β‐Turn Analogues in Model αβ‐Hybrid Peptides: Structural Characterization of Peptides Containing β
<sup>2,2</sup>
Ac
<sub>6</sub>
c and β
<sup>3,3</sup>
Ac
<sub>6</sub>
c Residues
作者:Krishnayan Basuroy、Appavu Rajagopal、Srinivasarao Raghothama、Narayanaswamy Shamala、Padmanabhan Balaram
DOI:10.1002/asia.201200052
日期:2012.7
hydrogen‐bonded turn in the αβ‐hybrid sequence. The observed torsion angles (α(ϕ≈−60°, ψ≈−30°), β(ϕ≈−90°, θ≈60°, ψ≈−90°)) corresponded to a C11 helical turn, which was a backbone‐expanded analogue of the type III β turn in αα sequences. The crystal structure of the peptide Boc‐Phe‐β3,3Ac6c‐NHMe (4) established a C11 hydrogen‐bonded turn with distinctly different backbone torsion angles (α(ϕ≈−60°, ψ≈120°), β(ϕ≈60°
的效果宝石二烷基取代基上的β氨基肽中氨基酸残基的主链构象进行了研究通过使用四个模型肽:将Boc-XXX-β 2,2- AC 6 C(1-氨基甲基环己烷羧酸)-NHMe(XXX = Leu(1),Phe(2); Boc =叔丁氧羰基)和Boc-Xxx- β3,3 Ac 6 c(1-氨基环己烷乙酸)-NHMe(Xxx = Leu(3),Phe(4))。四取代的碳原子限制了关于侧翼单键的立体化学允许的构象的范围。Boc-Leu- β2,2 Ac 6 c-NHMe(1的晶体结构)在αβ杂合序列中建立了一个C 11氢键合的匝。所观察到的扭转角(α(φ ≈60°,ψ听,说: - 30°),β(φ听,说: - 90°,θ ≈60°,ψ听,说: - 90°))对应于C 11螺旋圈,这是α序列中III型β转角的骨架扩展类似物。的肽:Boc-PHE-β的晶体结构3,3 AC 6 C-NHMe(4)建立一个C