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Updated: Jan 17, 2026

Microfluidic Dry-spinning and Characterization of Regenerated Silk Fibroin Fibers
Published on: September 4, 2017
Structural Analysis of Valine Residues in Silk Fibroin by Solid-State NMR
Misaki Mizushima1, Takashi Mizuno2, Mitsuru Toda2
1Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, 3-9-1, Bunkyo, Fukui-shi, Fukui 910-8507, Japan.
None:
The silk fibroin produced by the silkworm Bombyx mori has a highly repetitive sequence, composed mainly of repeats of GAGAGS or GAGAGA, with some of the A/S residues being replaced by Y or V. Silk fiber is approximately 60% composed of crystalline regions, separated by less structured regions, generally described as amorphous. The crystalline regions are widely thought to be composed mainly of GAGAGS and GAGAGA repeats, and the role of the YV-repeats is not well understood. Because of the heterogeneous nature of silk fiber, it has been difficult to relate structural features to sequence. Here, we use solid-state NMR to study the conformation of valine residues in silk fiber, and in liquid silk before spinning, and we show that the valines have an identical secondary structure distribution to the alanines. This implies that the YV-repeats are part of the crystalline regions and function to demarcate their boundaries, and that the amorphous regions are formed from both AS and YV-repeats.
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