Department of Biochemistry , University of Alberta , Edmonton , Alberta T6G 2H7 , Canada.
J Phys Chem B. 2019 May 2;123(17):3665-3671. doi: 10.1021/acs.jpcb.9b01741. Epub 2019 Apr 22.
F NMR spectroscopy is a powerful tool for the study of the structures, dynamics, and interactions of proteins bearing cysteine residues chemically modified with a trifluoroacetone group (CYF residue). F NMR relaxation rates for the fluoromethyl group of CYF residues are sensitive to overall rotational tumbling of proteins, fast rotation about the CF methyl axis, and the internal motion of the CYF side-chain. To develop a quantitative understanding of these various motional contributions, we used the model-free approach to extend expressions for F- T NMR relaxation to include side-chain motions for the CYF residue. We complemented the NMR studies with atomic views of methyl rotation and side-chain motions using molecular dynamics simulations. This combined methodology allows for quantitative separation of the contributions of fast pico- to nanosecond dynamics from micro- to millisecond exchange processes to the F line width and highlights the utility of the CYF residue as a sensitive reporter of side-chain environment and dynamics in proteins.
F NMR 光谱学是研究带有三氟乙酰基化学修饰的半胱氨酸残基的蛋白质的结构、动力学和相互作用的有力工具（CYF 残基）。CYF 残基的氟甲基基团的 F NMR 弛豫率对蛋白质的整体旋转翻滚、CF 甲基轴的快速旋转以及 CYF 侧链的内部运动敏感。为了定量理解这些各种运动贡献，我们使用无模型方法将 F-T NMR 弛豫的表达式扩展到包括 CYF 残基的侧链运动。我们使用分子动力学模拟补充了关于甲基旋转和侧链运动的原子视图的 NMR 研究。这种组合方法允许定量分离快速皮秒到纳秒动力学与微秒到毫秒交换过程对 F 线宽的贡献，并突出了 CYF 残基作为蛋白质中侧链环境和动力学的敏感报告者的效用。
