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Dai D, Wang X, Liu Y, Yang XL, Glaubitz C, Denysenkov V, He X, Prisner T, Mao J. Room-temperature dynamic nuclear polarization enhanced NMR spectroscopy of small biological molecules in water. Nat Commun 2021; 12:6880. [PMID: 34824218 PMCID: PMC8616939 DOI: 10.1038/s41467-021-27067-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Accepted: 11/01/2021] [Indexed: 11/15/2022] Open
Abstract
Nuclear magnetic resonance (NMR) spectroscopy is a powerful and popular technique for probing the molecular structures, dynamics and chemical properties. However the conventional NMR spectroscopy is bottlenecked by its low sensitivity. Dynamic nuclear polarization (DNP) boosts NMR sensitivity by orders of magnitude and resolves this limitation. In liquid-state this revolutionizing technique has been restricted to a few specific non-biological model molecules in organic solvents. Here we show that the carbon polarization in small biological molecules, including carbohydrates and amino acids, can be enhanced sizably by in situ Overhauser DNP (ODNP) in water at room temperature and at high magnetic field. An observed connection between ODNP 13C enhancement factor and paramagnetic 13C NMR shift has led to the exploration of biologically relevant heterocyclic compound indole. The QM/MM MD simulation underscores the dynamics of intermolecular hydrogen bonds as the driving force for the scalar ODNP in a long-living radical-substrate complex. Our work reconciles results obtained by DNP spectroscopy, paramagnetic NMR and computational chemistry and provides new mechanistic insights into the high-field scalar ODNP.
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Affiliation(s)
- Danhua Dai
- Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, 60438, Frankfurt am Main, Germany
- Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt, 60438, Frankfurt am Main, Germany
| | - Xianwei Wang
- Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, 200062, China
- College of Science, Zhejiang University of Technology, Hangzhou, Zhejiang, 310023, China
| | - Yiwei Liu
- Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, 200062, China
| | - Xiao-Liang Yang
- Jiangsu Key Laboratory of Advanced Organic Materials, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China
| | - Clemens Glaubitz
- Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt, 60438, Frankfurt am Main, Germany
- Institute of Biophysical Chemistry, Goethe University Frankfurt, 60438, Frankfurt am Main, Germany
| | - Vasyl Denysenkov
- Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, 60438, Frankfurt am Main, Germany
- Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt, 60438, Frankfurt am Main, Germany
| | - Xiao He
- Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, 200062, China.
- NYU-ECNU Center for Computational Chemistry at NYU Shanghai, Shanghai, 200062, China.
| | - Thomas Prisner
- Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, 60438, Frankfurt am Main, Germany
- Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt, 60438, Frankfurt am Main, Germany
| | - Jiafei Mao
- Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt, 60438, Frankfurt am Main, Germany.
- Institute of Biophysical Chemistry, Goethe University Frankfurt, 60438, Frankfurt am Main, Germany.
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Chen HY, Tycko R. Temperature-Dependent Nuclear Spin Relaxation Due to Paramagnetic Dopants Below 30 K: Relevance to DNP-Enhanced Magnetic Resonance Imaging. J Phys Chem B 2018; 122:11731-11742. [PMID: 30277390 PMCID: PMC6465147 DOI: 10.1021/acs.jpcb.8b07958] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Dynamic nuclear polarization (DNP) can increase nuclear magnetic resonance (NMR) signal strengths by factors of 100 or more at low temperatures. In magnetic resonance imaging (MRI), signal enhancements from DNP potentially lead to enhancements in image resolution. However, the paramagnetic dopants required for DNP also reduce nuclear spin relaxation times, producing signal losses that may cancel the signal enhancements from DNP. Here we investigate the dependence of 1H NMR relaxation times, including T1ρ and T2, under conditions of Lee-Goldburg 1H-1H decoupling and pulsed spin locking, on temperature and dopant concentration in frozen solutions that contain the trinitroxide compound DOTOPA. We find that relaxation times become longer at temperatures below 10 K, where DOTOPA electron spins become strongly polarized at equilibrium in a 9.39 T magnetic field. We show that the dependences of relaxation times on temperature and DOTOPA concentration can be reproduced qualitatively (although not quantitatively) by detailed simulations of magnetic field fluctuations due to flip-flop transitions in a system of dipole-coupled electron spin magnetic moments. These results have implications for ongoing attempts to reach submicron resolution in inductively detected MRI at very low temperatures.
