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1.
Dr. Alexey S. Kiryutin Mikhail S. Panov Dr. Alexandra V. Yurkovskaya Prof. Dr. Konstantin L. Ivanov Prof. Dr. Geoffrey Bodenhausen 《Chemphyschem》2019,20(5):766-772
A study of long-lived spin order in chlorothiophene carboxylates at both high and low magnetic fields is presented. Careful sample preparation (removal of dissolved oxygen in solution, chelating of paramagnetic impurities, reduction of convection) allows one to obtain very long-lived singlet order of the two coupled protons in chlorothiophene derivatives, having lifetimes of about 130 s in D2O and 240 s in deuterated methanol, which are much longer than the T1-relaxation times (18 and 30 s, respectively, at a field =9.4 T). In protonated solvents the relaxation times become shorter, but the lifetime is still substantially longer than . In addition, long-lived coherences are shown to have lifetimes as long as 30 s. Thiophene derivatives can be used as molecular tags to study slow transport, slow dynamics and slow chemical processes, as has been shown in recent years. 相似文献
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Morozova OB Korchak SE Sagdeev RZ Yurkovskaya AV 《The journal of physical chemistry. A》2005,109(45):10459-10466
Using time-resolved chemically induced dynamic nuclear polarization (CIDNP) techniques, we have studied the mechanism of the photoreactions of triplet excited 4-carboxybenzophenone (CBP) with l-methionine (Met) and 3-(methylthio)propylamine (MTPA) in aqueous solution and the details of the formation of CIDNP at pH from 6.7 to 13.6. At a pH below the pKa of the nitrogen atom of Met, the CIDNP is strongly affected by degenerate electron exchange between the S-S cationic radical dimer and the zwitterionic form of Met with the rate constant kex = 3.4 x 10(8) s(-1) providing an exhaustive explanation of the pH dependence of steady-state CIDNP that was previously interpreted as a manifestation of fast interconversion among three different methionine radical species (Goez, M.; Rozwadowski, J. J. Phys. Chem. A 1998, 102, 7945-7953). By analyzing the polarization of different protons formed in geminate recombination as a function of the pH, we obtained the branching ratio between two reaction pathways for oxidative quenching of (T)CBP via electron transfer from the sulfur and nitrogen atoms of Met and MTPA. Nuclear spin-lattice relaxation times were determined in the dimeric cation radical of Met (T1,S = 8.5 micros). In the cyclic radical cation of MTPA with a three-electron two-center S-N bond, the estimated paramagnetic relaxation is comparatively slow for all protons. Fast deprotonation of the primary aminium radical cation of MTPA and Met in strongly basic solution takes place on the submicrosecond time scale leading to efficient formation of CIDNP in the neutral aminyl radical. 相似文献
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Effects of surfactants on the photosensitized production of tyrosine radicals studied by photo-CIDNP
Lopez JJ Carter MA Tsentalovich YP Morozova OB Yurkovskaya AV Hore PJ 《Photochemistry and photobiology》2002,75(1):6-10
The influence of the surfactants sodium dodecyl sulphate, cetyltrimethyl-ammonium bromide and triton X-100 on the photochemically induced dynamic nuclear polarization (CIDNP) of N-acetyl tyrosine has been investigated. Three photosensitizers were used to generate polarization: thionin, eosin Y and flavin mononucleotide. 600 MHz 1H photo-CIDNP experiments, supported by laser flash photolysis transient absorption measurements, indicate that the neutral triton surfactant has no influence on the nuclear polarization, but that the other two, charged, amphiphiles affect the photochemistry in a variety of ways, depending on the surfactant concentration and the identity of the sensitizer. 相似文献
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Russian Chemical Bulletin - In order to model the involvement of histidine radicals in the electron transfer reactions in proteins, we investigated the kinetics of the reduction of hisitidine... 相似文献
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Dr. Alexey S. Kiryutin Dr. Grit Sauer Dr. Daniel Tietze Martin Brodrecht Stephan Knecht Prof. Dr. Alexandra V. Yurkovskaya Prof. Dr. Konstantin L. Ivanov Dr. Olga Avrutina Prof. Dr. Harald Kolmar Prof. Dr. Gerd Buntkowsky 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(16):4025-4030
