Peptide design. Helix–helix motifs in synthetic sequences
作者:Arindam Banerjee、S. Raghothama、P. Balaram
DOI:10.1039/a700624a
日期:——
Two centrally positioned α-aminoisobutyryl (Aib) residues have been used to stabilize distinct heptapeptide helical segments in the 15-residue synthetic sequence Boc-Met-Ala-Leu-Aib-Val-Ala-Leu-Acp-Val-Ala-Leu-Aib-Val-Ala-Phe-OMe. The helices are connected by the flexible linker õ-aminocaproic acid (Acp). NMR studies in CDCl3 establish helical conformations for both independent segments as evidenced by NHâNH nuclear Overhauser effects (NOEs). The peptide strongly aggregates in CDCl3 with the NH groups of Met(1) and Ala(2) participating in intermolecular hydrogen bonds. In (CD3)2SO two solvated helical segments are supported by NMR results. Solvent dependent breakdown of aggregates on addition of (CD3)2SO to CDCl3 solutions is suggested by analysis of chemical shifts and temperature coefficients of NH protons. The observation of several interhelical NOEs in CDCl3, relatively few NOEs in 10% (CD3)2SOâCDCl3 and their absence in (CD3)2SO provides a means of inferring helix orientations. While an antiparallel arrangement resulting in closed aggregate formation is suggested in CDCl3, a parallel solvated arrangement is favoured in (CD3)2SO.
两个位于中央的α-氨基异丁酸(Aib)残基被用来稳定15残基合成序列Boc-Met-Ala-Leu-Aib-Val-Ala-Leu-Acp-Val-Ala-Leu-Aib-Val-Ala-Phe-OMe中不同的七肽螺旋片段。这些螺旋通过柔性连接子ε-氨基己酸(Acp)连接。在CDCl3中的核磁共振(NMR)研究确立了这两个独立片段的螺旋构象,这是通过NH–NH核Overhauser效应(NOEs)所证实的。在CDCl3中,该肽强烈聚集,其中Met(1)和Ala(2)的NH基团参与了分子间氢键。在(CD3)2SO中,NMR结果支持了两个溶剂化的螺旋片段。通过分析NH质子的化学位移和温度系数,暗示了随着(CD3)2SO加入到CDCl3溶液中,聚集物的溶剂依赖性分解。在CDCl3中观察到多个螺旋间NOEs,而在10% (CD3)2SO–CDCl3中NOEs相对较少,且在(CD3)2SO中完全缺失,这为我们推断螺旋方向提供了依据。虽然在CDCl3中推测形成了闭合的聚集物,并呈现反平行排列,但在(CD3)2SO中则倾向于平行溶剂化排列。