Gary E. Martin

Last updated
Gary Martin
Born
Wilkinsburg, Pennsylvania, United States
NationalityAmerican
Alma mater University of Kentucky
University of Pittsburgh
Known for NMR Spectroscopy
Medicinal Chemistry
Scientific career
Fields Chemistry
Spectroscopy
Medicinal Chemistry
Institutions Merck Research Laboratories
Doctoral advisor George A. Digenis

Gary Martin is an American chemist and expert in the fields of both NMR spectroscopy and medicinal chemistry. He is a distinguished fellow at the Merck Research Laboratories. He is also a photographer specializing in the capture of images of lighthouses, especially under conditions of extreme weather. [1] [2]

Contents

Career

Martin holds a B.S. in Pharmacy from the University of Pittsburgh and a Ph.D. degree in Medicinal Chemistry/Pharmaceutical Sciences from the University of Kentucky. [3] He was a Professor of Medicinal Chemistry at the University of Houston from 1975–1989 and the director of the University of Houston NMR Facility between 1984–1989. He moved to the pharmaceutical industry in 1989 and worked at a number of pharmaceutical companies as described below. He has published more than 275 papers, invited reviews, and chapters and is a frequently invited lecturer at national and international NMR meetings.

Between 1989 and 1995 he worked at Burroughs Wellcome (later GlaxoSmithKline) (see reference 3) and worked on the development of new one- and two-dimensional NMR experiments for the solution of complex structural and spectral assignment problems. He developed new methods for the acquisition of submicromole and sub-nanomole NMR data for molecular structure characterization, especially work involving inverse-detected heteronuclear shift correlation techniques. These efforts led to collaborative development with Nalorac Cryogenics Corp. to develop micro inverse detection probes which facilitated the acquisition of HMQC spectra on samples to the level of 0.05 μmole for small (200-500 Da) molecule NMR. [4]

He moved to the Pharmacia corporation between 1996–2003 and ran the Rapid Structure Characterization Group. When Pharmacia was acquired by Pfizer, he served as the senior scientific consultant working on new methods development. He led the development of applications of unsymmetrical indirect covariance NMR, initially in an effort to eliminate artifacts and subsequently in the investigation of the mathematical combination of discretely-acquired 2D NMR data. The time savings for the latter was nearly a factor of 16 in time, with a 10-fold improvement in signal-to-noise ratios vs. directly acquiring an HSQC-TOCSY data set with the same sample. He conducted preliminary investigations into the utilization of indirect covariance NMR spectroscopy as an alternative means of evaluating NMR data for structure characterization and Computer-Assisted Structure Elucidation. He collaborated with a team of scientists at Advanced Chemistry Development, ACD/Labs, led by Antony John Williams, investigating the development of computational methods for automated structure verification and structure elucidation. [5] [6] [7] He developed “accordion-optimized” long-range heteronuclear shift correlation methods to provide experimental access to small long-range heteronuclear couplings for the characterization of proton-“deficient” molecular structures, [8] to experimentally access 4J heteronuclear couplings, to differentiate two-bond from three-bond long-range couplings to protonated carbons, to measure long-range heteronuclear couplings and to provide a reliable means of observing long-range proton-nitrogen correlations without concern for the variability of long-range proton nitrogen coupling constants. [9]

He also collaborated on the development of a new generation of sub-micro inverse detection probes with Nalorac Cryogenics Corporation designed to allow heteronuclear shift correlation experiments to be performed at levels down to 0.01 μmole for small molecules. The collaboration extended to a new generation of cold metal (at temperatures of 8K) 3 mm micro inverse detection probes. In 2006 he joined Schering-Plough and was responsible for the chemical structure characterization of impurities and degradants of candidate drug molecules in support of chemical process research. Schering Plough was acquired by Merck Research Laboratories in 2009. During his time at Merck he has continued to explore the limits of detection for low level samples by heteronuclear 2D NMR using newly developed 1.7 mm Micro CryoProbe™ technology. He has developed, in collaboration with ACD/Labs, and Bruker, unsymmetrical indirect covariance NMR spectroscopy, [10] [11] [12] exploring the calculation of hyphenated heteronuclear 2D correlation spectra. He has also continued collaborative investigations in the area of Computer-Assisted Structure Elucidation (CASE) with ACD/Labs. He has also explored the use of unsymmetrical indirect covariance NMR processing methods to define 13C-15N and 13C-13C heteronuclear connectivity networks.

