Stretching-Induced Conformational Transition of the Crystalline and Noncrystalline Domains of 13C-Labeled Bombyx mori Silk Fibroin Monitored by Solid State NMR

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• 作者：Tetsuo Asakura ; Yuya Sato ; Akihiro Aoki
• 刊名：Macromolecules
• 出版年：2015
• 出版时间：August 25, 2015
• 年：2015
• 卷：48
• 期：16
• 页码：5761-5769
• 全文大小：436K
• ISSN：1520-5835

文摘

It is important to understand the conformational changes of both the crystalline and the noncrystalline domains of Bombyx mori silk fibroin as they are stretched from soluble Silk I to the mature Silk II fiber, to be able to design man-made strong and tough silk fibers. Here, the Ser, Tyr, and Ala C尾 of silk fibroin were labeled by ¹³C to obtain domain-specific structural information, because Ser residues are present predominantly in the crystalline domains, Tyr predominantly in the noncrystalline domains and Ala residues in both domains. The conformational change was monitored by ¹³C CP/MAS NMR using the conformation-dependent ¹³C NMR chemical shift. With increasing stretching ratio, initially there is a change from Silk I* (a repeated type II 尾-turn structure) to 尾-sheet in the longer AGSGAG sequences, followed by shorter AGSGAG sequences, while the noncrystalline domains change gradually from random coil to 尾-sheet during the whole conformational change.