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Affiliation(s)
- Hsueh-Ying Chen
- Laboratory of Chemical Physics National Institute of Diabetes and Digestive and Kidney Diseases , National Institutes of Health , Bethesda , Maryland 20892-0520 , United States
| | - Robert Tycko
- Laboratory of Chemical Physics National Institute of Diabetes and Digestive and Kidney Diseases , National Institutes of Health , Bethesda , Maryland 20892-0520 , United States
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Krunić A, Orjala J. Application of high-field NMR spectroscopy for characterization and quantitation of submilligram quantities of isolated natural products. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2015; 53:1043-50. [PMID: 26289113 PMCID: PMC4752180 DOI: 10.1002/mrc.4304] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Revised: 06/18/2015] [Accepted: 06/27/2015] [Indexed: 05/13/2023]
Abstract
We have investigated and compared a number of sample conditions on different NMR platforms in the search of maximum SNR and optimal experiment time efficiency for structure elucidation and quantitation of natural products. Using restricted volume 3 mm Shigemi microcell assembly in conjunction with a 900 MHz NMR spectrometer equipped with a 5 mm carbon-sensitive inverse cryoprobe, it was possible to achieve a substantial increase in SNR (46-fold) as compared with a conventional room temperature 400 MHz instrument. Switching from standard 5 mm NMR tube to 3 mm Shigemi microcell assembly typically improved SNR by threefold on either 600 or 900 MHz cryoplatform. A quantitation method that relies on a calibrated residual protonated NMR solvent signal as internal standard was developed using the same hardware setup and restricted sample volume tubes. Linearity of the method spans over 3 orders of magnitude, from low microgram to milligram quantities. We successfully applied this method to quantify a low micrgram sample of paclitaxel, verified by a UV/VIS quantitation measurement.
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Affiliation(s)
- Aleksej Krunić
- Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, University of Illinois at Chicago, Chicago, IL, 60612, USA
| | - Jimmy Orjala
- Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, University of Illinois at Chicago, Chicago, IL, 60612, USA
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Wang X, Isley Iii WC, Salido SI, Sun Z, Song L, Tsai KH, Cramer CJ, Dorn HC. Optimization and prediction of the electron-nuclear dipolar and scalar interaction in 1H and 13C liquid state dynamic nuclear polarization. Chem Sci 2015; 6:6482-6495. [PMID: 30090267 PMCID: PMC6054052 DOI: 10.1039/c5sc02499d] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Accepted: 07/25/2015] [Indexed: 12/19/2022] Open
Abstract
During the last 10-15 years, dynamic nuclear polarization (DNP) has evolved as a powerful tool for hyperpolarization of NMR and MRI nuclides. However, it is not as well appreciated that solution-state dynamic nuclear polarization is a powerful approach to study intermolecular interactions in solution. For solutions and fluids, the 1H nuclide is usually dominated by an Overhauser dipolar enhancement and can be significantly increased by decreasing the correlation time (τc) of the substrate/nitroxide interaction by utilizing supercritical fluids (SF CO2). For molecules containing the ubiquitous 13C nuclide, the Overhauser enhancement is usually a profile of both scalar and dipolar interactions. For carbon atoms without an attached hydrogen, a dipolar enhancement usually dominates as we illustrate for sp2 hybridized carbons in the fullerenes, C60 and C70. However, the scalar interaction is dependent on a Fermi contact interaction which does not have the magnetic field dependence inherent in the dipolar interaction. For a comprehensive range of molecular systems we show that molecules that exhibit weakly acidic complexation interaction(s) with nitroxides provide corresponding large scalar enhancements. For the first time, we report that sp hybridized (H-C) alkyne systems, for example, the phenylacetylene-nitroxide system exhibit very large scalar dominated enhancements. Finally, we demonstrate for a wide range of molecular systems that the Fermi contact interaction can be computationally predicted via electron-nuclear hyperfine coupling and correlated with experimental 13C DNP enhancements.
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Affiliation(s)
- X Wang
- Department of Chemistry , Virginia Tech , Blacksburg , Virginia 24061 , USA .
| | - W C Isley Iii
- Department of Chemistry and Minnesota Supercomputing Institute , University of Minnesota , Minneapolis , Minnesota 55455-0431 , USA .
| | - S I Salido
- Department of Chemistry , Virginia Tech , Blacksburg , Virginia 24061 , USA .
| | - Z Sun
- Department of Chemistry , Virginia Tech , Blacksburg , Virginia 24061 , USA .
| | - L Song
- Department of Chemistry , Virginia Tech , Blacksburg , Virginia 24061 , USA .
| | - K H Tsai
- Department of Chemistry , Virginia Tech , Blacksburg , Virginia 24061 , USA .
| | - C J Cramer
- Department of Chemistry and Minnesota Supercomputing Institute , University of Minnesota , Minneapolis , Minnesota 55455-0431 , USA .
| | - H C Dorn
- Department of Chemistry , Virginia Tech , Blacksburg , Virginia 24061 , USA .
