作者:Anindita Sengupta、Subrayashastry Aravinda、Narayanaswamy Shamala、K. Muruga Poopathi Raja、Padmanabhan Balaram
DOI:10.1039/b609863k
日期:——
The crystal structures of five model peptides Piv-Pro-Gly-NHMe (1), Piv-Pro-βGly-NHMe (2), Piv-Pro-βGly-OMe (3), Piv-Pro-δAva-OMe (4) and Boc-Pro-γAbu-OH (5) are described (Piv: pivaloyl; NHMe: N-methylamide; βGly: β-glycine; OMe: O-methyl ester; δAva: δ-aminovaleric acid; γAbu: γ-aminobutyric acid). A comparison of the structures of peptides 1 and 2 illustrates the dramatic consequences upon backbone homologation in short sequences. 1 adopts a type II β-turn conformation in the solid state, while in 2, the molecule adopts an open conformation with the β-residue being fully extended. Piv-Pro-βGly-OMe (3), which differs from 2 by replacement of the C-terminal NH group by an O-atom, adopts an almost identical molecular conformation and packing arrangement in the solid state. In peptide 4, the observed conformation resembles that determined for 2 and 3, with the δAva residue being fully extended. In peptide 5, the molecule undergoes a chain reversal, revealing a β-turn mimetic structure stabilized by a CâHâ¯O hydrogen bond.
描述了五种模型肽 Piv-Pro-Gly-NHMe (1)、Piv-Pro-δGly-NHMe (2)、Piv-Pro-δGly-OME (3)、Piv-Pro-δAva-OME (4) 和 Boc-Pro-δ³Abu-OH (5) 的晶体结构(Piv:pivaloyl;NHMe:N-甲基酰胺;δGly:δ-甘氨酸;OMe:O-甲基酯;δ´Ava:´-氨基戊酸;δ³Abu:δ-氨基丁酸):OMe:O-甲基酯;δAva:δ-氨基戊酸;δ³Abu:δ-氨基丁酸)。肽 1 和肽 2 结构的比较说明了短序列中骨干同源后的巨大影响。1 在固态下采用 II 型 β 翻转构象,而在 2 中,分子采用开放构象,β-残基完全伸展。Piv-Pro-βGly-OMe (3) 与 2 不同,其 C 端 NH 基团被一个 O 原子取代,但在固态下分子构象和堆积排列几乎完全相同。在多肽 4 中,观察到的构象类似于为 2 和 3 确定的构象,δAva 残基完全伸展。在肽 5 中,分子发生了链反转,显示出一种由 CâHâ¯O 氢键稳定的δ-匝模仿结构。