biochemistry 33.8 (March 1, 1994): 2055-2062.
PMID
7509632
Source
pubmed
Published In
Biochemistry
Volume
33
Issue
8
Publish Date
1994
Start Page
2055
End Page
2062

NMR METHODS USED TO DERIVE SOLUTION CONFORMATIONS IN PEPTIDES

Authors
DELORIMIER, R; SPICER, LD
MLA Citation
DELORIMIER, R, and SPICER, LD. "NMR METHODS USED TO DERIVE SOLUTION CONFORMATIONS IN PEPTIDES." 1994.
Source
wos-lite
Published In
TECHNIQUES IN PROTEIN CHEMISTRY V
Publish Date
1994
Start Page
423
End Page
430

Proton NMR of Escherichia coli sulfite reductase: studies of the heme protein subunit with added ligands.

The heme protein subunit of sulfite reductase (SiR-HP; M(r) 64,000) from Escherichia coli as isolated contains the isobacteriochlorin siroheme exchange-coupled to a [4Fe-4S] cluster in the 2+ oxidation state. SiR-HP in the presence of a suitable electron donor can catalyze the six-electron reductions of sulfite to sulfide and nitrite to ammonia. Paramagnetic 1H NMR was used to study the low-spin complexes of SiR-HP formed by binding the exogenous inhibitor cyanide or the substrates sulfite and nitrite. As a model, the cyanide complex of purified siroheme was also prepared. The NMR spectrum of isolated ferric low-spin siroheme-CN is consistent with spin density being transferred into the a2u molecular orbital, an interaction which is symmetry-forbidden in porphyrins. The pattern of proton NMR shifts observed for isolated ferric low-spin siroheme-CN is very similar to those obtained for the protein-cyanide complex. NMR spectra of the cyanide complex of SiR-HP were obtained in all three accessible redox states. The pattern of hyperfine shifts observed for the one-electron and two-electron reduced cyanide complexes is typical of those seen for [4Fe-4S] clusters in the 2+ and 1+ oxidation states, respectively. Resonances arising from the beta-CH2 protons of cluster cysteines have been assigned for all complexes studied utilizing deuterium substitution. The cyanide-, sulfite-, and nitrite-ligated states possessed an almost identically shifted upfield cluster cysteine resonance whose presence indicates that covalent coupling exists between siroheme and cluster in solution. Data are also presented for the existence of a secondary anion binding site, the occupancy of which perturbs the oxidized SiR-HP NMR spectrum, where binding occurs at a rate much faster than that of ligand binding to heme.

Authors
Kaufman, J; Siegel, LM; Spicer, LD
MLA Citation
Kaufman, J, Siegel, LM, and Spicer, LD. "Proton NMR of Escherichia coli sulfite reductase: studies of the heme protein subunit with added ligands." Biochemistry 32.34 (August 31, 1993): 8782-8791.
PMID
8395881
Source
pubmed
Published In
Biochemistry
Volume
32
Issue
34
Publish Date
1993
Start Page
8782
End Page
8791

Proton NMR of Escherichia coli sulfite reductase: the unligated hemeprotein subunit.

The isolated hemeprotein subunit of sulfite reductase (SiR-HP) from Escherichia coli consists of a high spin ferric isobacteriochlorin (siroheme) coupled to a diamagnetic [4Fe-4S]2+ cluster. When supplied with an artificial electron donor, such as methyl viologen cation radical, SiR-HP can catalyze the six electron reductions of sulfite to sulfide and nitrite to ammonia. Thus, the hemeprotein subunit appears to represent the minimal protein structure required for multielectron reductase activity. Proton magnetic resonance spectra are reported for the first time on unligated SiR-HP at 300 MHz in all three redox states. The NMR spectrum of high spin ferric siroheme at pH 6.0 was obtained for the purpose of comparing its spectrum with that of oxidized SiR-HP. On the basis of line widths, T1 measurements, and 1D NOE experiments, preliminary assignments have been made for the oxidized enzyme in solution. The pH profile of oxidized SiR-HP is unusual in that a single resonance shows a 9 ppm shift over a range of only 3 pH units with an apparent pK = 6.7 +/- 0.2. Resonances arising from the beta-CH2 protons of cluster cysteines have been assigned using deuterium substitution for all redox states. One beta-CH2 resonance has been tentatively assigned to the bridging cysteine on the basis of chemical shift, T1, line width, and the presence of NOEs to protons from the siroheme ring. The observed pattern of hyperfine shifts can be used as a probe to measure the degree of coupling between siroheme and cluster in solution. The cluster iron sites of the resting (oxidized) enzyme are found to possess both positive and negative spin density which is in good agreement with Mossbauer results on frozen enzyme. The NMR spectrum of the 1-electron reduced form of SiR-HP is consistent with an intermediate spin (S = 1) siroheme. Intermediate spin Fe(II) hemes have only been previously observed in 4-coordinate model compounds. However, the amount of electron density transferred to the cluster, as measured by the isotropic shift of beta-CH2 resonances, is comparable to that present in the fully oxidized enzyme despite diminution of the total amount of unpaired spin density available. Addition of a second electron to SiR-HP, besides generating a reduced S = 1/2 cluster with both upfield and downfield shifted cysteine resonances, converts siroheme to the high spin (S = 2) ferrous state.(ABSTRACT TRUNCATED AT 400 WORDS)

Authors
Kaufman, J; Spicer, LD; Siegel, LM
MLA Citation
Kaufman, J, Spicer, LD, and Siegel, LM. "Proton NMR of Escherichia coli sulfite reductase: the unligated hemeprotein subunit." Biochemistry 32.11 (March 23, 1993): 2853-2867.
PMID
8457551
Source
pubmed
Published In
Biochemistry
Volume
32
Issue
11
Publish Date
1993
Start Page
2853
End Page
2867

Phosphorus 31 magnetic resonance spectroscopy of perifused human placental villi under varying oxygen concentrations.

OBJECTIVE: Initial phosphorus magnetic resonance spectroscopy observations on the oxygen metabolism of placental villi from normal term pregnancies are described. STUDY DESIGN: Villi were suspended in medium and perifused within a custom-designed 30 mm nuclear magnetic resonance probe in a superconducting vertical nuclear magnetic resonance magnet where pH, temperature, and oxygenation were monitored. RESULTS: Phosphorus resonances were observed from adenosine triphosphate, phosphomonoesters. inorganic phosphate, and phosphodiesters. No phosphocreatine signal was observed. The placental villus tissue responded to an increase in oxygen concentration of the perifusate with a rise in the adenosine triphosphate level and a concomitant decline in the inorganic phosphate and the phosphomonoester signals. CONCLUSION: The changes observed reflect continuing dynamic glycolysis and oxidative phosphorylation. The absence of a phosphocreatine peak suggests that aerobic pathways not driven by creatine kinase are important for placental metabolism. Our system demonstrates dynamic oxygen metabolism in perifused viable placental villus tissue by means of magnetic resonance spectroscopy.

Authors
Kay, HH; Hawkins, SR; Wang, Y; Mika, DE; Ribeiro, AA; Spicer, LD
MLA Citation
Kay, HH, Hawkins, SR, Wang, Y, Mika, DE, Ribeiro, AA, and Spicer, LD. "Phosphorus 31 magnetic resonance spectroscopy of perifused human placental villi under varying oxygen concentrations." Am J Obstet Gynecol 168.1 Pt 1 (January 1993): 246-252.
PMID
8420335
Source
pubmed
Published In
American Journal of Obstetrics & Gynecology
Volume
168
Issue
1 Pt 1
Publish Date
1993
Start Page
246
End Page
252

Phosphorus 31 magnetic resonance spectroscopy of perifused human placental villi under varying oxygen concentrations

Objective: Initial phosphorus magnetic resonance spectroscopy observations on the oxygen metabolism of placental villi from normal term pregnancies are described. Study design: Villi were suspended in medium and perifused within a custom-designed 30 mm nuclear magnetic resonance probe in a superconducting vertical nuclear magnetic resonance magnet where pH, temperature, and oxygenation were monitored. Results: Phosphorus resonances were observed from adenosine triphosphate, phosphomonoesters, inorganic phosphate, and phosphodiesters. No phosphocreatine signal was observed. The placental villus tissue responded to an increase in oxygen concentration of the perifusate with a rise in the adenosine triphosphate level and a concomitant decline in the inorganic phosphate and the phosphomonoester signals. Conclusion: The changes observed reflect continuing dynamic glycolysis and oxidative phosphorylation. The absence of a phosphocreatine peak suggests that aerobic pathways not driven by creatine kinase are important for placental metabolism. Our system demonstrates dynamic oxygen metabolism in perifused viable placental villus tissue by means of magnetic resonance spectroscopy.