He was named a 2016 Distinguished Graduate Alumnus of the University of Kentucky College of Pharmacy [13] He was the 2016 recipient of the James N. Shoolery Award to recognize individual contributions in the field of small molecule NMR [14] He was awarded the 2016 EAS Award for Outstanding Achievements in NMR. [15]

Research interests

His ongoing research interests have centered on the development of new NMR methods for the characterization of impurities and degradants of pharmaceuticals focusing on the exploration of new NMR probe technologies for the characterization of extremely small samples using heteronuclear 2D-NMR methods. His interests in this area were pivotal in the development of 3 mm and 1.7 mm probe technologies and he was also an early proponent of cryogenic probe capabilities., [16] [17]

He has had a long-standing interest in heteronuclear NMR and 2D long-range heteronuclear shift correlation in particular. He was among the first to exploit natural abundance long-range 1H-15N heteronuclear shift correlation experiments, those early reports leading to hundreds of published reports that are the subject of multiple reviews and chapters., [18] [19] More recently, his research interests have also led to the development of unsymmetrical indirect covariance NMR processing methods that have the potential for significant spectrometer time savings when experimental access to hyphenated 2D NMR. These methods also provide access to 13C-15N Heteronuclear Single Quantum Coherence-Heteronuclear Multiple Bond Coherence (HSQC-HMBC) correlation data that are experimentally inaccessible at natural abundance, and to HSQC-ADEQUATE correlation plots that allow carbon-carbon connectivity networks of molecules to be mapped without having to resort to the highly insensitive 13C-13C INADEQUATE experiment. In recent years Martin has extended his work into the application of residual dipolar couplings, residual chemical shift anisotropy and DFT calculations to demonstrate that, in combination, some of the most complex chemical structures could be elucidated and making unambiguous assignment essentially difficult or impossible. [20]

Related Research Articles

The nuclear Overhauser effect (NOE) is the transfer of nuclear spin polarization from one population of spin-active nuclei to another via cross-relaxation. A phenomenological definition of the NOE in nuclear magnetic resonance spectroscopy (NMR) is the change in the integrated intensity of one NMR resonance that occurs when another is saturated by irradiation with an RF field. The change in resonance intensity of a nucleus is a consequence of the nucleus being close in space to those directly affected by the RF perturbation.

In nuclear magnetic resonance (NMR) spectroscopy, the chemical shift is the resonant frequency of an atomic nucleus relative to a standard in a magnetic field. Often the position and number of chemical shifts are diagnostic of the structure of a molecule. Chemical shifts are also used to describe signals in other forms of spectroscopy such as photoemission spectroscopy.

<span class="mw-page-title-main">Nuclear magnetic resonance spectroscopy</span> Laboratory technique

Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy (MRS), is a spectroscopic technique based on re-orientation of atomic nuclei with non-zero nuclear spins in an external magnetic field. This re-orientation occurs with absorption of electromagnetic radiation in the radio frequency region from roughly 4 to 900 MHz, which depends on the isotopic nature of the nucleus and increased proportionally to the strength of the external magnetic field. Notably, the resonance frequency of each NMR-active nucleus depends on its chemical environment. As a result, NMR spectra provide information about individual functional groups present in the sample, as well as about connections between nearby nuclei in the same molecule. As the NMR spectra are unique or highly characteristic to individual compounds and functional groups, NMR spectroscopy is one of the most important methods to identify molecular structures, particularly of organic compounds.

<span class="mw-page-title-main">Solid-state nuclear magnetic resonance</span>

Solid-state nuclear magnetic resonance (ssNMR) is a spectroscopy technique used to characterize atomic-level structure and dynamics in solid materials. ssNMR spectra are broader due to nuclear spin interactions which can be categorized as dipolar coupling, chemical shielding, quadrupolar interactions, and j-coupling. These interactions directly affect the lines shapes of experimental ssNMR spectra which can be seen in powder and dipolar patterns. There are many essential solid-state techniques alongside advanced ssNMR techniques that may be applied to elucidate the fundamental aspects of solid materials. ssNMR is often combined with magic angle spinning (MAS) to remove anisotropic interactions and improve the sensitivity of the technique. The applications of ssNMR further extend to biology and medicine.

