Optimized selection of the slow-relaxing components of single-quantum ¹³C magnetization in ¹³CH₃ methyl groups of proteins using acute (< 90°) angle ¹H 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 ¹³C magnetization are simply ‘filtered-out’ and only 90° ¹H pulses are employed for magnetization transfer to and from ¹³C nuclei. When applied to methyl ¹³C single-quantum Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion experiments for studies of chemical exchange, the selection of the slow-relaxing ¹³C 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.

描述了使用锐角 (< 90°) ¹ H 射频脉冲在蛋白质的¹³ CH ₃甲基基团中优化选择单量子¹³ C 磁化的缓慢松弛成分。与实验相比，最佳选择方案具有更强的弛豫容忍度并提供灵敏度增益，实验中¹³ C 磁化的不需要（快速弛豫）成分被简单地“过滤掉”，并且仅采用 90° ¹ H 脉冲进行磁化转移往返于¹³ C 原子核。当应用于甲基¹³用于化学交换研究的 C 单量子 Carr-Purcell-Meiboom-Gill (CPMG) 弛豫色散实验，缓慢弛豫¹³ C 跃迁的选择导致本征（无交换）横向自旋弛豫率的显着降低所有交换物种。对于涉及高分子量物质的交换系统，较低的横向弛豫率转化为所得弛豫色散分布的信息含量的增加。