Yang Dan, Li Wei, Qu Jin, Luo Shi-Wei, Wu Yun-Dong
Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
J Am Chem Soc. 2003 Oct 29;125(43):13018-9. doi: 10.1021/ja036136p.
It is known that the seven-membered-ring intramolecular hydrogen bond (gamma-turn) is seldom formed in naturally occurring peptides composed of alpha-amino acids. Here we report a new strategy to induce gamma-turns in short linear peptides. We designed and synthesized several peptides (1-5) containing alternating alpha-l-aminoxy acids and alpha-d-amino acids. 1H NMR studies revealed that the gamma-turn could be initiated by the following N-O turn, an eight-membered-ring intramolecular hydrogen bond induced by an alpha-aminoxy acid. Moreover, NOESY and CD studies suggested peptides 4 and 5 form a novel secondary structure, a mixed 7-8 helix. Theoretical calculations on several di-, tri-, and tetrapeptide models provided strong support to the above conclusions.
众所周知，由α-氨基酸组成的天然肽中很少形成七元环分子内氢键（γ-转角）。在此，我们报道了一种在短线性肽中诱导γ-转角的新策略。我们设计并合成了几种含有交替α-L-氨氧基酸和α-D-氨基酸的肽（1-5）。1H NMR研究表明，γ-转角可由以下N-O转角引发，即由α-氨氧基酸诱导形成的八元环分子内氢键。此外，NOESY和CD研究表明肽4和5形成了一种新型二级结构，即混合7-8螺旋。对几种二肽、三肽和四肽模型的理论计算为上述结论提供了有力支持。