Carbon-13 (C13) nuclear magnetic resonance is the application of nuclear magnetic resonance (NMR) spectroscopy to carbon. It is analogous to proton NMR and allows the identification of carbon atoms in an organic molecule just as proton NMR identifies hydrogen atoms. 13C NMR detects only the 13
C
 isotope. The main carbon isotope, 12
C
 does not produce an NMR signal. Although ca. 1 mln. times less sensitive than 1H NMR spectroscopy, 13C NMR spectroscopy is widely used for characterizing organic and organometallic compounds, primarily because 1H-decoupled 13C-NMR spectra are more simple, have a greater sensitivity to differences in the chemical structure, and, thus, are better suited for identifying molecules in complex mixtures. At the same time, such spectra lack quantitative information about the atomic ratios of different types of carbon nuclei, because nuclear Overhauser effect used in 1H-decoupled 13C-NMR spectroscopy enhances the signals from carbon atoms with a larger number of hydrogen atoms attached to them more than from carbon atoms with a smaller number of H's, and because full relaxation of 13C nuclei is usually not attained, and the nuclei with shorter relaxation times produce more intense signals.

Nuclear magnetic resonance spectroscopy of proteins is a field of structural biology in which NMR spectroscopy is used to obtain information about the structure and dynamics of proteins, and also nucleic acids, and their complexes. The field was pioneered by Richard R. Ernst and Kurt Wüthrich at the ETH, and by Ad Bax, Marius Clore, Angela Gronenborn at the NIH, and Gerhard Wagner at Harvard University, among others. Structure determination by NMR spectroscopy usually consists of several phases, each using a separate set of highly specialized techniques. The sample is prepared, measurements are made, interpretive approaches are applied, and a structure is calculated and validated.

The heteronuclear single quantum coherence or heteronuclear single quantum correlation experiment, normally abbreviated as HSQC, is used frequently in NMR spectroscopy of organic molecules and is of particular significance in the field of protein NMR. The experiment was first described by Geoffrey Bodenhausen and D. J. Ruben in 1980. The resulting spectrum is two-dimensional (2D) with one axis for proton (1H) and the other for a heteronucleus, which is usually 13C or 15N. The spectrum contains a peak for each unique proton attached to the heteronucleus being considered. The 2D HSQC can also be combined with other experiments in higher-dimensional NMR experiments, such as NOESY-HSQC or TOCSY-HSQC.

<span class="mw-page-title-main">Two-dimensional nuclear magnetic resonance spectroscopy</span> Set of methods providing two-dimensional data

Two-Dimensional Nuclear Magnetic Resonance is an advanced spectroscopic technique that builds upon the capabilities of one-dimensional (1D) NMR by incorporating an additional frequency dimension. This extension allows for a more comprehensive analysis of molecular structures. In 2D NMR, signals are distributed across two frequency axes, providing improved resolution and separation of overlapping peaks, particularly beneficial for studying complex molecules. This technique identifies correlations between different nuclei within a molecule, facilitating the determination of connectivity, spatial proximity, and dynamic interactions.

Adriaan "Ad" Bax is a Dutch-American molecular biophysicist. He was born in the Netherlands and is the Chief of the Section on Biophysical NMR Spectroscopy at the National Institutes of Health. He is known for his work on the methodology of biomolecular NMR spectroscopy. He is a corresponding member of the Royal Netherlands Academy of Arts and Sciences, a member of the National Academy of Sciences, a fellow of the American Academy of Arts and Sciences, and a Foreign Member of the Royal Society.

Nuclear magnetic resonance decoupling is a special method used in nuclear magnetic resonance (NMR) spectroscopy where a sample to be analyzed is irradiated at a certain frequency or frequency range to eliminate or partially the effect of coupling between certain nuclei. NMR coupling refers to the effect of nuclei on each other in atoms within a couple of bonds distance of each other in molecules. This effect causes NMR signals in a spectrum to be split into multiple peaks. Decoupling fully or partially eliminates splitting of the signal between the nuclei irradiated and other nuclei such as the nuclei being analyzed in a certain spectrum. NMR spectroscopy and sometimes decoupling can help determine structures of chemical compounds.

