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71.
Mueller GA Kirby TW DeRose EF London RE 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2003,165(2):219-247
A new approach for the isotopic labeling of proteins is proposed that aims to facilitate side chain resonance assignments. Residue-correlated (RC) labeling is achieved by the expression of a protein on a medium containing a mixture of labeled, e.g., [U-13C,15N]amino acids, and NMR silent, [U-2H]amino acids. De novo synthesis of amino acids was suppressed by feedback inhibition by the amino acids in the growth medium and by the addition of beta-chloro-L-alanine, a transaminase inhibitor. Incorporation of these amino acids into synthesized proteins results in a relative diminution of inter-residue NOE interactions and a relative enhancement of intra-residue NOEs. Comparison of the resulting NOE spectra with those obtained from a uniformly labeled sample allows identification of intra-residue NOE peaks. Thus, this approach provides direct information for sidechain assignments in the NOE spectra, which are subsequently used for structural analysis. We have demonstrated the feasibility of this strategy for the 143 amino acid nuclease inhibitor NuiA, both at 35 degrees C, corresponding to a rotational correlation time of 9.5 ns, and at 5 degrees C, corresponding to a rotational correlation time of 22 ns. 相似文献
72.
R. E. London T. E. Walker T. W. Whaley N. A. Matwiyoff 《Magnetic resonance in chemistry : MRC》1977,9(10):598-600
15N n.m.r. spectra of [13C-2, 3-15N2-guanidino]arginine and [13C, 15N2] urea were obtained in D2O and H2O at a variety of pH values both with and without proton decoupling. The effects of the proton exchange rate are readily observable in the proton coupled 15N spectra. When the guanidino group is deprotonated (pK = 12.5), the terminal nitrogens give a single resonance 6.6 ppm downfield of the protonated species, indicating a rapid tautomeric exchange. The observed NH and CN couplings are compared with calculated values, and good agreement is found for 1J(CN) using a Blizzard–Santry type calculation. The ramifications of the proton exchange on 15N n.m.r. spectra of amino acids and peptides are discussed. 相似文献
73.
We present a method of obtaining the apex of the unitarity triangle from measurements of B-->piK decay rates alone. Electroweak penguin amplitudes are included, and are related to tree operators. Discrete ambiguities are removed by comparing solutions with independent experimental data. The theoretical uncertainty in this method is about 10%. 相似文献
74.
荧光寿命的快速傅里叶变换拟合方法 总被引:5,自引:2,他引:5
介绍了一种利用快速傅里叶变换算法对稀土掺杂物质的荧光寿命进行数据拟合的方法。稀土掺杂物质可用来制备多种光学传感器,用于温度、pH值等多种参量测量领域。本方法利用快速傅里叶变换(FFT)结果作为基础,从非零项的相位角的正切值得出被测的荧光寿命,具有速度快、误差小、不受本底干扰等一系列优点。以掺铒光纤为例,通过数字仿真将本方法与其它几种传统的拟合方法进行了比较。快速傅里叶变换方法的测量偏差不到Prony方法的50%,为对数似合(log-fit)方法测量偏差的1/6。另外,快速傅里叶变换方法由于不受本底噪声影响,可以不必在信号处理时去掉本底噪声,因而可以明显缩短测量时间。 相似文献
75.
76.
77.
Franz London 《Mathematische Annalen》1903,57(2):222-230
Ohne Zusammenfassung 相似文献
78.
79.
Scott A. Gabel Linda A. Luck Lawrence G. Werbelow Robert E. London 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1997,128(2)
The13C multiplet structure of
-[1-13C,1-2H]glucose complexed to theEscherichia coliperiplasmic glucose/galactose receptor has been studied as a function of temperature. Asymmetric multiplet patterns observed are shown to arise from dynamic frequency shifts. Multiplet asymmetry contributions resulting from shift anisotropy–dipolar cross correlations were found to be small, with optimal fits of the data corresponding to small, negative values of the correlation factor, χCD-CSA. Additional broadening at higher temperatures most probably results from ligand exchange between free and complexed states. Effects of internal motion are also considered theoretically, and indicate that the order parameter for the bound glucose is ≥0.9. 相似文献
80.
David London 《Israel Journal of Mathematics》1964,2(4):237-244
Matrices with nonnegative elements, which are nonstochastic but have stochastic powers, are considered. These matrices are
characterized in the irreducible case and in the symmetric one.
This paper represents part of a thesis submitted to the Senate of the Technion-Israel Institute of Technology in partial fulfillment
of the requirements for the degree of Doctor of Science. The author wishes to thank Professor B. Schwarz for his guidance
in the preparation of this paper. 相似文献