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Lingwood MD, Han S. Dynamic nuclear polarization of 13C in aqueous solutions under ambient conditions. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2009; 201:137-145. [PMID: 19783462 DOI: 10.1016/j.jmr.2009.09.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2008] [Revised: 08/01/2009] [Accepted: 09/02/2009] [Indexed: 05/28/2023]
Abstract
The direct enhancement of the (13)C NMR signal of small molecules in solution through Overhauser-mediated dynamic nuclear polarization (DNP) has the potential to enable studies of systems where enhanced signal is needed but the current dissolution DNP approach is not suitable, for instance if the sample does not tolerate a freeze-thaw process or if continuous flow or rapid re-polarization of the molecules is desired. We present systematic studies of the (13)C DNP enhancement of (13)C-labeled small molecules in aqueous solution under ambient conditions, where we observe both dipolar and scalar-mediated enhancement. We show the role of the three-spin effects from enhanced protons on (13)C DNP through DNP experiments with and without broadband (1)H decoupling and by comparing DNP results with H(2)O and D(2)O. We conclude that the efficiency of (13)C Overhauser DNP in small molecules strongly depends on the distance of closest approach between the electron and (13)C nucleus, the presence of a scalar contribution to the coupling factor, and the magnitude of the three-spin effect due to adjacent polarized protons. The enhancement appears to depend less on the translational dynamics of the (13)C-labeled small molecules and radicals.
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Affiliation(s)
- Mark D Lingwood
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, United States
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Comparison of the Molecular Dynamics of C70 in the Solid and Liquid Phases. ADVANCES IN CHEMICAL PHYSICS 2009. [DOI: 10.1155/2009/953198] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A previous study of C70 in deuterated benzenes generated evidence suggesting C70 exhibited unique reorientational behavior depending on its environment. We present a comparison of the dynamic behavior of this fullerene, in the solid and solution phases, to explore any unique features between these two phases. The effective correlation times, τCeff, of C70 in the solid state are 2 to 3 times longer than in solution. In the solid state, a noticeable decrease in all the carbons' correlation times is seen between 293 K to 303 K; suggesting a transition from isotropic to anisotropic reorientational behavior at this temperature change. Although C70 in solution experiences van der Waals type interactions, these interactions are not strong enough to slow the solution-state motion below what is observed in the solid state. All observed differences in the diffusion constants, DX and DZ, in solution are smaller than in the solid state suggesting a lower energy of activation between these two modes of reorientation in the liquid phase. A small-step diffusion “like” condition appears to be thermally generated in the solid phase at 323 K.
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Hughes RM, Mutzenhardt P, Bartolotti L, Rodriguez AA. Experimental and Theoretical Analysis of the Reorientational Dynamics of Fullerene C70 in Various Aromatic Solvents. J Phys Chem A 2008; 112:4186-93. [DOI: 10.1021/jp800027j] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- R. M. Hughes
- Department of Biochemistry, Nanaline Duke Building, Duke University Medical Center, Durham, North Carolina 27710, Faculte des Sciences et Techniques, Laboratoire de Méthodologies RMN, BP 239, Université H. Poincaré, Boulevard des Aigillettes, F54506 Vandoeuvre-lés-Nancy Cedex, France, Department of Chemistry, East Carolina University, Greenville, North Carolina 27858
| | - P. Mutzenhardt
- Department of Biochemistry, Nanaline Duke Building, Duke University Medical Center, Durham, North Carolina 27710, Faculte des Sciences et Techniques, Laboratoire de Méthodologies RMN, BP 239, Université H. Poincaré, Boulevard des Aigillettes, F54506 Vandoeuvre-lés-Nancy Cedex, France, Department of Chemistry, East Carolina University, Greenville, North Carolina 27858
| | - L. Bartolotti
- Department of Biochemistry, Nanaline Duke Building, Duke University Medical Center, Durham, North Carolina 27710, Faculte des Sciences et Techniques, Laboratoire de Méthodologies RMN, BP 239, Université H. Poincaré, Boulevard des Aigillettes, F54506 Vandoeuvre-lés-Nancy Cedex, France, Department of Chemistry, East Carolina University, Greenville, North Carolina 27858
| | - A. A. Rodriguez