Authors
Kay, HH; Hawkins, SR; Wang, Y; Mika, DE; Ribeiro, AA; Spicer, LD
MLA Citation
Kay, HH, Hawkins, SR, Wang, Y, Mika, DE, Ribeiro, AA, and Spicer, LD. "Phosphorus 31 magnetic resonance spectroscopy of perifused human placental villi under varying oxygen concentrations." American Journal of Obstetrics and Gynecology 168.1 I (1993): 246-252.
Source
scival
Published In
American Journal of Obstetrics and Gynecology
Volume
168
Issue
1 I
Publish Date
1993
Start Page
246
End Page
252

Comparative analysis of normal and growth-retarded placentas with phosphorus nuclear magnetic resonance spectroscopy.

OBJECTIVE: Phosphorus 31 magnetic resonance spectroscopy studies were carried out on placentas from normal vaginal and elective cesarean deliveries without antenatal complications and from pregnancies complicated by intrauterine growth retardation of unknown cause to determine differences. STUDY DESIGN: Perchloric acid extraction was performed on frozen tissue, and quantitative analysis was carried out for well-resolved resonances representing adenosine triphosphate, sugar phosphate, inorganic phosphorus, diphosphoglycerate, glycerophosphorylethanolamine, and glycerophosphorylcholine. RESULTS: Adenosine triphosphate levels were highest in the growth-retarded group. There were significantly higher levels of sugar phosphate, diphosphoglycerate, and glycerophosphorylcholine in the placentas of the growth-retarded pregnancies compared with those from normal placentas. CONCLUSION: These differences may represent a response to hypoxia and an increase in the amount of blood in the placenta. The results demonstrate the utility of nuclear magnetic resonance spectroscopy for studying the pathology of abnormal placentas to gain a better understanding of the pathology and represent early steps toward in vivo spectroscopic studies of the placenta.

Authors
Kay, HH; Hawkins, SR; Gordon, JD; Wang, Y; Ribeiro, AA; Spicer, LD
MLA Citation
Kay, HH, Hawkins, SR, Gordon, JD, Wang, Y, Ribeiro, AA, and Spicer, LD. "Comparative analysis of normal and growth-retarded placentas with phosphorus nuclear magnetic resonance spectroscopy." Am J Obstet Gynecol 167.2 (August 1992): 548-553.
PMID
1497068
Source
pubmed
Published In
American Journal of Obstetrics & Gynecology
Volume
167
Issue
2
Publish Date
1992
Start Page
548
End Page
553

A refocused and optimized HNCA: increased sensitivity and resolution in large macromolecules.

A 3D optimized, refocused HNCA experiment is described. It is demonstrated to yield a dramatic increase in sensitivity when applied to [13C, 15N]-labeled human carbonic anhydrase II, a 29-kDa protein. The reasons for the gain in sensitivity are discussed, and 3 distinct areas for further development are indicated.

Authors
Farmer, BT; Venters, RA; Spicer, LD; Wittekind, MG; Müller, L
MLA Citation
Farmer, BT, Venters, RA, Spicer, LD, Wittekind, MG, and Müller, L. "A refocused and optimized HNCA: increased sensitivity and resolution in large macromolecules." J Biomol NMR 2.2 (March 1992): 195-202.
PMID
1422152
Source
pubmed
Published In
Journal of Biomolecular NMR
Volume
2
Issue
2
Publish Date
1992
Start Page
195
End Page
202

Catalyst type and concentration dependence in catalytic transfer hydrogenolysis of α,β-unsaturated carbonyls and nitriles via ammonium formate

The catalytic reduction of a variety of α,β-unsaturated compounds into saturated analogs in the presence of other reducible moieties is described using ammonium formate as a hydrogen source. The rate dependence on the concentration of Pd-C catalyst as well as on 5% Pd-BaSO4 and Ra-Ni are also characterized.

Authors
Ram, S; Spicer, LD
MLA Citation
Ram, S, and Spicer, LD. "Catalyst type and concentration dependence in catalytic transfer hydrogenolysis of α,β-unsaturated carbonyls and nitriles via ammonium formate." Synthetic Communications 22.18 (1992): 2683-2690.
Source
scival
Published In
Synthetic Communications
Volume
22
Issue
18
Publish Date
1992
Start Page
2683
End Page
2690

Temperature and solvent dependent catalytic transfer hydrogenolysis in aromatic aldehydes and ketones via ammonium formate

Temperature control and solvent specification are used to reduce aromatic aldehydes and ketones to intermediate alcohols rather than methylene derivatives using HCO2NH4 as a catalytic hydrogen transfer agent. A mechanism for the catalytic reduction is proposed.

Authors
Ram, S; Spicer, LD
MLA Citation
Ram, S, and Spicer, LD. "Temperature and solvent dependent catalytic transfer hydrogenolysis in aromatic aldehydes and ketones via ammonium formate." Synthetic Communications 22.18 (1992): 2673-2681.
Source
scival
Published In
Synthetic Communications
Volume
22
Issue
18
Publish Date
1992
Start Page
2673
End Page
2681

Characterization of a microcarrier cell culture system for 23Na MR spectroscopy studies.

A MR spectroscopy method is described for the simultaneous discrimination and observation of sodium from the three compartments created by an intact cell monolayer. Results are reported for Madin Darby Canine Kidney (MDCK) cells, an epithelial-like continuous cell line, cultured on Cytodex 1 microcarrier beads and perfused with medium containing 6 mM dysprosium (III) tripolyphosphate [Dy(TPP)2(7-)] as shift reagent. The sodium spectrum shows three resonances which are assigned to the shifted intrabead (basolateral) and extrabead (apical) pools and the unshifted intracellular pool. Ouabain inhibition of the Na(+)-K(+)-ATPase cellular pump mechanism was used to demonstrate the sensitivity of the method for monitoring intracellular sodium. The supported MDCK cells in this system remained viable after exposure for 5 h to medium containing Dy(TPP)2(7-) at a concentration of 6 mM, as determined by trypan blue dye exclusion and by comparison of the log growth rate and ability to form domes in subsequent generations of exposed cells vs unexposed controls.

Authors
Shedd, SF; Spicer, LD
MLA Citation
Shedd, SF, and Spicer, LD. "Characterization of a microcarrier cell culture system for 23Na MR spectroscopy studies." NMR Biomed 4.5 (October 1991): 246-253.
PMID
1751347
Source
pubmed
Published In
Nmr in Biomedicine
Volume
4
Issue
5
Publish Date
1991
Start Page
246
End Page
253

Uniform 13C isotope labeling of proteins with sodium acetate for NMR studies: application to human carbonic anhydrase II.

Uniform double labeling of proteins for NMR studies can be prohibitively expensive, even with an efficient expression and purification scheme, due largely to the high cost of [13C6, 99%]glucose. We demonstrate here that uniformly (greater than 95%) 13C and 15N double-labeled proteins can be prepared for NMR structure/function studies by growing cells in defined media containing sodium [1,2-13C2, 99%]acetate as the sole carbon source and [15N, 99%]ammonium chloride as the sole nitrogen source. In addition, we demonstrate that this labeling scheme can be extended to include uniform carbon isotope labeling to any desired level (below 50%) by utilizing media containing equal amounts of sodium [1-13C, 99%]acetate and sodium [2-13C, 99%]acetate in conjunction with unlabeled sodium acetate. This technique is less labor intensive and more straightforward than labeling using isotope-enriched algal hydrolysates. These labeling schemes have been used to successfully prepare NMR quantities of isotopically enriched human carbonic anhydrase II. The activity and the 1H NMR spectra of the protein labeled by this technique are the same as those obtained from the protein produced from media containing labeled glucose; however, the cost of the sodium [1,2-13C2, 99%]acetate growth media is considerably less than the cost of the [13C6, 99%]glucose growth media. We report here the first published 13C and 15N NMR spectra of human carbonic anhydrase II as an important step leading to the assignment of this 29-kDa zinc metalloenzyme.

Authors
Venters, RA; Calderone, TL; Spicer, LD; Fierke, CA
MLA Citation
Venters, RA, Calderone, TL, Spicer, LD, and Fierke, CA. "Uniform 13C isotope labeling of proteins with sodium acetate for NMR studies: application to human carbonic anhydrase II." Biochemistry 30.18 (May 7, 1991): 4491-4494.
PMID
1902380
Source
pubmed
Published In
Biochemistry
Volume
30
Issue
18
Publish Date
1991
Start Page
4491
End Page
4494

Phosphorus 31 magnetic resonance spectroscopy of human placenta and quantitation with perchloric acid extracts.

