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- Title
Glycerin-Induced Conformational Changes in Bombyx mori Silk Fibroin Film Monitored by <sub>13</sub>C CP/MAS NMR and <sup>1</sup>H DQMAS NMR.
- Authors
Tetsuo Asakura; Masanori Endo; Misaki Hirayama; Hiroki Arai; Akihiro Aoki; Yugo Tasei
- Abstract
In order to improve the stiff and brittle characteristics of pure Bombyx mori (B. mori) silk fibroin (SF) film in the dry state, glycerin (Glyc) has been used as a plasticizer. However, there have been very limited studies on the structural characterization of the Glyc-blended SF film. In this study, 13C Cross Polarization/Magic Angle Spinning nuclear magnetic resonance (CP/MAS NMR) was used to monitor the conformational changes in the films by changing the Glyc concentration. The presence of only 5 wt % Glyc in the film induced a significant conformational change in SF where Silk I* (repeated type II β-turn and no α-helix) newly appeared. Upon further increase in Glyc concentration, the percentage of Silk I* increased linearly up to 9 wt % Glyc and then tended to be almost constant (30%). This value (30%) was the same as the fraction of Ala residue within the Silk I* form out of all Ala residues of SF present in B. mori mature silkworm. The 1H DQMAS NMR spectra of Glyc-blended SF films confirmed the appearance of Silk I* in the Glyc-blended SF film. A structural model of Glyc-SF complex including the Silk I* form was proposed with the guidance of the Molecular Dynamics (MD) simulation using 1H-1H distance constraints obtained from the 1H Double-Quantum Magic Angle Spinning (DQMAS) NMR spectra.
- Subjects
GLYCERIN; SILKWORMS; NUCLEAR magnetic resonance; MAGIC angle spinning; MOLECULAR dynamics
- Publication
International Journal of Molecular Sciences, 2016, Vol 17, Issue 9, p1517
- ISSN
1661-6596
- Publication type
Article
- DOI
10.3390/ijms17091517