Naito Akira, Okushita Keiko, Aoki Akihiro, Asakura Tetsuo
Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan.
J Phys Chem B. 2024 Sep 5;128(35):8459-8468. doi: 10.1021/acs.jpcb.4c03716. Epub 2024 Aug 21.
The structure of silk fibroin (SF) is a subject of significant interest due to its remarkable physical properties; however, its atomic-level structure is still not conclusive. We previously proposed a lamellar stacking structure for the crystalline fraction (Cp) with β-turns occurring every eighth amino acid. In this study, we took the following steps: At first, a model of the chain-folded lamellar stacking structure in antipolar and antiparallel β-sheet layers was constructed. Then, dipolar-assisted rotational resonance solid-state NMR spectra were observed to determine the effective internuclear distance () for the uniformly C-labeled Cp fraction sample. By comparing the experimentally obtained (obs) values with the calculated (calc) values from our structural model, a fairly good correlation between the observed and calculated values of the internuclear distances was obtained with a standard deviation of 0.37 Å. This supports the existence of the chain-folded lamellar stacking structure in the SF fiber. These findings contribute to our understanding of the atomic-level structure of SF and its exceptional properties.
由于丝素蛋白（SF）具有卓越的物理性能，其结构成为了一个备受关注的课题；然而，其原子水平的结构仍未定论。我们之前提出了一种晶体部分（Cp）的层状堆积结构，其中每隔八个氨基酸就会出现β-转角。在本研究中，我们采取了以下步骤：首先，构建了反极和反平行β-折叠层中链折叠层状堆积结构的模型。然后，观察偶极辅助旋转共振固态核磁共振光谱，以确定均匀¹³C标记的Cp部分样品的有效核间距（）。通过将实验获得的（obs）值与我们结构模型计算出的（calc）值进行比较，核间距的观测值与计算值之间获得了相当好的相关性，标准偏差为0.37 Å。这支持了SF纤维中链折叠层状堆积结构的存在。这些发现有助于我们理解SF的原子水平结构及其特殊性能。