Phosphorus 31 magnetic resonance spectroscopic studies of fresh placental tissue are reported that indicate resonances for adenosine triphosphate, inorganic phosphate, sugar phosphates-phosphomonoesters, and phosphodiesters. Perchloric acid extract methods were used to further characterize and quantitate phosphorous metabolites in term human placentas by phosphorus 31 magnetic resonance spectroscopy. The perchloric acid extracts give enhanced resolution of phosphorus signals and allow identification of other phosphorus metabolites including small amounts of phosphocreatine. Emphasis was placed on quantitating adenosine triphosphate levels in the acid extracts with the use of the external reference standard hexachlorocyclotriphosphazene in a coaxial capillary system. Adenosine triphosphate levels measured in this way ranged from 0.404 to 0.709 mumol per gram wet weight. Comparison with an internal standard method with phosphocreatine is also reported. Contribution to the measured high-energy phosphate pool from blood in the highly vascularized tissue was found to be relatively large and could range from 30% to 50% of the total adenosine triphosphate measured.

Authors
Kay, HH; Gordon, JD; Ribeiro, AA; Spicer, LD
MLA Citation
Kay, HH, Gordon, JD, Ribeiro, AA, and Spicer, LD. "Phosphorus 31 magnetic resonance spectroscopy of human placenta and quantitation with perchloric acid extracts." Am J Obstet Gynecol 164.1 Pt 1 (January 1991): 80-87.
PMID
1846063
Source
pubmed
Published In
American Journal of Obstetrics & Gynecology
Volume
164
Issue
1 Pt 1
Publish Date
1991
Start Page
80
End Page
87

Phosphorus 31 magnetic resonance spectroscopy of human placenta and quantitation with perchloric acid extracts

Phosphorus 31 magnetic resonance spectroscopic studies of fresh placental tissue are reported that indicate resonances for adenosine triphosphate, inorganic phosphate, sugar phosphates-phosphomonoesters, and phosphodiesters. Perchloric acid extract methods were used to further characterize and quantitate phosphorous metabolites in term human placentas by phosphorus 31 magnetic resonance spectroscopy. The perchloric acid extracts give enhanced resolution of phosphorus signals and allow identification of other phosphorus metabolites including small amounts of phosphocreatine. Emphasis was placed on quantitating adenosine triphosphate levels in the acid extracts with the use of the external reference standard hexachlorocyclotriphosphazene in a coaxial capillary system. Adenosine triphosphate levels measured in this way ranged from 0.404 to 0.709 μmol per gram wet weight. Comparison with an internal standard method with phosphocreatine is also reported. Contribution to the measured high-energy phosphate pool from blood in the highly vascularized tissue was found to be relatively large and could range from 30% to 50% of the total adenosine triphosphate measured. © 1991.

Authors
Kay, HH; Gordon, JD; Ribeiro, AA; Spicer, LD
MLA Citation
Kay, HH, Gordon, JD, Ribeiro, AA, and Spicer, LD. "Phosphorus 31 magnetic resonance spectroscopy of human placenta and quantitation with perchloric acid extracts." American Journal of Obstetrics and Gynecology 164.1 PART 1 (1991): 80-87.
Source
scival
Published In
American Journal of Obstetrics & Gynecology
Volume
164
Issue
1 PART 1
Publish Date
1991
Start Page
80
End Page
87

Use of gel filtration in the preparation of biological fluids for magnetic resonance spectroscopy.

Analysis of biological fluids by proton magnetic resonance spectroscopy is often complicated by dynamic range problems created from the large water resonance. Gel filtration chromatography is found to be a simple and nondestructive method for exchanging D2O for H2O and for removing low molecular weight molecules from both plasma and urine, significantly improving subsequent one- and two-dimensional MRS spectra.

Authors
Hoffman, DW; Venters, RA; Shedd, SF; Spicer, LD
MLA Citation
Hoffman, DW, Venters, RA, Shedd, SF, and Spicer, LD. "Use of gel filtration in the preparation of biological fluids for magnetic resonance spectroscopy." Magn Reson Med 13.3 (March 1990): 507-513.
PMID
2157933
Source
pubmed
Published In
Magnetic Resonance in Medicine
Volume
13
Issue
3
Publish Date
1990
Start Page
507
End Page
513

Synthesis of the labeled D1 receptor antagonist SCH 23390 using [11C]carbon dioxide.

A new synthesis is described for the production of the positron emitting radiopharmaceutical R-(+)-7-chloro-8-hydroxy-2,3,4,5-tetrahydro-3-N-[11C]methyl-1-phenyl-1H- 3-benzazepine (SCH 23390, 2a). This novel method involves reductive carboxylation, in which [11C]CO2 is reacted with the trimethylsilyl derivative of the desmethyl compound (SCH 24518, 1a) followed by treatment with lithium aluminum hydride, to afford no carrier added 11C-labeled SCH 23390. The procedure gave chemically and radiochemically pure 11C-labeled SCH 23390 in 53-72% radiochemical yield with an unoptimized specific activity of 40 Ci/mmol within 45-50 min from the end of bombardment.

Authors
Ram, S; Ehrenkaufer, RE; Spicer, LD
MLA Citation
Ram, S, Ehrenkaufer, RE, and Spicer, LD. "Synthesis of the labeled D1 receptor antagonist SCH 23390 using [11C]carbon dioxide." Int J Rad Appl Instrum A 40.5 (1989): 425-427.
PMID
2548974
Source
pubmed
Published In
International Journal of Radiation Applications and Instrumentation. Part A, Applied Radiation and Isotopes
Volume
40
Issue
5
Publish Date
1989
Start Page
425
End Page
427

Synthesis of 11C-labeled chlorpromazine directly from [11C]carbon dioxide.

Radiolabeled chlorpromazine was prepared by carboxylation of the N-trimethylsilyl derivative of norchlorpromazine with [11C]carbon dioxide, followed by in situ lithium aluminum hydride reduction. Radiochemical yields of 22-24% and radiochemical purities in the range of 93-98% were achieved.

Authors
Ram, S; Spicer, LD
MLA Citation
Ram, S, and Spicer, LD. "Synthesis of 11C-labeled chlorpromazine directly from [11C]carbon dioxide." Int J Rad Appl Instrum A 40.5 (1989): 413-416.
PMID
2548973
Source
pubmed
Published In
International Journal of Radiation Applications and Instrumentation. Part A, Applied Radiation and Isotopes
Volume
40
Issue
5
Publish Date
1989
Start Page
413
End Page
416

Direct incorporation of [11C]carbon dioxide for labeling bioactive molecules. An application to [11C] labeled tamoxifen

A one-pot synthesis of [11C] labeled tamoxifen has been developed via reductive carboxylation. In this approach, [11C]CO2 is reacted with the N-trimethylsilyl derivative of desmethyltamoxifen, followed by in situ sodium bis (2-methoxyethoxy)aluminum hydride reduction, to afford impure [11C] labeled tamoxifen, which, on purification over a basic alumina-silica gel column, provided pure [11C]tamoxifen in excellent radiochemical yield (65% to 84%) and radiochemical purity (> 99%). The specific activity of [11C]tamoxifen was 250-400 Ci/mmol at the end of bombardment.

Authors
Ram, S; Spicer, LD
MLA Citation
Ram, S, and Spicer, LD. "Direct incorporation of [11C]carbon dioxide for labeling bioactive molecules. An application to [11C] labeled tamoxifen." Journal of Labelled Compounds and Radiopharmaceuticals 27.6 (1989): 661-668.
Source
scival
Published In
Journal of Labelled Compounds and Radiopharmaceuticals
Volume
27
Issue
6
Publish Date
1989
Start Page
661
End Page
668

Reduction of aldehydes and ketones to methylen derivatives using ammonium formate as a catalytic hydrogen transfer agent

Various aromatic aldehydes and ketones were reduced to the corresponding hydrocarbons using ammonium formate as the hydrogen source. © 1988.

Authors
Ram, S; Spicer, LD
MLA Citation
Ram, S, and Spicer, LD. "Reduction of aldehydes and ketones to methylen derivatives using ammonium formate as a catalytic hydrogen transfer agent." Tetrahedron Letters 29.31 (1988): 3741-3744.
Source
scival
Published In
Tetrahedron Letters
Volume
29
Issue
31
Publish Date
1988
Start Page
3741
End Page
3744
DOI
10.1016/S0040-4039(00)82103-6

LASER INITIATED HOT CHEMISTRY WITH CATALYSTS

Authors
SPICER, LD
MLA Citation
SPICER, LD. "LASER INITIATED HOT CHEMISTRY WITH CATALYSTS." RADIOCHIMICA ACTA 43.2 (1988): 121-122.
Source
wos-lite
Published In
Radiochimica Acta
Volume
43
Issue
2
Publish Date
1988
Start Page
121
End Page
122

Magnetic field effects on surgical ligation clips.

