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 C-13 and N-15 NMR spectroscopies. The silk fibroin yields very sharp C-13 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 N-15 CP NMR and N-15 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.