Roy R S, Balaram P
Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, India.
J Pept Res. 2004 Mar;63(3):279-89. doi: 10.1111/j.1399-3011.2004.00143.x.
This review briefly surveys the conformational properties of guest omega-amino acid residues when incorporated into host alpha-peptide sequences. The results presented focus primarily on the use of beta- and gamma-residues in alphaomega sequences. The insertion of additional methylene groups into peptide backbones enhances the range of accessible conformations, introducing additional torsional variables. A nomenclature system, which permits ready comparisons between alpha-peptides and hybrid sequences, is defined. Crystal structure determination of hybrid peptides, which adopt helical and beta-hairpin conformations permits the characterization of backbone conformational parameters for beta- and gamma-residues inserted into regular alpha-polypeptide structures. Substituted beta- and gamma-residues are more limited in the range of accessible conformation than their unsubstituted counterparts. The achiral beta,beta-disubstituted gamma-amino acid, gabapentin, is an example of a stereochemically constrained residue in which the torsion angles about the Cbeta-Cgamma (theta1) and Calpha-Cbeta (theta2) bonds are restricted to the gauche conformation. Hybrid sequences permit the design of novel hydrogen bonded rings in peptide structures.
本综述简要概述了客体ω-氨基酸残基掺入主体α-肽序列时的构象性质。所呈现的结果主要聚焦于αω序列中β-和γ-残基的使用。在肽主链中插入额外的亚甲基会增加可及构象的范围，引入额外的扭转变量。定义了一种命名系统，可方便地比较α-肽和杂合序列。对采用螺旋和β-发夹构象的杂合肽进行晶体结构测定，能够表征插入规则α-多肽结构中的β-和γ-残基的主链构象参数。取代的β-和γ-残基在可及构象范围上比未取代的对应物更受限。非手性的β,β-二取代γ-氨基酸加巴喷丁是立体化学受限残基的一个例子，其中围绕Cβ-Cγ（θ1）和Cα-Cβ（θ2）键的扭转角被限制在 gauche 构象。杂合序列允许在肽结构中设计新型氢键环。