Magnetic forces exerted on surgical clips and the magnetic resonance imaging distortion they create in phantoms and rabbits at magnetic field strengths of 1.5 Tesla were investigated. Results are reported for both ligation and aneurysm clips manufactured from three types of stainless steel as well as titanium, tantalum and niobium metals. Paramagnetism and eddy currents were measured in a customized moving Gouy balance. Direct measurements of other magnetic forces were carried out in a 1.5T MRI system. The titanium and tantalum clips showed the least interaction with the magnetic field, both in terms of forces exerted and the observed image distortion with the larger clips generating the larger interactions. The strongest field distortions and attractive forces occurred with 17-7PH stainless steel clips. These interactions were ferromagnetic in origin and of sufficient strength to present significant risk to patients having this type of clip present during an MRI scan.

Authors
Brown, MA; Carden, JA; Coleman, RE; McKinney, R; Spicer, LD
MLA Citation
Brown, MA, Carden, JA, Coleman, RE, McKinney, R, and Spicer, LD. "Magnetic field effects on surgical ligation clips." Magn Reson Imaging 5.6 (1987): 443-453.
PMID
3431354
Source
pubmed
Published In
Magnetic Resonance Imaging
Volume
5
Issue
6
Publish Date
1987
Start Page
443
End Page
453

Rapid debenzylation of N-benzylamino derivatives to amino-derivatives using ammonium formate as catalytic hydrogen transfer agent

Various N-benzyl derivatives of amino acids and amines were deprotected to the corresponding free amino acids and amines using ammonium formate as the hydrogen source. © 1987.

Authors
Ram, S; Spicer, LD
MLA Citation
Ram, S, and Spicer, LD. "Rapid debenzylation of N-benzylamino derivatives to amino-derivatives using ammonium formate as catalytic hydrogen transfer agent." Tetrahedron Letters 28.5 (1987): 515-516.
Source
scival
Published In
Tetrahedron Letters
Volume
28
Issue
5
Publish Date
1987
Start Page
515
End Page
516

NMR studies of combined lanthanide shift and relaxation agents for differential characterization of 23Na in a two-compartment model system.

Spin relaxation and chemical shifts by lanthanide chelate complexes are used to distinguish 23Na signals in a simulated two-compartment model. Both effects are significant in EDTA, DTPA, and TPP complexes of Gd and in the TPP complex of Dy. The simultaneous measurement of these properties is illustrated and represents a promising method for monitoring sodium concentrations and fluxes including fast transport components.

Authors
Brown, MA; Stenzel, TT; Ribeiro, AA; Drayer, BP; Spicer, LD
MLA Citation
Brown, MA, Stenzel, TT, Ribeiro, AA, Drayer, BP, and Spicer, LD. "NMR studies of combined lanthanide shift and relaxation agents for differential characterization of 23Na in a two-compartment model system." Magn Reson Med 3.2 (April 1986): 289-295.
PMID
2423838
Source
pubmed
Published In
Magnetic Resonance in Medicine
Volume
3
Issue
2
Publish Date
1986
Start Page
289
End Page
295

Computed tomographic evaluation of surgical clip artifact: tissue phantom and experimental animal assessment.

Surgical clips in postoperative patients create streak artifact on computed tomographic (CT) studies which often significantly degrade image quality. We have evaluated three types of surgical clips: tantalum, stainless steel, and titanium in a phantom and animal model to assess their relative CT artifact. Tantalum clips showed the greatest artifact, stainless steel intermediate, and titanium the least artifact. Artifact could be reduced with the use of faster scan times. The type of clip used may enter into surgical decision making depending upon the need for high resolution scanning to detect small pathological processes in the area of surgical clips.

Authors
Silverman, PM; Spicer, LD; McKinney, R; Feldman, DB
MLA Citation
Silverman, PM, Spicer, LD, McKinney, R, and Feldman, DB. "Computed tomographic evaluation of surgical clip artifact: tissue phantom and experimental animal assessment." Comput Radiol 10.1 (January 1986): 37-40.
PMID
3956187
Source
pubmed
Published In
Computerized Radiology
Volume
10
Issue
1
Publish Date
1986
Start Page
37
End Page
40

Promoting public understanding

Authors
Spicer, LD
MLA Citation
Spicer, LD. "Promoting public understanding." Chemical and Engineering News 64.48 (1986): 27-28.
Source
scival
Published In
Chemical & Engineering News
Volume
64
Issue
48
Publish Date
1986
Start Page
27
End Page
28

FT-IR study of nitric oxide chemisorbed on Rh/Al2O3

Chemisorption of NO on Rh/Al 2 O 3 surfaces has been examined by FT-IR. The spectra are assigned to two forms of Rh(NO) as well as the Rh(NO) 2 species. Apparent interconversion of the linear nitrosyl and dinitrosyl complexes is readily observed at room temperature. The dinitrosyl complex is characterized both by an invariant ratio of 1743- and 1825-cm -1 asymmetric and symmetric stretch bands with coverage and by isotopic data in 15 NO and the mixed 14 NO and 15 NO systems. Force constants for NO stretching motions and for NO/NO ligand interactions on Rh(NO) 2 have been used to successfully calculate the experimentally observed spectrum for the mixed isotope, dinitrosyl species. Thermal desorption data and displacement of adsorbed NO with CO are also reported. © 1985 American Chemical Society.

Authors
Liang, J; Wang, HP; Spicer, LD
MLA Citation
Liang, J, Wang, HP, and Spicer, LD. "FT-IR study of nitric oxide chemisorbed on Rh/Al2O3." Journal of Physical Chemistry 89.26 (December 1, 1985): 5840-5845.
Source
scopus
Published In
Journal of Physical Chemistry
Volume
89
Issue
26
Publish Date
1985
Start Page
5840
End Page
5845

FT-IR study of nitric oxide chemisorbed on Rh/Al2O3

Chemisorption of NO on Rh/Al2O3 surfaces has been examined by FT-IR. The spectra are assigned to two forms of Rh(NO) as well as the Rh(NO)2 species. Apparent interconversion of the linear nitrosyl and dinitrosyl complexes is readily observed at room temperature. The dinitrosyl complex is characterized both by an invariant ratio of 1743- and 1825-cm-1 asymmetric and symmetric stretch bands with coverage and by isotopic data in 15NO and the mixed 14NO and 15NO systems. Force constants for NO stretching motions and for NO/NO ligand interactions on Rh(NO)2 have been used to successfully calculate the experimentally observed spectrum for the mixed isotope, dinitrosyl species. Thermal desorption data and displacement of adsorbed NO with CO are also reported. © 1985 American Chemical Society.

Authors
Liang, J; Wang, HP; Spicer, LD
MLA Citation
Liang, J, Wang, HP, and Spicer, LD. "FT-IR study of nitric oxide chemisorbed on Rh/Al2O3." Journal of Physical Chemistry 89.26 (1985): 5840-5845.
Source
scival
Published In
Journal of Physical Chemistry
Volume
89
Issue
26
Publish Date
1985
Start Page
5840
End Page
5845

Determination of the spectrum of recoil energies for chlorine atoms generated by the 35Cl(n,γ) 36Cl nuclear process

Authors
Chang, J; Ferro, LJ; Spicer, LD
MLA Citation
Chang, J, Ferro, LJ, and Spicer, LD. "Determination of the spectrum of recoil energies for chlorine atoms generated by the 35Cl(n,γ) 36Cl nuclear process." The Journal of Chemical Physics 79.12 (1983): 6419-6421.
Source
scival
Published In
Journal of Chemical Physics
Volume
79
Issue
12
Publish Date
1983
Start Page
6419
End Page
6421

Characterization of the gas-phase components in equilibrium with the ionic compound ammonium trimethylsilyl sulfite: A new silanol source

Authors
Bennett, DW; Spicer, LD
MLA Citation
Bennett, DW, and Spicer, LD. "Characterization of the gas-phase components in equilibrium with the ionic compound ammonium trimethylsilyl sulfite: A new silanol source." Inorganic Chemistry 21.10 (1982): 3845-3847.
Source
scival
Published In
Inorganic Chemistry
Volume
21
Issue
10
Publish Date
1982
Start Page
3845
End Page
3847

The reaction between sulfur dioxide and hexamethyldisilazane. 2. Oxygen atom transfer from sulfur dioxide

The new reaction between sulfur dioxide and hexamethyldisilazane, which forms ((CH3)3Si)2O, (CH3)3SiNSO, and NH4(CH3)3SiOSO2, is characterized. In this reaction oxygen is transferred to silicon and sulfur from sulfur dioxide, but Si-N bonding is still partially retained. The solid product, ammonium trimethylsilyl sulfite, sublimes readily at ambient temperature but exhibits ionic properties. The variety of products and the overall reaction stoichiometry impose severe restrictions on possible reaction mechanisms. These constraints are discussed, and a consistent reaction scheme is proposed for this facile but unusual reaction. © 1982 American Chemical Society.

