Dynamic features of side chains in tyrosine and serine residues of some polypeptides and fibroins in the solid as studied by high-resolution solid-state carbon-13 NMR spectroscopy

13 C NMR peaks of Tyr residues were identified, except for the peak of Cβ, by comparing 13 C NMR peaks of the B, mori fibroin with those of the crystalline fraction whose Tyr residue is reduced to less than 2%. The phenolic ring of Tyr residues undergoes a flip-flop motion with a rate constant of >10 2 s −1 . The aromatic side chains of (Tyr) n and (Phe) n , undergo rotational diffusion with a correlation time on the order of 10 −8 s