<span class="mw-page-title-main">Antony John Williams</span> British chemist

Antony John Williams is a British chemist and expert in the fields of both nuclear magnetic resonance (NMR) spectroscopy and cheminformatics at the United States Environmental Protection Agency. He is the founder of the ChemSpider website that was purchased by the Royal Society of Chemistry in May 2009. He is a science blogger and an author.

Nuclear magnetic resonance crystallography is a method which utilizes primarily NMR spectroscopy to determine the structure of solid materials on the atomic scale. Thus, solid-state NMR spectroscopy would be used primarily, possibly supplemented by quantum chemistry calculations, powder diffraction etc. If suitable crystals can be grown, any crystallographic method would generally be preferred to determine the crystal structure comprising in case of organic compounds the molecular structures and molecular packing. The main interest in NMR crystallography is in microcrystalline materials which are amenable to this method but not to X-ray, neutron and electron diffraction. This is largely because interactions of comparably short range are measured in NMR crystallography.

Nucleic acid NMR is the use of nuclear magnetic resonance spectroscopy to obtain information about the structure and dynamics of nucleic acid molecules, such as DNA or RNA. It is useful for molecules of up to 100 nucleotides, and as of 2003, nearly half of all known RNA structures had been determined by NMR spectroscopy.

Triple resonance experiments are a set of multi-dimensional nuclear magnetic resonance spectroscopy (NMR) experiments that link three types of atomic nuclei, most typically consisting of 1H, 15N and 13C. These experiments are often used to assign specific resonance signals to specific atoms in an isotopically-enriched protein. The technique was first described in papers by Ad Bax, Mitsuhiko Ikura and Lewis Kay in 1990, and further experiments were then added to the suite of experiments. Many of these experiments have since become the standard set of experiments used for sequential assignment of NMR resonances in the determination of protein structure by NMR. They are now an integral part of solution NMR study of proteins, and they may also be used in solid-state NMR.

Nuclear magnetic resonance chemical shift re-referencing is a chemical analysis method for chemical shift referencing in biomolecular nuclear magnetic resonance (NMR). It has been estimated that up to 20% of 13C and up to 35% of 15N shift assignments are improperly referenced. Given that the structural and dynamic information contained within chemical shifts is often quite subtle, it is critical that protein chemical shifts be properly referenced so that these subtle differences can be detected. Fundamentally, the problem with chemical shift referencing comes from the fact that chemical shifts are relative frequency measurements rather than absolute frequency measurements. Because of the historic problems with chemical shift referencing, chemical shifts are perhaps the most precisely measurable but the least accurately measured parameters in all of NMR spectroscopy.

Protein chemical shift re-referencing is a post-assignment process of adjusting the assigned NMR chemical shifts to match IUPAC and BMRB recommended standards in protein chemical shift referencing. In NMR chemical shifts are normally referenced to an internal standard that is dissolved in the NMR sample. These internal standards include tetramethylsilane (TMS), 4,4-dimethyl-4-silapentane-1-sulfonic acid (DSS) and trimethylsilyl propionate (TSP). For protein NMR spectroscopy the recommended standard is DSS, which is insensitive to pH variations. Furthermore, the DSS 1H signal may be used to indirectly reference 13C and 15N shifts using a simple ratio calculation [1]. Unfortunately, many biomolecular NMR spectroscopy labs use non-standard methods for determining the 1H, 13C or 15N “zero-point” chemical shift position. This lack of standardization makes it difficult to compare chemical shifts for the same protein between different laboratories. It also makes it difficult to use chemical shifts to properly identify or assign secondary structures or to improve their 3D structures via chemical shift refinement. Chemical shift re-referencing offers a means to correct these referencing errors and to standardize the reporting of protein chemical shifts across laboratories.

ShiftX is a freely available web server for rapidly calculating protein chemical shifts from protein X-ray coordinates. Protein chemical shift prediction is particularly useful in verifying protein chemical shift assignments, adjusting mis-referenced chemical shifts, refining NMR protein structures and assisting with the NMR assignment of unassigned proteins that have either had their structures determined by X-ray or NMR methods.