Authors
Bennett, DW; Spicer, LD
MLA Citation
Bennett, DW, and Spicer, LD. "The reaction between sulfur dioxide and hexamethyldisilazane. 2. Oxygen atom transfer from sulfur dioxide." Inorganic Chemistry 21.1 (1982): 410-413.
Source
scival
Published In
Inorganic Chemistry
Volume
21
Issue
1
Publish Date
1982
Start Page
410
End Page
413

The reaction between sulfur dioxide and hexamethyldisilazane. 3. The characterization of ammonium (trimethylsilyl)sulfite

The reaction between ((CH3)3Si)2NH and SO2 results in the formation of an ionic solid with empirical formula NH4(CH3)3SiOSO2 which readily "sublimes" at ambient temperature. Although (trimethylsilyl)ammonium bisulfite is a logical choice for a molecular formula, IR, NMR, and XPS data rule out the presence of RNH3+ and HSO3- ions. These data, along with a consideration of the solution behavior of this unique material, provide strong evidence that the substance is ammonium (trimethylsilyl)sulfite, with the silicon bonded to oxygen rather than sulfur. © 1981 American Chemical Society.

Authors
Bennett, DW; Spicer, LD
MLA Citation
Bennett, DW, and Spicer, LD. "The reaction between sulfur dioxide and hexamethyldisilazane. 3. The characterization of ammonium (trimethylsilyl)sulfite." Journal of the American Chemical Society 103.18 (1981): 5522-5526.
Source
scival
Published In
Journal of the American Chemical Society
Volume
103
Issue
18
Publish Date
1981
Start Page
5522
End Page
5526

Photoassistance in homogeneous catalysis: Direct modification of rates and selectivity of Wilkinson's Catalyst

Authors
Peterson, JR; Bennett, DW; Spicer, LD
MLA Citation
Peterson, JR, Bennett, DW, and Spicer, LD. "Photoassistance in homogeneous catalysis: Direct modification of rates and selectivity of Wilkinson's Catalyst." Journal of Catalysis 71.1 (1981): 223-225.
Source
scival
Published In
Journal of Catalysis
Volume
71
Issue
1
Publish Date
1981
Start Page
223
End Page
225

Formation of 1,1,1-trimethyl-N-sulfinylsilanamine from the direct reaction of SO2 with hexamethyldisilazane

Authors
Davis, JF; Spicer, LD
MLA Citation
Davis, JF, and Spicer, LD. "Formation of 1,1,1-trimethyl-N-sulfinylsilanamine from the direct reaction of SO2 with hexamethyldisilazane." Inorganic Chemistry 19.7 (1980): 2191-2192.
Source
scival
Published In
Inorganic Chemistry
Volume
19
Issue
7
Publish Date
1980
Start Page
2191
End Page
2192

Application of multistep deactivation processes in the interpretation of intermodular energy transfer following chemical activation by kinetic techniques

Interpretation of vibrational energy transfer following kinetically controlled chemical activation is refined by incorporating multistep deactivation processes into the RRKM treatment of the excited molecule. The functional form of the initial primary product energy distribution used is based on that suggested by Bunker. This model is applied in interpreting collisional energy transfer from cyclobutane-t, chemically activated by nuclear recoil reaction. New low pressure experimental data are used to estimate the average energy of the nascent cyclobutane-t and the average step sizes for energy transfer to He, N2, CO2, and parent on collision based on a stepladder deactivation model. Step sizes found for cyclobutane, He, N2, and CO2 are 10.0, 0.5, 2.0, and 5.0 kcal, respectively. © 1979 American Chemical Society.

Authors
Callahan, MB; Spicer, LD
MLA Citation
Callahan, MB, and Spicer, LD. "Application of multistep deactivation processes in the interpretation of intermodular energy transfer following chemical activation by kinetic techniques." Journal of Physical Chemistry 83.8 (1979): 1013-1016.
Source
scival
Published In
Journal of Physical Chemistry
Volume
83
Issue
8
Publish Date
1979
Start Page
1013
End Page
1016

Irradiation of benzene with 14CH+ and 14CH3+ ions

Authors
Erwin, WR; Gordon, BE; Spicer, LD; Lemmon, RM
MLA Citation
Erwin, WR, Gordon, BE, Spicer, LD, and Lemmon, RM. "Irradiation of benzene with 14CH+ and 14CH3+ ions." The Journal of Physical Chemistry 82.6 (March 1978): 654-656.
Source
crossref
Published In
Journal of Physical Chemistry
Volume
82
Issue
6
Publish Date
1978
Start Page
654
End Page
656
DOI
10.1021/j100495a007

Calculation of the average energy of recoil hot reactions. Hot hydrogen replacement reactions in alkane systems moderated with noble gases

The average energy of reaction for recoil hot species in a well scavenged system is defined explicitly and calculated for recoil tritium for hydrogen replacement reactions with cyclohexane and n-butane as a function of noble gas moderation. In general this average reaction energy is relatively independent of the composition of the system. However, in cases of high reactivity or low threshold energies for hot reaction where the primary reactive process competes significantly with thermal scavenging, more significant composition dependencies may be manifest. The generality of the method outlined is specifically dependent on the availability of information on the energy dependence of the cross sections for the reactions of interest.

Authors
Spicer, LD
MLA Citation
Spicer, LD. "Calculation of the average energy of recoil hot reactions. Hot hydrogen replacement reactions in alkane systems moderated with noble gases." Journal of the Chemical Society, Faraday Transactions 2: Molecular and Chemical Physics 74 (1978): 527-532.
Source
scival
Published In
Journal of the Chemical Society, Faraday Transactions 2: Molecular and Chemical Physics
Volume
74
Publish Date
1978
Start Page
527
End Page
532
DOI
10.1039/F29787400527

Determination of the spectrum of recoil energies for chlorine atoms generated by the 37Cl(n,γ) 38Cl nuclear process

Authors
Ferro, LJ; Spicer, LD
MLA Citation
Ferro, LJ, and Spicer, LD. "Determination of the spectrum of recoil energies for chlorine atoms generated by the 37Cl(n,γ) 38Cl nuclear process." The Journal of Chemical Physics 69.3 (1978): 1320-1321.
Source
scival
Published In
Journal of Chemical Physics
Volume
69
Issue
3
Publish Date
1978
Start Page
1320
End Page
1321

Characterization of the unimolecular behavior of recoil hot reaction products in inert bath gases. Application to c-C4H7T

A model for the kinetically controlled, nuclear recoil, chemical activation process is further developed to characterize the generation of excited cyclobutane and its subsequent unimolecular behavior. This approach specifically accounts for the overall effect of mixed bath gases in order to utilize previously reported pressure dependent data for cyclobutane in He, Ne, Xe, N2, and CF4. By incorporating appropriate relative energy transfer efficiencies from the activated molecule to the bath gases, a consistent interpretation for all of the experimental data is obtained. This model also provides information on the primary chemical activation process. The results indicate that ∼46% of the recoiling tritium energy is deposited into internal energy of the excited product cyclobutane-1 during the T for H replacement reaction and that the energy distribution of activated molecules is relatively independent of the bath gas present in these mixed bath gas systems. © 1978 American Institute of Physics.

Authors
Ferro, LJ; Spicer, LD
MLA Citation
Ferro, LJ, and Spicer, LD. "Characterization of the unimolecular behavior of recoil hot reaction products in inert bath gases. Application to c-C4H7T." The Journal of Chemical Physics 69.10 (1978): 4335-4340.
Source
scival
Published In
Journal of Chemical Physics
Volume
69
Issue
10
Publish Date
1978
Start Page
4335
End Page
4340

Irradiation of benzene with 14CH+ and 14CH3+ ions

Solid benzene at -196 °C was irradiated with 14CH+ and 14CH3+ ions at 10-eV kinetic energy. Yields were determined for the labeled hydrocarbon products: benzene, toluene, cycloheptatriene, diphenylmethane, biphenyl, and phenylcycloheptatriene. The radioactivity distributions between the ring and the methyl group of the toluene product were also determined. These results have been compared to those previously obtained with 14C+ and 14CH2+ ions. The comparisons have provided both insight into the reaction mechanisms and a tentative estimate of the distribution of the species (14CHx) that react with the benzene. © 1978 American Chemical Society.

