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首页> 外文期刊>Chemistry: A European journal >Hybrid peptides: Expanding the beta turn in peptide hairpins by the insertion of beta-, gamma-, and delta-residues
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Hybrid peptides: Expanding the beta turn in peptide hairpins by the insertion of beta-, gamma-, and delta-residues

机译：杂合肽：通过插入β，γ和δ残基来扩大肽发夹中的β转角

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摘要

The beta turn segment in designed peptide hairpins has been expanded by the insertion of beta-, gamma- and delta-amino acids at the i+2 position. The model octapeptides Boc-Leu-Phe-Val- (D)Pro-Ac(6)c-Leu-Phe-Val-OMe (1), Boc-Leu-Phe-Val- (D)Pro-beta(3)-Ac(6)c-Leu- Phe-Val-OMe (2), and Boc-Leu-Phe-Val- (D)Pro-Gpn-Leu-Phe-Val-OMe (3) have been shown to adopt (3 hairpin conformations in methanol by the observation of key diagnostic nuclear Overhauser effects. Boc-Leu-Val-Val- (D)Pro-delta-Ava-Leu-Val-Val-OMe (4) adopts a beta hairpin conformation in crystals; this is stabilized by three cross-strand hydrogen bonds as demonstrated by X-ray diffraction. The canonical C-10 turn in an alpha-alpha segment is expanded to C-11, C-12, and C-13 turns in alpha-beta, alpha-gamma, and alpha-delta segments, respectively. The crystal structures of Piv-(L)Pro-(beta(3-)Ac(6)c-NHMe (5) and Boc-Ac(6)c-Gpn-Ac(6)c-OMe (6) reveal intramolecularly hydrogen-bonded C-11 and C-12 conformations, respectively. Computer modeling of octapeptide sequences that contain centrally positioned hybrid-turn segments, by using turn parameters derived from the structures of peptides 5 and 6, establishes the stereochemical acceptability of the beta hairpins in the cases of peptides 2 and 3. Accommodation of omega -amino acids into the turn segments is achieved by the adoption of gauche conformations around the backbone C-C bonds.
机译：通过在i + 2位置插入β-，γ-和δ-氨基酸，可以扩大设计的肽发夹中的β转变节段。模型八肽Boc-Leu-Phe-Val-（D）Pro-Ac（6）c-Leu-Phe-Val-OMe（1），Boc-Leu-Phe-Val-（D）Pro-beta（3） -Ac（6）c-Leu-Phe-Val-OMe（2）和Boc-Leu-Phe-Val-（D）Pro-Gpn-Leu-Phe-Val-OMe（3）已显示采用（通过观察关键的诊断核Overhauser效应，可以发现甲醇中的3个发夹结构，Boc-Leu-Val-Val-（D）Pro-delta-Ava-Leu-Val-Val-OMe（4）在晶体中采用β发夹结构。 X射线衍射表明，这通过三个交叉链氢键得以稳定，α-α片段中的正则C-10转角扩展为α-11的C-11，C-12和C-13转角，α-γ和α-δ片段Piv-（L）Pro-（β（3-）Ac（6）c-NHMe（5）和Boc-Ac（6）c-Gpn的晶体结构-Ac（6）c-OMe（6）分别显示分子内氢键结合的C-11和C-12构象，通过使用源自结构的转弯参数，对包含中心定位的杂化转弯片段的八肽序列进行计算机建模在肽2和3的情况下，肽5和6的s1建立了β发夹的立体化学可接受性。通过在骨架C-C键周围采用薄纱构象来实现将ω-氨基酸容纳在转角区段中。

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