Intermolecular Packing in B. mori Silk Fibroin: Multinuclear NMR Study of the Model Peptide (Ala-Gly)15 Defines a Heterogeneous Antiparallel Antipolar Mode of Assembly in the Silk II

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• 作者：Tetsuo Asakura ; Takuya Ohata ; Shunsuke Kametani ; Keiko Okushita ; Koji Yazawa ; Yusuke Nishiyama ; Katsuyuki Nishimura ; Akihiro Aoki ; Furitsu Suzuki ; Hironori Kaji ; Anne S. Ulrich ; Mike P. Williamson
• 刊名：Macromolecules
• 出版年：2015
• 出版时间：January 13, 2015
• 年：2015
• 卷：48
• 期：1
• 页码：28-36
• 全文大小：534K
• ISSN：1520-5835

文摘

We have previously suggested that crystalline Bombyx mori silk in silk II form (the silk structure after spinning) is not a simple antiparallel 尾-sheet but is intrinsically heterogeneous. Using the peptide (AG)₁₅, we have obtained the first fully assigned high resolution solid state ¹H NMR spectrum. Distinct heterogeneity was observed, in both ¹H and ¹³C CP/MAS signals. Based on these results, a new model is proposed that contains two different packing arrangements of antiparallel 尾-sheets. The structures were energetically minimized by CASTEP calculation and used to calculate the solid state ¹H, ¹³C, and ¹⁵N NMR chemical shifts using the GIPAW method. This new model was supported by good agreement between the calculated and observed ¹H, ¹³C, and ¹⁵N chemical shifts and relative ¹H鈥?sup>1H proximities obtained from 2D ¹H DQMAS experiments. We conclude that the intermolecular packing of B. mori silk fibroin has been finally resolved.