Authors
Erwin, WR; Gordon, BE; Spicer, LD; Lemmon, RM
MLA Citation
Erwin, WR, Gordon, BE, Spicer, LD, and Lemmon, RM. "Irradiation of benzene with 14CH+ and 14CH3+ ions." Journal of Physical Chemistry 82.6 (1978): 654-656.
Source
scival
Published In
Journal of Physical Chemistry
Volume
82
Issue
6
Publish Date
1978
Start Page
654
End Page
656

Reactions of recoil generated chlorine-38 atoms with 2,3-dichlorohexafluoro-2-butene. Cis/trans isomerization accompanying chlorine for chlorine replacement

Gas-phase reactions of nuclear recoil generated chlorine-38 atoms with 2,3-dichlorohexafluoro-2-butene (2,3-DCHF2B) result predominantly in chlorine for chlorine substitution. The reaction proceeds with geometrical isomerization, and the resulting cis-trans branching ratios are dependent on the isomeric identity of the reactant and the concentration of inert diluent present. Mechanistic features responsible for the observed behavior are discussed in terms of both a thermal or near-thermal reaction path and a concurrent high-energy process which preferentially forms trans product from both cis and trans reactants. The rate for addition of near-thermal chlorine atoms to 2,3-DCHF2B relative to addition to ethylene was found to be ∼0.018. © 1978 American Chemical Society.

Authors
Stevens, DJ; Spicer, LD
MLA Citation
Stevens, DJ, and Spicer, LD. "Reactions of recoil generated chlorine-38 atoms with 2,3-dichlorohexafluoro-2-butene. Cis/trans isomerization accompanying chlorine for chlorine replacement." Journal of the American Chemical Society 100.11 (1978): 3295-3298.
Source
scival
Published In
Journal of the American Chemical Society
Volume
100
Issue
11
Publish Date
1978
Start Page
3295
End Page
3298

Characterization of hot chlorine atom reactions with hydrogen

The reaction of nuclear recoil generated chlorine atoms with hydrogen to produce hydrogen chloride was studied in the presence of ethylene and iodine scavengers. The yield behavior is presented for this reaction over a relative average translational energy range extending from a lower limit of ∼0.16 eV determined by the thermal scavenging efficiency of the system to several tens of electron volts. The hydrogen isotope effect for H2 and D2 reactants is explored over this same energy range and found to exhibit a cross over from a normal value of 2.3 to an inverse effect of 0.8 as the average reaction energy is increased. The relative kinetic behavior of the isotopic systems is interpreted in terms of a steady state non-Boltzmann formalism and comparison is made with reported results for corresponding fluorine atom reactions. © 1978 American Chemical Society.

Authors
Stevens, DJ; Spicer, LD
MLA Citation
Stevens, DJ, and Spicer, LD. "Characterization of hot chlorine atom reactions with hydrogen." Journal of Physical Chemistry 82.6 (1978): 627-632.
Source
scival
Published In
Journal of Physical Chemistry
Volume
82
Issue
6
Publish Date
1978
Start Page
627
End Page
632

Correlation between the average energy of reaction and system composition in recoil hot reaction studies

Authors
Stevens, DJ; Spicer, LD
MLA Citation
Stevens, DJ, and Spicer, LD. "Correlation between the average energy of reaction and system composition in recoil hot reaction studies." The Journal of Chemical Physics 66.11 (1977): 5253-5255.
Source
scival
Published In
Journal of Chemical Physics
Volume
66
Issue
11
Publish Date
1977
Start Page
5253
End Page
5255

Nuclear recoil chemical activation studies. Vibrational energy transfer from cyclobutane-t

A method is demonstrated for the determination of intermolecular energy transfer efficiencies in systems chemically activated by nuclear recoil reaction. Relative vibrational energy transfer efficiencies are determined for highly excited cyclobutane-t formed with ∼5 eV of internal energy in the hot tritium for hydrogen replacement reaction on cyclobutane in the presence of several inert bath gases. The pressure dependence of the hot yields is used to probe the overall reaction mechanism and results indicate that a sizable fraction of the hot reaction product does not undergo competitive unimolecular decomposition. The general systematics of these side reactions are discussed. From the composition dependence of the unimolecular reaction at a constant pressure of 800 torr, the relative energy transfer efficiencies for the respective bath gases are found to be C-C4H8, 1.0; CF 4, 1.05; N2, 0.32; He, 0.12; Ne, 0.24; Ar, 0.25; Kr, 0.31; Xe, 0.39. Simple collision models for the cyclobutane-noble gas cases suggest V-T transfer occurs most efficiently through delocalized interactions. Furthermore, angular momentum considerations indicate low impact parameter collisions are most effective in forming transition modes through which statistical redistribution of energy can occur. Copyright © 1977 American Institute of Physics.

Authors
Nogar, NS; Spicer, LD
MLA Citation
Nogar, NS, and Spicer, LD. "Nuclear recoil chemical activation studies. Vibrational energy transfer from cyclobutane-t." The Journal of Chemical Physics 66.8 (1977): 3624-3634.
Source
scival
Published In
Journal of Chemical Physics
Volume
66
Issue
8
Publish Date
1977
Start Page
3624
End Page
3634

Evidence for hydrogen abstraction as the rate determining step in the photochemical reaction of SO2 with alkanes

Authors
Smith, PP; Spicer, LD
MLA Citation
Smith, PP, and Spicer, LD. "Evidence for hydrogen abstraction as the rate determining step in the photochemical reaction of SO2 with alkanes." Chemosphere 6.7 (1977): 387-392.
Source
scival
Published In
Chemosphere
Volume
6
Issue
7
Publish Date
1977
Start Page
387
End Page
392

Potentiometric determination of solvation numbers and hydration constants for cations

A technique is developed for determining solvation numbers and hydration constants for metal ions. Stability constants are obtained that are essentially independent of the solution composition for a wide range of solvents. It is shown that two ROH molecules can take part in hydronium(-like) complex formation. Solvation numbers are obtained for H+, OH-, and organic acid anions as well as for divalent metal ions and their monochelates.

Authors
Uitert, CEV; Spicer, LD; Uitert, LGV
MLA Citation
Uitert, CEV, Spicer, LD, and Uitert, LGV. "Potentiometric determination of solvation numbers and hydration constants for cations." Journal of Physical Chemistry 81.1 (1977): 40-47.
Source
scival
Published In
Journal of Physical Chemistry
Volume
81
Issue
1
Publish Date
1977
Start Page
40
End Page
47

Kinetics and mechanism of recoil chlorine atom reactions with ethylene

Addition and abstraction are the major reactions observed between nuclear recoil generated chlorine atoms and ethylene. The addition reaction is characterized, and its relative efficiency is determined for low energy chlorine in systems containing H2 and C3F6 as competitive reactants. At low pressures, the unimolecular kinetics of an addition-decomposition process yielding HCl are examined, and the relative translational energy of the chlorine atoms which initiate that reaction is estimated. Hydrogen abstraction from ethylene is also explored in this system and found to be predominantly a low energy process in competition with addition. In the limits of high pressure and high moderation, the rate ratio of addition to abstraction for low energy chlorine atoms with ethylene is found to be 15.5 ± 0.5. Results for competitive addition reactions between C2H4 and C3F6 yield a rate ratio of 16 ± 2 favoring ethylene. The only additional reaction observed in pure ethylene corresponds to carbon-carbon bond scission and accounts for less than 1% of the total yield. © Copyright, 1977, by the American Chemical Society.