Nitrogen-15 nuclear magnetic resonance spectroscopy is a version of nuclear magnetic resonance spectroscopy that examines samples containing the 15N nucleus. 15N NMR differs in several ways from the more common 13C and 1H NMR. To circumvent the difficulties associated with measurement of the quadrupolar, spin-1 14N nuclide, 15N NMR is employed in samples for detection since it has a ground-state spin of ½. Since14N is 99.64% abundant, incorporation of 15N into samples often requires novel synthetic techniques.

<span class="mw-page-title-main">Lyndon Emsley</span> British chemist

David Lyndon Emsley FRSC is a British chemist specialising in solid-state nuclear magnetic resonance and a professor at EPFL. He was awarded the 2012 Grand Prix Charles-Leopold Mayer of the French Académie des Sciences and the 2015 Bourke Award of the Royal Society of Chemistry.

<span class="mw-page-title-main">Geoffrey Bodenhausen</span> French chemist

Geoffrey Bodenhausen is a French chemist specializing in nuclear magnetic resonance, being highly cited in his field. He is a Corresponding member of the Royal Netherlands Academy of Arts and Sciences and a Fellow of the American Physical Society. He is professeur émérite at the Department of Chemistry at the École Normale Supérieure (ENS) in Paris and professeur honoraire at the Laboratory of Biomolecular Magnetic Resonance of the École Polytechnique Fédérale de Lausanne (EPFL). He is a member of the editorial board of the journal Progress in Nuclear Magnetic Resonance Spectroscopy. He is the chair of the editorial board of the journal Magnetic Resonance.

