Direct Evidence for CH···π Interaction Mediated Stabilization of Pro-<i>cis</i>Pro Bond in Peptides with Pro-Pro-Aromatic motifs
作者:Himal K. Ganguly、Barun Majumder、Sarbani Chattopadhyay、Pinak Chakrabarti、Gautam Basu
DOI:10.1021/ja209334v
日期:2012.3.14
weak interactions play subtle but important roles in dictating protein structures, their experimental detection is nontrivial. From NOE experiments we provide direct evidence for the presence of CH···π interaction, operational between the C(α)-H of the first Pro and the aromatic (Aro) side chain of Xaa, in a peptide series with the general sequence Ac-Pro-Pro-Xaa-NH(2). Indirect evidence of CH···π interaction
尽管弱相互作用在决定蛋白质结构方面起着微妙但重要的作用,但它们的实验检测并不简单。从 NOE 实验中,我们为 CH…π 相互作用的存在提供了直接证据,在具有一般序列的肽系列中,第一个 Pro 的 C(α)-H 和 Xaa 的芳族 (Aro) 侧链之间可操作Ac-Pro-Pro-Xaa-NH(2)。CH…π相互作用的间接证据来自Pro(1) C(α)-H化学位移的环电流诱导的高场位移和Xaa侧链(χ1)旋转的限制。这种相互作用的结果是当 Xaa 是芳香族时,Ac-Pro-Pro-Xaa-NH(2) 中 Pro-cisPro 构象异构体的稳定性增强。当 Xaa 为 Tyr、Trp、Phe 时,与 Pro-Pro 部分的反式到顺式转化相关的自由能分别为 0.35、0.59、0.64 和 0.82 kcal/mol,和 His(pH 值为 8.4),分别。相比之下,当 Xaa 为非芳香族时,相应的自由能约为