Authors
Stevens, DJ; Spicer, LD
MLA Citation
Stevens, DJ, and Spicer, LD. "Kinetics and mechanism of recoil chlorine atom reactions with ethylene." Journal of Physical Chemistry 81.13 (1977): 1217-1222.
Source
scival
Published In
Journal of Physical Chemistry
Volume
81
Issue
13
Publish Date
1977
Start Page
1217
End Page
1222

Energetics and Mechanism of the Recoil Tritium Replacement Reaction with Cyclobutane

Authors
NOGAB, NS; CALLAHAN, MB; SPICER, LEONAKDD
MLA Citation
NOGAB, NS, CALLAHAN, MB, and SPICER, LEONAKDD. "Energetics and Mechanism of the Recoil Tritium Replacement Reaction with Cyclobutane." Radiochimica Acta 23.2 (January 1, 1976).
Source
crossref
Published In
Radiochimica Acta
Volume
23
Issue
2
Publish Date
1976
DOI
10.1524/ract.1976.23.2.92

Dynamical features of the high energy isotope effect in chlorine atom reactions with hydrogen and deuterium

Authors
Stevens, DJ; Spicer, LD
MLA Citation
Stevens, DJ, and Spicer, LD. "Dynamical features of the high energy isotope effect in chlorine atom reactions with hydrogen and deuterium." The Journal of Chemical Physics 64.11 (1976): 4798-4800.
Source
scival
Published In
Journal of Chemical Physics
Volume
64
Issue
11
Publish Date
1976
Start Page
4798
End Page
4800

Vibration to translation energy transfer from excited cyclobutane chemically activated by nuclear recoil reaction [2]

Authors
Nogar, NS; Spicer, LD
MLA Citation
Nogar, NS, and Spicer, LD. "Vibration to translation energy transfer from excited cyclobutane chemically activated by nuclear recoil reaction [2]." Journal of Physical Chemistry 80.15 (1976): 1736-1738.
Source
scival
Published In
Journal of Physical Chemistry
Volume
80
Issue
15
Publish Date
1976
Start Page
1736
End Page
1738

Evidence for sulfur(1D) atom reactions involving 34S(n,.gamma.)35S nuclear recoil generated sulfur

Authors
Kremer, LN; Spicer, LD
MLA Citation
Kremer, LN, and Spicer, LD. "Evidence for sulfur(1D) atom reactions involving 34S(n.gamma.)35S nuclear recoil generated sulfur." Journal of the American Chemical Society 97.17 (August 1975): 5021-5022.
Source
crossref
Published In
Journal of the American Chemical Society
Volume
97
Issue
17
Publish Date
1975
Start Page
5021
End Page
5022
DOI
10.1021/ja00850a050

Evidence for S(1D) atom reactions involving 34S(n,γ)35S nuclear recoil generated sulfur [11]

Authors
Kremer, LN; Spicer, LD
MLA Citation
Kremer, LN, and Spicer, LD. "Evidence for S(1D) atom reactions involving 34S(n,γ)35S nuclear recoil generated sulfur [11]." Journal of the American Chemical Society 97.17 (1975): 5021-5022.
Source
scival
Published In
Journal of the American Chemical Society
Volume
97
Issue
17
Publish Date
1975
Start Page
5021
End Page
5022

Energy transfer studies from excited cyclobutane chemically activated by nuclear recoil reaction

Relative vibrational energy transfer efficiencies are determined for cyclobutane-t chemically activated to an average energy of 5 eV by recoil tritium replacement reaction. The pressure and composition dependence of the stabilization-decomposition ratio indicates relative efficiencies of 1.00, 1.05, and 0.32 for c-C4H8, CF4, and Ne bath gases. © 1975.

Authors
Nogar, NS; Dewey, JK; Spicer, LD
MLA Citation
Nogar, NS, Dewey, JK, and Spicer, LD. "Energy transfer studies from excited cyclobutane chemically activated by nuclear recoil reaction." Chemical Physics Letters 34.1 (1975): 98-104.
Source
scival
Published In
Chemical Physics Letters
Volume
34
Issue
1
Publish Date
1975
Start Page
98
End Page
104

Characterization of products from the photochemically induced reactions between SO2 and aliphatic hydrocarbons

Authors
Smith, PP; Spicer, LD
MLA Citation
Smith, PP, and Spicer, LD. "Characterization of products from the photochemically induced reactions between SO2 and aliphatic hydrocarbons." Chemosphere 4.3 (1975): 131-136.
Source
scival
Published In
Chemosphere
Volume
4
Issue
3
Publish Date
1975
Start Page
131
End Page
136

Gas chromatographic separation of hydrogen sulfide, carbonyl sulfide, and higher sulfur compounds with a single pass system

Authors
Kremer, L; Spicer, LD
MLA Citation
Kremer, L, and Spicer, LD. "Gas chromatographic separation of hydrogen sulfide, carbonyl sulfide, and higher sulfur compounds with a single pass system." Analytical Chemistry 45.11 (September 1973): 1963-1964.
Source
crossref
Published In
Analytical Chemistry
Volume
45
Issue
11
Publish Date
1973
Start Page
1963
End Page
1964
DOI
10.1021/ac60333a050

On the collision density in recoil hot atom systems. Effect of reactive events

Characteristics of the collisional distribution function for reactive hot atoms in nuclear recoil systems are examined and illustrated for the T + H2 system both unmoderated and moderated with argon. Reaction induced extrema are evident in the collision density of the unmoderated case. For this system depletion of hot atoms from the collisional distribution function due to reactive events is reflected significantly in the product yields even at high moderation. © 1973.

Authors
Malerich, CJ; Spicer, LD
MLA Citation
Malerich, CJ, and Spicer, LD. "On the collision density in recoil hot atom systems. Effect of reactive events." Chemical Physics Letters 18.3 (1973): 405-407.
Source
scival
Published In
Chemical Physics Letters
Volume
18
Issue
3
Publish Date
1973
Start Page
405
End Page
407

Deuterium Isotope Effect in Halogen Atom Reactions with Methane and Perdeuteriomethane at Energies above Thermal Thresholds

The origin of the isotope effect in the reaction of recoil chlorine atoms with methane and perdeuteriomethane was determined by diluting the systems with inert moderator to establish a unique steady-state collision distribution. The ratio of product yields from the hydrogenated system to those from the deuterated system as a function of moderator suggests that the isotope effect is primarily reactive in nature. The average probability of forming CH3Cl upon collision compared with CD3Cl is about 1.8 and that of forming CH2Cl compared with CD2Cl is about 1.6 in their respective systems.

Authors
Spicer, LD
MLA Citation
Spicer, LD. "Deuterium Isotope Effect in Halogen Atom Reactions with Methane and Perdeuteriomethane at Energies above Thermal Thresholds." Journal of the American Chemical Society 95.1 (1973): 51-53.
Source
scival
Published In
Journal of the American Chemical Society
Volume
95
Issue
1
Publish Date
1973
Start Page
51
End Page
53

Effects of inelastic processes on the collision distribution in recoil systems

The collisional distribution function for recoil hot atom systems is examined to determine the influence of specific inelastic processes on the collision density over the reactive energy range. The inelastic processes considered result from collisional dissociation of target molecules. In the case of recoil tritium reaction with deuterium gas, it was found that the collisional distribution function was lowered due to dissociative collisions. The modified collision density incorporating inelastic events was used in this system to calculate the hot yields of DT as a function of inert gas moderation for comparison with experimental data. Both the magnitude and shape of the experimental yield curve were well represented over the entire range of moderator concentrations.

Authors
Malerich, CJ; Spicer, LD
MLA Citation
Malerich, CJ, and Spicer, LD. "Effects of inelastic processes on the collision distribution in recoil systems." The Journal of Chemical Physics 59.4 (1973): 1577-1581.
Source
scival
Published In
Journal of Chemical Physics
Volume
59
Issue
4
Publish Date
1973
Start Page
1577
End Page
1581

The Reactive Isotope Effect in Nuclear Recoil 18F Reactions with CH4 and CD4 to Produce CH3F and CD3F

Authors
SPICER, LEONARDD; SIUDA, ANDRZEJ
MLA Citation
SPICER, LEONARDD, and SIUDA, ANDRZEJ. "The Reactive Isotope Effect in Nuclear Recoil 18F Reactions with CH4 and CD4 to Produce CH3F and CD3F." Radiochimica Acta 18.1 (January 1, 1972).
Source
crossref
Published In
Radiochimica Acta
Volume
18
Issue
1
Publish Date
1972
DOI
10.1524/ract.1972.18.1.16

Vibrational energy transfer in thermal methyl isocyanide isomerization. Relative cross sections in complex molecular systems

Relative energy transfer collision cross sections for several complex hydrocarbon and substituted hydrocarbon molecules have been determined in the methyl isocyanide thermal isomerization system. Particular interest was placed in the incremental cross sectional changes due to geometric isomerization in C6 hydrocarbons. Three generalizations are illustrated by the data. (1) Substitution for hydrogen in alkane molecules tends to increase their size. (2) Progressive branching of alkanes having constant carbon number causes a progressive decrease of the collision diameter. (3) Cyclization of the alkane chain decreases the effective size of the molecule. The energy transfer data are compared with viscosity-derived collision diameters where possible. A simple spherical model based on end-to-end carbon distances is proposed for systematizing the relative collision diameters of related complex molecules.

