Structure Analysis of Bombyx mori Silk Fibroin Using NMR
Silks from silkworms and spiders continue to attract attention of researchers in many fields, biochemistry, biophysics, analytical chemistry, polymer chemistry, polymer and textile technologies, and biomaterials. Advances in the most famous silk, Bombyx mori silk fibroin (SF) research, provide many new insights into the structure and dynamics of SF. Here, recent NMR analyses about the structures and dynamics of SF were reviewed. The solution structure of SF stored in the middle silk gland of Bombyx mori silkworm was determined using solution NMR in atomic level. This was type II β-turn structure which was close to random coil but existed in the aggregated states. On the other hand, a new structure of the crystalline regions of the SF fiber after spinning (Silk II) was proposed using several solid- state NMR techniques, and well-known Marsh-Pauling structural model for Silk II was denied partially. The conformational change from SF stored in the middle silk gland to SF fiber was monitored by the change in the fraction of several different conformations determined using 13C CP/MAS NMR and discussed in detail on the basis of the primary structure of SF. The hydrations of SF and microscopic interaction with water molecules were also studied by solid state NMR and 2H solution relaxation measurements. Thus, these NMR analyses gave new details relating to the structure and dynamics of SF, which are relevant in light of current interest in the design of man-made new SF and novel SF-based biomaterials.
KeywordsBombyx mori silk fibroin Solution NMR 13C selectively labeling of silk fibroin Silk I and Silk II Type ΙΙ β-turn Antiparallel β-sheet 13C CP/MAS NMR 13C DD/MAS NMR 1H DQMAS NMR 2H T1-T2 Silk fibroin fiber Hydration of silk fibroin Crystalline and noncrystalline region
- 1.Asakura T. In: Miller T, editor. Biotechnology of Silk. Springer; Dordrecht, 2014. Google Scholar
- 21.Asakura T, Demura M, Watanabe Y, Sato K. J Polm Sci Part-B. 1992;30:3–699.Google Scholar
- 23.Rodin VV, Knight DP. Biofizika. 2004;49:800–8.Google Scholar
- 30.Asakura T, Isobe K, Kametani S, Ukpebor OT, Silverstein MC, Boutis GS. Acta Biomaterialia. 2017; in press.Google Scholar
- 37.Fraser B, MacRae TP. Conformations of fibrous proteins and related synthetic polypeptides. New York: Academic Press; 1973.Google Scholar