Two-dimensional NMR spectroscopy is one of the most important spectroscopic tools for the investigation of biological macromolecules. However, due to the low sensitivity of NMR spectroscopy, it takes usually from several minutes to many hours to record such spectra. Here, the possibility of detecting a bioactive derivative of the sunflower trypsin inhibitor-1 (SFTI-1), a tetradecapeptide, by combining parahydrogen-induced polarization (PHIP) and ultrafast 2D NMR spectroscopy is shown. The PHIP activity of the inhibitor was achieved by labeling with O-propargyl-l -tyrosine. In 1D PHIP experiments a signal enhancement of a factor of approximately 1200 compared to standard NMR was found. This enhancement permits measurement of 2D NMR correlation spectra of low-concentrated SFTI-1 in less than 10 seconds, employing ultrafast single-scan 2D NMR detection. As experimental examples PHIP-assisted ultrafast single-scan TOCSY spectra of SFTI-1 are shown. 相似文献
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Olga B. Morozova Robert Kaptein Renad Z. Sagdeev Alexandra V. Yurkovskaya 《Applied magnetic resonance》2013,44(1-2):233-245
Pulsed-field-gradient nuclear magnetic resonance (NMR) combined with time-resolved chemically induced dynamic nuclear polarization (TR-CIDNP) was applied to study the reduction of guanosyl radicals in reactions with the proteins hen egg white lysozyme (HEWL) and bovine α-lactalbumin (BLA) in their native state. Guanosyl radicals were generated photochemically in the reaction of guanosine-5′-monophosphate with photosensitizer, triplet-excited 2,2′-dipyridyl. In this reaction, at pH 5 guanosyl cation radical is formed, which deprotonates to yield the neutral guanosyl radical. To minimize the contribution of the cation radical, phosphate buffer was added, which accelerates the deprotonation of guanosyl cation radical. From model simulations of CIDNP kinetics the rate constants of the reduction were found to be (3.1 ± 0.5) × 107 M?1s?1 for HEWL and (1.6 ± 0.4) × 107 M?1s?1 for BLA. Also, experiments were carried out at the conditions for denatured HEWL, i.e., at 50 °C in the presence of 10 M urea-d4. The rate constant of the reduction of guanosyl radical in this case was (3.6 ± 0.5) × 108 M?1s?1. 相似文献
9.
K. L. Ivanov K. Miesel A. V. Yurkovskaya S. E. Korchak A. S. Kiryutin H. -M. Vieth 《Applied magnetic resonance》2006,30(3-4):513-534
Coherent polarization transfer among groups of dynamically polarized spins is explored and applied to field cycling experiments where spin evolution proceeds at low magnetic field while observation is performed at high field. The case of two nonequivalent spins-1/2 with scalar spin coupling is considered theoretically in detail for the cases of sudden and adiabatic field change. The criterion for efficient polarization transfer is derived theoretically and consistently confirmed experimentally for three photochemical reactions, involving spin systems of increasing complexity that exhibit chemically induced dynamic nuclear polarization: (1) the two polarized protons of the purine base of adenosine monophosphate; (2) four coupled indole protons of tryptophan; and (3) long-range polarization transfer among the aliphatic protons of cycloundecanone. The importance of polarization transfer in other cases with non-equilibrium population of the nuclear spin levels and the possibility of its utilization in field cycling NMR studies are discussed. 相似文献
10.
Kiryutin AS Morozova OB Kuhn LT Yurkovskaya AV Hore PJ 《The journal of physical chemistry. B》2007,111(38):11221-11227
Relative values of the 1H and 13C isotropic hyperfine couplings in the cationic oxidized tryptophan radical TrpH*+ in aqueous solution are determined. The data are obtained from the photo-CIDNP (chemically induced dynamic nuclear polarization) enhancements observed in the microsecond time-resolved NMR spectra of the diamagnetic products of photochemical reactions in which TrpH*+ is a transient intermediate. The method is validated using the tyrosyl neutral radical Tyr*, whose 1H and 13C hyperfine couplings have previously been determined by electron paramagnetic resonance spectroscopy. Good agreement is found with hyperfine coupling constants for TrpH*+ calculated using density functional theory methods but only if water molecules are explicitly included in the calculation. 相似文献