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Insensitive nuclei enhanced by polarization transfer
About: Insensitive nuclei enhanced by polarization transfer is a research topic. Over the lifetime, 482 publications have been published within this topic receiving 18287 citations.
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TL;DR: The method can be used generally for signal enhancement and reduction of measurement time in liquid-state NMR and opens up for a variety of in vitro and in vivo applications of DNP-enhanced NMR.
Abstract: A method for obtaining strongly polarized nuclear spins in solution has
been developed. The method uses low temperature, high magnetic field, and
dynamic nuclear polarization (DNP) to strongly polarize nuclear spins in the
solid state. The solid sample is subsequently dissolved rapidly in a suitable
solvent to create a solution of molecules with hyperpolarized nuclear spins.
The polarization is performed in a DNP polarizer, consisting of a
super-conducting magnet (3.35 T) and a liquid-helium cooled sample space. The
sample is irradiated with microwaves at ≈94 GHz. Subsequent to
polarization, the sample is dissolved by an injection system inside the DNP
magnet. The dissolution process effectively preserves the nuclear
polarization. The resulting hyperpolarized liquid sample can be transferred to
a high-resolution NMR spectrometer, where an enhanced NMR signal can be
acquired, or it may be used as an agent for in vivo imaging or
spectroscopy. In this article we describe the use of the method on aqueous
solutions of [ 13 C]urea. Polarizations of 37% for 13 C and
7.8% for 15 N, respectively, were obtained after the dissolution.
These polarizations correspond to an enhancement of 44,400 for 13 C
and 23,500 for 15 N, respectively, compared with thermal equilibrium
at 9.4 T and room temperature. The method can be used generally for signal
enhancement and reduction of measurement time in liquid-state NMR and opens up
for a variety of in vitro and in vivo applications of
DNP-enhanced NMR.
2,508 citations
1,806 citations
TL;DR: In this article, it was shown that if the electron spin resonance of the conduction electrons is saturated, the nuclei will be polarized to the same degree they would be if their gyromagnetic ratio were that of electron spin.
Abstract: A new method for polarizing nuclei, applicable only to metals, is proposed. It is shown that if the electron spin resonance of the conduction electrons is saturated, the nuclei will be polarized to the same degree they would be if their gyromagnetic ratio were that of the electron spin. This action results from the paramagnetic relaxation processes that occur by means of the hyperfine structure interaction between electron and nuclear spins. A shift of the electron spin resonance due to the same interaction will occur for large amounts of polarization and should provide a direct indication of the degree of polarization.
1,381 citations
TL;DR: Large dynamic nuclear polarization signal enhancements were obtained in the solid-state magic-angle spinning nuclear magnetic resonance (NMR) spectra of arginine and the protein T4 lysozyme in frozen glycerol-water solutions with the use of dynamicnuclear polarization.
Abstract: Large dynamic nuclear polarization signal enhancements (up to a factor of 100) were obtained in the solid-state magic-angle spinning nuclear magnetic resonance (NMR) spectra of arginine and the protein T4 lysozyme in frozen glycerol-water solutions with the use of dynamic nuclear polarization. Polarization was transferred from the unpaired electrons of nitroxide free radicals to nuclear spins through microwave irradiation near the electron paramagnetic resonance frequency. This approach may be a generally applicable signal enhancement scheme for the high-resolution solid-state NMR spectroscopy of biomolecules.
480 citations
TL;DR: In this article, it was demonstrated that the buildup rates of the nuclear Overhauser effect can be measured by two-dimensional NMR spectroscopy with the basic pancreatic trypsin inhibitor.
Abstract: It is demonstrated, by means of experiments with the basic pancreatic trypsin inhibitor, that the buildup rates of the nuclear Overhauser effect can be measured by two-dimensional NMR spectroscopy. Qualitative correlations between the buildup rates of first-order Overhauser effects, which arise from direct dipole-dipole coupling between closely spaced protons, and the proton-proton distances in the protein conformation are established. Second-order Overhauser effects due to spin diffusion by cross-relaxation between more distant protons are also identified. On the basis of these observations, potentialities and limitations of two-dimensional nuclear Overhauser enhancement spectroscopy for studies of the conformation of biological macromolecules are discussed and suggestions made for improved experimental procedures. For quantitative measurements of Overhauser effects, the use of phase-sensitive spectra and of techniques for selective suppression of J cross-peaks in data sets recorded with very short mixing times appears particularly important.
477 citations