Dynamics of silk fibroin studied with NMR spectroscopy

Abstract

This chapter reviews the dynamic nuclear magnetic resonance (NMR) studies of the silk fibroin from silkworms. The chain dynamics of B. mori and S.c. ricini silk fibroins in aqueous solution are studied to determine the relaxation parameters: spin-lattice relaxation time (T1), nuclear Overhauser enhancement (NOE) and line width. 13C NMR observations are also made to study the chain dynamics of silk fibroin stored in the silk gland of living silkworms. The chain dynamics of the B. mori and S.c. ricini silk fibroin fiber are studied with 2H and 13C solid-state NMR. The solid-state NMR spectra of S.c. ricini silk fibroins showed a gradual and monotonic slowdown of the overall molecular motions leading to molecular aggregation. The chain dynamics of silk fibroin absorbed solvent were detected by 1H and 13c solid-state NMR methods, and also by using an NMR imaging method. Electron spin resonance (ESR) approaches are applied to the dynamic studies of tyrosine (Tyr) side-chain in the silk fibroin.