Determination of Accurate 1H Positions of (Ala-Gly)n as a Sequential Peptide Model of Bombyx mori Silk Fibroin before Spinning (Silk I)

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• 作者：Tetsuo Asakura ; Yu Suzuki ; Koji Yazawa ; Akihiro Aoki ; Yusuke Nishiyama ; Katsuyuki Nishimura ; Furitsu Suzuki ; Hironori Kaji
• 刊名：Macromolecules
• 出版年：2013
• 出版时间：October 8, 2013
• 年：2013
• 卷：46
• 期：19
• 页码：8046-8050
• 全文大小：386K
• 年卷期：v.46,no.19(October 8, 2013)
• ISSN：1520-5835

文摘

The accurate ¹H positions of alanine-glycine alternating copolypeptide, (AG)₁₅ with Silk I structure were determined. For the purpose, the geometry optimization was performed starting with the atomic coordinates of the hetero atoms reported previously ( Macromolecules 2005, <em>38em>, 7397鈭?403) and applied only for protons under periodic boundary conditions. The agreement between the calculated and observed chemical shifts of all ¹H,¹³C and ¹⁵N nuclei was excellent, indicating strongly that the determination of all the atomic-coordinate including ¹H nuclei was performed with high accuracy. Here the ¹H chemical shift was obtained by using both 1 mm microcoil MAS NMR probe-head for mass-limited solid-state samples developed by us and ultrahigh field NMR at 920 MHz. The DQ correlations in the ¹H DQMAS NMR spectra were also used to confirm the intra- and intermolecular structures obtained here. The characteristic structure of Silk I which can be easily converted to Silk II by external forces was discussed together with the generation of Silk I structure from the aqueous solution of the silk fibroin.