Conformational Characterization of Left-Handed Helices in Poly(尾-benzyl l-aspartate) by 13C Chemical Shift Anisotropy Using Solid-State NMR

详细信息    查看全文

• 作者：Takayuki Kamihara ; Takashi Mizuno ; Akira Shoji ; K. Takegoshi
• 刊名：Macromolecules
• 出版年：2015
• 出版时间：February 10, 2015
• 年：2015
• 卷：48
• 期：3
• 页码：629-636
• 全文大小：438K
• ISSN：1520-5835

文摘

To investigate local structures of left-handed 伪-helix (伪_L) and left-handed 蠅-helix (蠅_L), the principal values (未₁₁, 未₂₂, and 未₃₃) of the ¹³C chemical shift anisotropy (CSA) tensors of the main-chain carbonyl (C鈺怬) carbons in poly(尾-benzyl l-aspartate) were determined by ¹³C switching-angle sample-spinning solid-state NMR. Further, the observed CSA tensor values for 伪_R, 伪_L, and 蠅_L are compared with those obtained by quantum chemical calculation for a model peptide. Although the isotropic chemical shifts of the C鈺怬 carbons in 伪_R, 伪_L, and 蠅_L lie within 卤2 ppm, the 未₂₂ values, whose axis is close to the direction of the hydrogen bond (C鈺怬路路路H鈥揘), are markedly different. In contrast to the relation established for the 未₂₂ values in various 伪_R helices, that is, an increase of the hydrogen-bond length leads to an upfield shift of 未₂₂, the 未₂₂ values for 伪_L and 蠅_L show a downfield shift for the longer hydrogen-bond length.