- Department of Biochemistry, Nanaline Duke Building, Duke University Medical Center, Durham, North Carolina 27710, Faculte des Sciences et Techniques, Laboratoire de Méthodologies RMN, BP 239, Université H. Poincaré, Boulevard des Aigillettes, F54506 Vandoeuvre-lés-Nancy Cedex, France, Department of Chemistry, East Carolina University, Greenville, North Carolina 27858
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Maly T, Debelouchina GT, Bajaj VS, Hu KN, Joo CG, Mak–Jurkauskas ML, Sirigiri JR, van der Wel PCA, Herzfeld J, Temkin RJ, Griffin RG. Dynamic nuclear polarization at high magnetic fields. J Chem Phys 2008; 128:052211. [PMID: 18266416 PMCID: PMC2770872 DOI: 10.1063/1.2833582] [Citation(s) in RCA: 540] [Impact Index Per Article: 33.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Dynamic nuclear polarization (DNP) is a method that permits NMR signal intensities of solids and liquids to be enhanced significantly, and is therefore potentially an important tool in structural and mechanistic studies of biologically relevant molecules. During a DNP experiment, the large polarization of an exogeneous or endogeneous unpaired electron is transferred to the nuclei of interest (I) by microwave (microw) irradiation of the sample. The maximum theoretical enhancement achievable is given by the gyromagnetic ratios (gamma(e)gamma(l)), being approximately 660 for protons. In the early 1950s, the DNP phenomenon was demonstrated experimentally, and intensively investigated in the following four decades, primarily at low magnetic fields. This review focuses on recent developments in the field of DNP with a special emphasis on work done at high magnetic fields (> or =5 T), the regime where contemporary NMR experiments are performed. After a brief historical survey, we present a review of the classical continuous wave (cw) DNP mechanisms-the Overhauser effect, the solid effect, the cross effect, and thermal mixing. A special section is devoted to the theory of coherent polarization transfer mechanisms, since they are potentially more efficient at high fields than classical polarization schemes. The implementation of DNP at high magnetic fields has required the development and improvement of new and existing instrumentation. Therefore, we also review some recent developments in microw and probe technology, followed by an overview of DNP applications in biological solids and liquids. Finally, we outline some possible areas for future developments.
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Affiliation(s)
- Thorsten Maly
- Department of Chemistry and Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Galia T. Debelouchina
- Department of Chemistry and Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Vikram S. Bajaj
- Department of Chemistry and Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Kan-Nian Hu
- Department of Chemistry and Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Chan-Gyu Joo
- Department of Chemistry and Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | | | - Jagadishwar R. Sirigiri
- Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Patrick C. A. van der Wel
- Department of Chemistry and Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Judith Herzfeld
- Department of Chemistry, Brandels University, Waltham, Massachusetts 02454, USA
| | - Richard J. Temkin
- Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Robert G. Griffin
- Department of Chemistry and Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Hughes R, Mutzenhardt P, Bartolotti L, Rodriguez A. Analysis of the spin-lattice relaxation rate and reorientational dynamics of fullerene C70 in chlorobenzene-d5. J Mol Liq 2005. [DOI: 10.1016/j.molliq.2004.08.035] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Fischer HH, Seiler M, Ertl TS, Eberhardinger U, Bertagnolli H, Schmitt-Willich H, Albert K. Quantification Studies in Continuous-Flow 13C Nuclear Magnetic Resonance Spectroscopy by Use of Immobilized Paramagnetic Relaxation Agents. J Phys Chem B 2003. [DOI: 10.1021/jp021631d] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Holger H. Fischer
- Institut für Organische Chemie, Auf der Morgenstelle 18, 72076 Tübingen, Germany, Institut für Physikalische Chemie, Pfaffenwaldring 55, 70550 Stuttgart, Germany, and Schering AG, 13342 Berlin, Germany
| | - Michael Seiler
- Institut für Organische Chemie, Auf der Morgenstelle 18, 72076 Tübingen, Germany, Institut für Physikalische Chemie, Pfaffenwaldring 55, 70550 Stuttgart, Germany, and Schering AG, 13342 Berlin, Germany
| | - Thomas S. Ertl
- Institut für Organische Chemie, Auf der Morgenstelle 18, 72076 Tübingen, Germany, Institut für Physikalische Chemie, Pfaffenwaldring 55, 70550 Stuttgart, Germany, and Schering AG, 13342 Berlin, Germany
