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31.
13C-only spectroscopy was used to measure multiple residual (13)C-(13)C dipolar couplings (RDCs) in uniformly deuterated and (13)C-labeled proteins. We demonstrate that (13)C-start and (13)C-observe spectra can be routinely used to measure an extensive set of the side-chain residual (13)C-(13)C dipolar couplings upon partial alignment of human ubiquitin in the presence of bacteriophages Pf1. We establish that, among different broadband polarization transfer schemes, the FLOPSY family can be used to exchange magnetization between a J coupled network of spins while largely decoupling dipolar interactions between these spins. An excellent correlation between measured RDCs and the 3D structure of the protein was observed, indicating a potential use of the (13)C-(13)C RDCs in the structure determination of perdeuterated proteins. 相似文献
32.
A number of dimethine and γ-alkoxytetramethine merocyanines derived from 3-ethyl-4-thioxothiazolidin-2-one have been synthesized by the condensation of 5-anilinomethylene-3-ethyl-4-thioxothiazolidin-2-one, obtained by the action of phosphorus pentasulfide on the corresponding 2, 4-dione, with quaternary salts of some 2-methyl- and 2-Β-alkoxypropenyl-substituted heterocyclic bases. The color and photographic properties of the dyes obtained have been studied. 相似文献
33.
Arcadiy V. Krasheninnikov Konstantin E. Kon’kov Leonid A. Openov Vladimir F. Elesin 《Czechoslovak Journal of Physics》1996,46(3):1197-1198
The effect of ion irradiation on the superconducting transition temperatureT c and resistivityρ ab (T) of YBa2Cu3O7-x films with different oxygen content (initial temperatureT c0≈90 K and 60 K) is studied experimentally. The dependenciesT c /T c0 on residual resistivityρ o are obtained in very wide range 0.2<T c /T c0 <1 andρ o μΩ·cm. The critical values ofρ o , corresponding to the vanishing of superconductivity, are found to be an order of magnitude larger then those predicted by theory ford-wave pairing. At 0.5÷0.6<T c /T c0<1 the experimental data are in close agreement with theoretical dependencies, obtained for the anisotropics-wave superconductor within the BCS-framework. 相似文献
34.
A nonperturbative procedure for subtracting singularities caused by finite discontinuities of the field configurations is suggested. This procedure is applied to the Lorentz-covariant quantization of(1+1)-dimensional topological kinks. In the course of this procedure, quantum copies of a classical kink naturally appear. These copies have the same topological charge but have negligibly small sizes and masses because the subtraction procedure eliminates divergences caused by the field differentiations at the discontinuity points. These effects are investigated in detail for those(1+1)-dimensional scalar field models where classical kinks exist.Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 108, No. 2, pp. 212–248, August, 1996. 相似文献
35.
The
p interaction at ultra low energies is considered taking into account the Coulomb interaction. It is shown that Coulomb effects
dramatically modify the usual behaviour of the annihilation cross section. A possibility to extract the scattering length
from experimental data is discussed. 相似文献
36.
The thermally stable, terminal phosphinidene complexes [CpM(CO)2(eta1-PNiPr2)]AlCl4(Cp= Cp, Cp*; M = Fe) and [Cp*M(CO)3(eta1-PNiPr2)]AlCl4 (M = Cr, Mo, W) react with Ph2C=N=N to form terminal P-coordinated eta1-phosphaazine and eta3-diazaphosphaallene ligands, respectively, whereas [CpFe(CO)2(eta1-PNiPr2)]AlCl4 reacts with Me3SiCHN2 affording a terminal phosphorus bound eta1-phosphaalkene complex. 相似文献
37.
Christin Kirst Konstantin Karaghiosoff 《Phosphorus, sulfur, and silicon and the related elements》2020,195(11):918-923
AbstractA novel tertiary phosphine oxide containing two quinaldinyl substituents has been synthesized according to adapted literature procedures. Its coordination properties toward Cu(I) and Ag(I) were investigated and the resulting complexes were analyzed by single crystal X-ray diffraction. Multinuclear complexes are formed, wherein the ligand is bridging across two metal centers. Though for the silver complex, no argentophilic interactions are present. The copper complex was characterized further by multinuclear NMR spectroscopy at variable temperatures. 相似文献
38.
Pavel V. Avramov Konstantin N. Kudin Gustavo E. Scuseria 《Chemical physics letters》2003,370(5-6):597-601
We study the electronic structure of a variety of single wall carbon nanotubes and report density of states obtained with the Perdew–Burke–Ernzerhof (PBE) generalized gradient approximation and hybrid PBE0 approximation of density functional theory using Gaussian orbitals and periodic boundary conditions. PBE gives very good results for metallic tubes but the addition of a portion of exact exchange in the hybrid PBE0 functional worsens the agreement between experiment and theory. On the other hand, the PBE0 hybrid significantly improves the theoretical predictions (compared to PBE) for semiconducting tubes. 相似文献
39.
Konstantin N. Gavrilov Pavel V. Petrovskii AntonS. Safronov Vadim A. Davankov 《Tetrahedron》2005,61(44):10514-10520
Novel P-monodentate aryl phosphite ligands have been synthesised in one step from (R)-BINOL, (R)-H8-BINOL and (R)-H8-3,3′-dibromo-BINOL. With the new aryl phosphites, up to 86% ee was observed in the asymmetric Pd-catalysed amination of 1,3-diphenyl-2-propenyl acetate with sodium diformylamide. In the enantioselective alkylation of 1,3-diphenyl-2-propenyl acetate with dimethyl malonate, up to 97% enantioselectivity was achieved. 相似文献
40.
A general method to enhance the sensitivity of the multidimensional NMR experiments performed at high-polarizing magnetic field via the significant reduction of the longitudinal proton relaxation times is described. The method is based on the use of two vast pools of "thermal bath" 1H spins residing on hydrogens covalently attached to carbon and oxygen atoms in 13C,15N labeled and fully protonated or fractionally deuterated proteins to uniformly enhance longitudinal relaxation of the 1HN spins and concomitantly the sensitivity of multipulse NMR experiments. The proposed longitudinal relaxation optimization is implemented in the 2D [15N,1H]-LTROSY, 2D [15N,1H]-LHSQC and 3D LTROSY-HNCA experiments yielding the factor 2-2.5 increase of the maximal signal-to-noise ratio per unit time at 600 MHz. At 900 MHz, the predicted decrease of the 1HN longitudinal relaxation times can be as large as one order of magnitude, making the proposed method an important tool for protein NMR at high magnetic fields. 相似文献