Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892-0520, USA.
J Biomol NMR. 2020 Dec;74(12):673-680. doi: 10.1007/s10858-020-00349-3. Epub 2020 Oct 1.
Optimized selection of the slow-relaxing components of single-quantum C magnetization in CH methyl groups of proteins using acute (< 90°) angle H radio-frequency pulses, is described. The optimal selection scheme is more relaxation-tolerant and provides sensitivity gains in comparison to the experiment where the undesired (fast-relaxing) components of C magnetization are simply 'filtered-out' and only 90° H pulses are employed for magnetization transfer to and from C nuclei. When applied to methyl C single-quantum Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion experiments for studies of chemical exchange, the selection of the slow-relaxing C transitions results in a significant decrease in intrinsic (exchange-free) transverse spin relaxation rates of all exchanging species. For exchanging systems involving high-molecular-weight species, the lower transverse relaxation rates translate into an increase in the information content of the resulting relaxation dispersion profiles.
优化选择蛋白质中 CH 甲基单量子 C 磁化的慢弛豫成分，使用急性（<90°）角 H 射频脉冲，进行了描述。与实验相比，该最优选择方案具有更高的弛豫容忍度，并提供了灵敏度增益，在该实验中，C 磁化的不需要的（快弛豫）成分只是“过滤掉”，仅使用 90°H 脉冲进行从 C 核到 C 核的磁化转移。当应用于用于研究化学交换的甲基 C 单量子 Carr-Purcell-Meiboom-Gill（CPMG）弛豫色散实验时，对慢弛豫 C 跃迁的选择导致所有交换物种的固有（无交换）横向自旋弛豫率显著降低。对于涉及高分子量物质的交换体系，较低的横向弛豫率转化为产生的弛豫色散谱图的信息量增加。
