C-13 NMR-STUDIES OF KERATIN INTERMEDIATE FILAMENT OF HUMAN HAIR

C-13 n.m.r. spectra of low sulfur fraction in S-(carboxymethyl) kerati ne, (SCMKA), which corresponds to the hard keratin intermediate filame nt (KIF) in human hair were observed in aqueous solution. The spectra were compared with those of SCMKA in 8 M urea and high sulfur fraction in S-(carboxymetyl) keratine, (SCMKB), in aqueous solution. The circu lar dichroism spectrum of SCMKA indicated 40% alpha-helix in the aqueo us solution, and changed to that of random coil in 8 M urea. The SCMKB in aqueous solution also took random coil. The observed peaks in the C-13 n.m.r. spectra of SCMKA in aqueous solution come mainly from the amino acid residues such as Thr, Ser, Pro and Gly in the N- and C-term inal domains with random coil structure. Thus it is suggested that the se domains had high mobility. However, the amino acid residues, Leu, l ie, Gin, Arg and Lys, in the rod domain give essentially no peaks beca use of very restricted motion of the chain with coiled-coil structure. (C) 1997 Elsevier Science Ltd.