| | - Ulrich Eberhardinger
- Institut für Organische Chemie, Auf der Morgenstelle 18, 72076 Tübingen, Germany, Institut für Physikalische Chemie, Pfaffenwaldring 55, 70550 Stuttgart, Germany, and Schering AG, 13342 Berlin, Germany
| | - Helmut Bertagnolli
- Institut für Organische Chemie, Auf der Morgenstelle 18, 72076 Tübingen, Germany, Institut für Physikalische Chemie, Pfaffenwaldring 55, 70550 Stuttgart, Germany, and Schering AG, 13342 Berlin, Germany
| | - Heribert Schmitt-Willich
- Institut für Organische Chemie, Auf der Morgenstelle 18, 72076 Tübingen, Germany, Institut für Physikalische Chemie, Pfaffenwaldring 55, 70550 Stuttgart, Germany, and Schering AG, 13342 Berlin, Germany
| | - Klaus Albert
- Institut für Organische Chemie, Auf der Morgenstelle 18, 72076 Tübingen, Germany, Institut für Physikalische Chemie, Pfaffenwaldring 55, 70550 Stuttgart, Germany, and Schering AG, 13342 Berlin, Germany
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11
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Lacey ME, Sweedler JV, Larive CK, Pipe AJ, Farrant RD. 1H NMR characterization of the product from single solid-phase resin beads using capillary NMR flow probes. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2001; 153:215-222. [PMID: 11740897 DOI: 10.1006/jmre.2001.2443] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A capillary NMR flow probe was designed to generate high-resolution (1)H NMR spectra at 600 MHz from the cleaved product of individual 160-microm Tentagel combinatorial chemistry beads. By injecting a dissolved sample sandwiched between an immiscible, perfluorinated organic liquid directly into the probe, NMR spectra of the product cleaved from single beads were acquired in just 1 h of spectrometer time without diffusional dilution. Sample handling efficiency on the single bead scale was comparable to that obtained with a bulk sample. Using the relative intensity of the DMSO-d(5)H versus the analyte signals in a fully relaxed CPMG spectrum, the amount of product cleaved from a single bead was determined to be 540+/-170 pmol in one of the samples. Following the NMR data collection, the samples were examined with electrospray ionization mass spectrometry to provide additional structural information. By coupling with microliter-volume fluidic capabilities, the capillary flow probe described here will enable multidimensional characterization of single solid-phase resin products in an online manner.
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Affiliation(s)
- M E Lacey
- Department of Chemistry and Beckman Institute, University of Illinois, Urbana, Illinois 61801, USA
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Lacey ME, Tan ZJ, Webb AG, Sweedle JV. Union of capillary high-performance liquid chromatography and microcoil nuclear magnetic resonance spectroscopy applied to the separation and identification of terpenoids. J Chromatogr A 2001; 922:139-49. [PMID: 11486859 DOI: 10.1016/s0021-9673(01)00912-8] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This paper describes the first coupling of a commercial capillary HPLC system with a diode array spectrophotometric detector and a custom-built nuclear magnetic resonance (NMR) flow microprobe. The eluent from a 3-microm diameter C18 HPLC column is linked to a 500 MHz 1H-NMR microcoil probe with an observe volume of 1.1 microl. The separation and structurally-rich detection of a mixture of terpenoids under both isocratic and gradient solvent elution conditions is presented. The lowest limits of detection yet reported for capillary HPLC on-line measurement (i.e., 37 ng for alpha-pinene) are achieved with this system. The complementary nature of diode array and NMR detection allows stopped-flow data collection from analytes which would otherwise go unnoticed in continuous-flow NMR. Moreover, stopped-flow NMR data is presented for the detection of a trace (sub-nmol) impurity in the sample mixture. Since NMR signals degrade and shift during solvent gradients, flow injection analysis studies are conducted with injected solvent plugs differing in mobile phase composition. The NMR signal degradation accompanying these injections is largely due to the variance in chemical shift with the solvent composition rather than to changes in magnetic susceptibility of the solvent. Characterization of such effects enables the development of improved NMR probes for the coupling of capillary HPLC and NMR.
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Affiliation(s)
- M E Lacey
- Department of Chemistry, University of Illinois at Urbana-Champaign, 61801, USA
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