Tugarinov Vitali, Ceccon Alberto, Clore G Marius
Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520, United States.
J Phys Chem B. 2021 Apr 8;125(13):3343-3352. doi: 10.1021/acs.jpcb.1c00989. Epub 2021 Mar 26.
The dynamics of methyl-bearing side chains in proteins were probed by C relaxation measurements of a number of C magnetization modes in selectively CH-labeled methyl groups of proteins. We first show how C magnetization modes in a CH spin-system can be isolated using acute-angle H radio-frequency pulses. The parameters of methyl-axis dynamics, a measure of methyl-axis ordering () and the correlation time of fast local methyl-axis motions (τ), derived from C relaxation in CH groups are compared with their counterparts obtained from C relaxation in CHD methyl isotopomers. We show that in high-molecular-weight proteins, excellent correlations are obtained between the [CHD]-derived values and those extracted from relaxation of the C magnetization of the = 1/2 manifold in CH methyls. In smaller proteins, a certain degree of anticorrelation is observed between the and τ values obtained from C relaxation of the = 1/2 manifold magnetization in CH methyls. These parameters can be partially decorrelated by inclusion in the analysis of relaxation data of the = 3/2 manifold C magnetization.
通过对蛋白质中选择性CH标记甲基的多种碳磁化模式进行碳弛豫测量，探究了蛋白质中含甲基侧链的动力学。我们首先展示了如何使用锐角氢射频脉冲来分离CH自旋系统中的碳磁化模式。将从CH基团的碳弛豫得到的甲基轴动力学参数（一种衡量甲基轴有序性的参数（）和快速局部甲基轴运动的相关时间（τ））与其从CHD甲基异构体中碳弛豫得到的对应参数进行比较。我们表明，在高分子量蛋白质中，从[CHD]得到的值与从CH甲基中 = 1/2流形的碳磁化弛豫提取的值之间具有良好的相关性。在较小的蛋白质中，从CH甲基中 = 1/2流形磁化的碳弛豫得到的和τ值之间观察到一定程度的反相关性。通过在分析中纳入 = 3/2流形碳磁化的弛豫数据，这些参数可以部分去相关。