References

  1. ↑ Awards, Publications and Recognition for Gary Martin Photography
  2. ↑ Gary Martin Photography biography
  3. ↑ Interview with Gary Martin at Reactive Reports, by David Bradley; posted February 7, 2006; retrieved April 18, 2011
  4. ↑ Martin, G.E.; Crouch, R.C.; Zens, A.P. (1998). "Gradient submicro inverse detection: rapid acquisition of inverse-detected heteronuclear chemical shift correlation data on submicromole quantities of material". Magnetic Resonance in Chemistry. 36 (7): 551–557. doi:10.1002/(SICI)1097-458X(199807)36:7<551::AID-OMR332>3.0.CO;2-F. S2CID   98408800.
  5. ↑ Martin, G.E.; Hadden, C.E.; Russell, D.J.; Kaluzny, B.D.; Guido, J.E.; Duholke, W.K.; Stiemsma, B.A.; Thamann, T.J.; Crouch, R.C.; Blinov, K.A.; Elyashberg, M.E.; Martirosian, E.R.; Molodtsov, S.G.; Williams, A.J.; Schiff Jr, P.L. (2002). "Identification of Degradants of a Complex Alkaloid Using NMR Cryoprobe Technology and ACD/Structure Elucidator". J. Heterocyclic Chem. 39 (6): 1241–1250. doi:10.1002/jhet.5570390619.
  6. ↑ Blinov, K.; Elyashberg, M.; Martirosian, E. R.; Molodtsov, S. G.; Williams, A. J.; Sharaf, M. H. M.; Schiff, P. L.; Crouch, R. C.; Martin, G. E.; Hadden, C. E.; Guido, J. E. (2003). "Quindolinocryptotackieine: The Elucidation of a Novel Indoloquinoline Alkaloid Structure through the Use of Computer-Assisted Structure Elucidation and 2D-NMR". Magn. Reson. Chem. 41 (8): 577–584. doi: 10.1002/mrc.1227 .
  7. ↑ Elyashberg, M. E.; Blinov, K. A.; Martirosian, E. R.; Molodtsov, S. G.; Williams, A. J.; Martin, G. E. (2003). "Automated Structure Elucidation – The Benefits of a Symbiotic Relationship between the Spectroscopist and the Expert System". J. Heterocyclic Chem. 40 (6): 1017–1029. doi:10.1002/jhet.5570400610.
  8. ↑ Hadden, C.E.; Martin, G.E.; Krishnamurthy, V.V. (1999). "Improved Performance Accordion Heteronuclear Multiple-Bond Correlation Spectroscopy—IMPEACH-MBC". Journal of Magnetic Resonance. 140 (1): 274–280. Bibcode:1999JMagR.140..274H. doi:10.1006/jmre.1999.1840. PMID   10479572.
  9. ↑ Martin, G.E.; Hadden, C.E. (2000). "Long-range 1H-15N heteronuclear shift correlation at natural abundance (review)". J. Nat. Prod. 63 (4): 543–85. doi:10.1021/np9903191. PMID   10785437.
  10. ↑ Blinov, K.A.; Williams, A.J.; Hilton, B.D.; Irish, P.A.; Martin, G.E. (2007). "The Use of Unsymmetrical Indirect Covariance NMR Methods to Obtain the Equivalent of HSQC-NOESY Data". Magn. Reson. Chem. 45 (7): 544–546. doi:10.1002/mrc.1998. PMID   17437315. S2CID   46106410.
  11. ↑ Martin, G. E.; Irish, P. A.; Hilton, B. D.; Blinov, K. A.; Williams, A. J. (2007). "Utilizing Unsymmetrical Indirect Covariance Processing to Define 15N-13C Connectivity Networks". Magn. Reson. Chem. 45 (8): 624–627. doi:10.1002/mrc.2029. PMID   17563910. S2CID   34281811.
  12. ↑ Martin, G.E.; Hilton, B.D.; Irish, P.A.; Blinov, K.A.; Williams, A.J. (2007). "Application of Unsymmetrical Indirect Covariance NMR Methods to the Computation of 13C-15N HSQC-IMPEACH and 13C-15N HMBC-IMPEACH Correlation Spectra of the Alkaloid Vincamine". Magn. Reson. Chem. 45 (10): 883–888. doi:10.1002/mrc.2064. PMID   17729230. S2CID   41359162.
  13. ↑ "Hall of Distinguished Alumni | UK College of Pharmacy".
  14. ↑ "Shoolery Award Recipient - SMASH - Small Molecule NMR Conference".
  15. ↑ "2016 EAS Award for Outstanding Achievements in NMR". Eastern Analytical Symposium. February 2016.
  16. ↑ Martin, G.E.; Hadden, C.E. (1999). "Comparison of 1.7 mm Submicro and 3 mm Micro Gradient NMR Probes for the Acquisition of 1H-13C and 1H-15N Heteronuclear Shift Correlation Data". Magn. Reson. Chem. 37 (10): 721–729. doi:10.1002/(SICI)1097-458X(199910)37:10<721::AID-MRC525>3.0.CO;2-Z. S2CID   98184044.
  17. ↑ Russell, D.J.; Hadden, C.E.; Martin, G.E.; Gibson, A.A.; Zens, A.P.; Carolan, J.L. (2000). "A Comparison of Inverse-Detected Heteronuclear NMR Performance: Conventional 3 mm vs. 3 mm Cryogenic Probe Performance". J. Nat. Prod. 63 (8): 1047–1049. doi:10.1021/np0003140. PMID   10978194.
  18. ↑ G. E. Martin, M. Solntseva, and A. J. Williams "Applications of 15N NMR in Alkaloid Chemistry" Modern Alkaloids, E. Fattorusso and O. Taglialatela-Scafati, Wiley-VCH, New York, 2007, pp. 411-476 doi : 10.1002/9783527621071.ch14
  19. ↑ Crouch, R.C.; Davis, A.O.; Spitzer, T.D.; Martin, G.E.; Sharaf, M.H.M.; Schiff, P.L.; Phoebe, C.H.; Tackie, A.N. (1995). "Elucidation of the Structure of Quindolinone, a Minor Alkaloid of Cryptolepis sanguinolenta: Submilligram 1H-13C and 1H-15N Heteronuclear Shift Correlation Experiments Using Micro Inverse-Detection". J. Heterocyclic Chem. 32 (3): 1077–1080. doi:10.1002/jhet.5570320369.
  20. ↑ Liu, Y.; Sauri, J.; Mavers, E.; Peczuh, M.W.; Hiemstra, H.; Clardy, J.; Martin, G.E.; Williamson, R.T. (2017). "Unequivocal determination of complex molecular structures using anisotropic NMR measurements". Science. 356 (6333): eaam5349. doi: 10.1126/science.aam5349 . PMC   6596297 . PMID   28385960.
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