Authors
Spicer, LD; Rabinovitch, BS
MLA Citation
Spicer, LD, and Rabinovitch, BS. "Vibrational energy transfer in thermal methyl isocyanide isomerization. Relative cross sections in complex molecular systems." Journal of Physical Chemistry 74.12 (1970): 2445-2448.
Source
scival
Published In
Journal of Physical Chemistry
Volume
74
Issue
12
Publish Date
1970
Start Page
2445
End Page
2448

Energy transfer in thermal methyl isocyanide isomerization. A comprehensive investigation

The low-pressure thermal isomerization of methyl isocyanide has been studied at 280.5° in the presence of 109 different inert bath gases. Relative collisional activation-deactivation efficiencies β were measured. The attractive nature of the interaction is of importance: polarizability, dipole moment, and H-bonding ability of the bath molecule all seem to affect its efficiency. These experiments provide support for the view that vibrational energy transfer at high-energy levels of complex substrate molecules involves a quasi-statistical redistribution of internal energy of the collision complex. The efficiency increases in general with the number of transitional modes of the collision complex: a general correlation exists between β and the boiling point of the bath gas; but three subcorrelations are found for monatomic, diatomic and linear, and complex nonlinear molecules, respectively, which reflect the importance of dynamical considerations associated with angular momentum conservation in the energy-transfer process. Large amounts of energy are transferred per collision: 440 cm-1 for an inefficient bath molecule such as He, and in excess of 2000 cm-1 for operationally strong colliders such as the parent molecule. The role of the internal degrees of freedom of the bath molecule in energy transfer is not clear except for the parent molecule itself for which these seem to be active, but it is probable that lower vibration modes of some inerts play some role. Corrections to some earlier published data are given.

Authors
Chan, SC; Rabinovitch, BS; Bryant, JT; Spicer, LD; Fujimoto, T; Lin, YN; Pavlou, SP
MLA Citation
Chan, SC, Rabinovitch, BS, Bryant, JT, Spicer, LD, Fujimoto, T, Lin, YN, and Pavlou, SP. "Energy transfer in thermal methyl isocyanide isomerization. A comprehensive investigation." Journal of Physical Chemistry 74.17 (1970): 3160-3176.
Source
scival
Published In
Journal of Physical Chemistry
Volume
74
Issue
17
Publish Date
1970
Start Page
3160
End Page
3176

Energy transfer in thermal methyl isocyanide isomerization. Relative cross sections of fluoroalkanes and nitriles

The inert gas effect on the thermal isomerization of methyl isocyanide at 280.5° by the members of the homologous series of n-perfluoroalkanes and n-nitriles has been studied up to C6 in both cases. Relative collision diameters of these molecules, appropriate for the phenomenon of vibrational energy transfer involved, were obtained. ΔσCF2 = 0.54 Å is close to the value for ΔσCH2; higher perfluoroalkanes and alkanes are closely comparable in effective size. A dipolar orientation effect on the collision diameter of nitriles was observed. Some corrections and additions to earlier published values for hydrocarbons are described.

Authors
Chan, SC; Bryant, JT; Spicer, LD; Rabinovitch, BS
MLA Citation
Chan, SC, Bryant, JT, Spicer, LD, and Rabinovitch, BS. "Energy transfer in thermal methyl isocyanide isomerization. Relative cross sections of fluoroalkanes and nitriles." Journal of Physical Chemistry 74.10 (1970): 2058-2064.
Source
scival
Published In
Journal of Physical Chemistry
Volume
74
Issue
10
Publish Date
1970
Start Page
2058
End Page
2064

Dipolar orientation effect in collisional energy transfer [2]

Authors
Chan, SC; Rabinovitch, BS; Spicer, LD; Bryant, JT
MLA Citation
Chan, SC, Rabinovitch, BS, Spicer, LD, and Bryant, JT. "Dipolar orientation effect in collisional energy transfer [2]." Journal of Physical Chemistry 73.7 (1969): 2464--.
Source
scival
Published In
Journal of Physical Chemistry
Volume
73
Issue
7
Publish Date
1969
Start Page
2464-

Kinetic analysis of the reaction of hot chlorine atoms with alkanes; collisional dissociation of translationally excited products

The reactions with methane and ethane of hot chlorine atoms recoiling from the 40Ar (γ, p)39Cl nuclear reaction have been studied. Displacement reactions, analogous to those of hot hydrogen with alkanes, were found. In the case of methane, these gave CH339Cl and CH239Cl. Yields of these molecules show little pressure dependence, providing negative evidence for unimolecular decomposition due to internal excitation of primary products. A kinetic theory analysis of moderator data indicates that fast chlorine atoms are relatively less reactive than is hydrogen. Furthermore, energy transfer in inelastic collisions with methane appears to be relatively ineffective. The indicated weak coupling between translational and vibrational modes appears due to poor matching between the mean tune of collision and the C-H bond vibration period. This study appears to provide the first definite evidence for collisional decomposition of hot molecules. CH339Cl as formed by reaction of 39Cl with CH4 must be translationally excited. A kinetic theory analysis shows that this hot molecule has a considerable probability of breaking up on striking argon atoms. The likelihood of decomposition on collision with methane is, as expected, much less.

Authors
Spicer, L; Wolfgang, R
MLA Citation
Spicer, L, and Wolfgang, R. "Kinetic analysis of the reaction of hot chlorine atoms with alkanes; collisional dissociation of translationally excited products." The Journal of Chemical Physics 50.8 (1969): 3466-3476.
Source
scival
Published In
Journal of Chemical Physics
Volume
50
Issue
8
Publish Date
1969
Start Page
3466
End Page
3476

Systematics and mechanism of hot halogen reactions. Trends in total yield [9]

Authors
Spicer, L; Todd, JFJ; Wolfgang, R
MLA Citation
Spicer, L, Todd, JFJ, and Wolfgang, R. "Systematics and mechanism of hot halogen reactions. Trends in total yield [9]." Journal of the American Chemical Society 90.9 (1968): 2425-2426.
Source
scival
Published In
Journal of the American Chemical Society
Volume
90
Issue
9
Publish Date
1968
Start Page
2425
End Page
2426

Systematics and mechanism of hot halogen reactions. Product distribution [10]

Authors
Spicer, L; Wolfgang, R
MLA Citation
Spicer, L, and Wolfgang, R. "Systematics and mechanism of hot halogen reactions. Product distribution [10]." Journal of the American Chemical Society 90.9 (1968): 2426-2428.
Source
scival
Published In
Journal of the American Chemical Society
Volume
90
Issue
9
Publish Date
1968
Start Page
2426
End Page
2428

A new synthesis of 6-phenyl-2,3,5,6-tetrahydroimidazo[2,1-b]thiazole

A four-step synthesis of the anthelmintic dl-6-phenyl-2,3,5,6-tetrahydroimidazo[2,1-b]thiazole hydrochloride (tetramisole) from styrene oxide and ethylenimine is described. The key step is the reaction of α-phenyl-2-axiridineethanol with thiocyanic acid to give 2-imino-α-phenyl-3-thiazolidineethanol hydrochloride which proceeds in excellent yield.

Authors
Spicer, LD; Bullock, MW; Garber, M; Groth, W; Hand, JJ; Long, DW; Sawyer, JL; Wayne, RS
MLA Citation
Spicer, LD, Bullock, MW, Garber, M, Groth, W, Hand, JJ, Long, DW, Sawyer, JL, and Wayne, RS. "A new synthesis of 6-phenyl-2,3,5,6-tetrahydroimidazo[2,1-b]thiazole." Journal of Organic Chemistry 33.4 (1968): 1350-1353.
PMID
5641025
Source
scival
Published In
The Journal of Organic Chemistry
Volume
33
Issue
4
Publish Date
1968
Start Page
1350
End Page
1353

STRUCTURE OF STREPTOLYDIGIN.

Authors
RINEHART Jr, KL; BECK, JR; BORDERS, DB; EPSTEIN, WW; KINSTLE, TH; SPICER, LD; KRAUSS, D; BUTTON, AC
MLA Citation
RINEHART Jr, KL, BECK, JR, BORDERS, DB, EPSTEIN, WW, KINSTLE, TH, SPICER, LD, KRAUSS, D, and BUTTON, AC. "STRUCTURE OF STREPTOLYDIGIN." Antimicrobial agents and chemotherapy 161 (1963): 346-348. (Academic Article)
Source
manual
Published In
Antimicrobial agents and chemotherapy
Volume
161
Publish Date
1963
Start Page
346
End Page
348
Show More