NMR Characterization of Silk Proteins

Structures of Bombyx mori silk fibroin have been studied in solution, in silkworm and in the solid state by means of solution and solid 13 C and 15 N NMR spectroscopies. The silk fibroin yields very sharp 13 C NMR signals in aqueous solution and in silkworm, indicating the fast segmental motion of the main chain in spite of a fairly high molecular weight, 3 x 10 5 . This makes detailed sequential and conformational analyses of the silk fibroin possible. The structure of the silk fiber in the solid state was studied with 15 N CP NMR and 15 N isotope-labeled silk fibroins on the basis of the chemical shift tensors in detail. The torsion angles of the glycine, alanine and tyrosine residues were determined.