期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2004
卷号：101
期号：47
页码：16478-16482
DOI：10.1073/pnas.0407557101
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Conformational studies on the synthetic 11-aa peptide t-butoxycarbonyl (Boc)-Val-Ala-Phe-{alpha}-aminoisobutyric acid (Aib)-(R)-{beta}3-homovaline ({beta}Val)-(S)-{beta}3-homophenylalanine ({beta}Phe)-Aib-Val-Ala-Phe-Aib-methyl ester (OMe) (peptide 1; {beta}Val and {beta}Phe are {beta} amino acids generated by homologation of the corresponding L-residues) establish that insertion of two consecutive {beta} residues into a polypeptide helix can be accomplished without significant structural distortion. Crystal-structure analysis reveals a continuous helical conformation encompassing the segment of residues 2-10 of peptide 1. At the site of insertion of the {beta}{beta} segment, helical hydrogen-bonded rings are expanded. A C15 hydrogen bond for the {alpha}{beta}{beta} segment and two C14 hydrogen bonds for the {alpha}{alpha}{beta} or {beta}{alpha}{alpha} segments have been characterized. The following conformational angles were determined from the crystal structure for the {beta} residues: {beta}Val-5 ({phi} = -126{degrees
关键词：α/β-helix ; C14 hydrogen bond ; C15 hydrogen bond ; αββ segment ; ββα segment
