Morphology and molecular mobility of fibrous hard alpha-keratins by 1H, 13C, and 129Xe NMR.
The morphology and molecular mobility changes of the side chains for hard alpha-keratin due to oxidative and reductive/oxidative treatments for temperatures around the DSC denaturation peak were investigated by (1)H, (13)C, and (129)Xe NMR spectroscopy and (1)H spin diffusion. Proton wide-line spectra were used to obtain the phase composition (rigid, interface, and amorphous fractions) and molecular dynamics of each phase. Proton spin diffusion experiments using a double-quantum filter and initial rate approximation were employed to obtain the dependence of the rigid domain sizes on chemical treatments and denaturation temperatures. A drastic reduction in the rigid domain thickness takes place for the reductive/oxidative treatment. The keratin mobility gradient in the interfacial region at different denaturation temperatures was measured for hard alpha-keratin from (1)H spin diffusion data. (13)C CPMAS spectra were used to provide a detailed examination of the effects of the chemical treatments especially on the disulfide bonds. Thermally polarized (129)Xe spectra suggest the existence of voids in the hard alpha-keratin induced by the reductive and oxidative treatment. The surface of the hard alpha-keratin fiber surface is probed by the laser hyperpolarized (129)Xe. A qualitative model describing the changes induced in hard alpha-keratin protein by chemical transformation was developed and could be correlated with the changes in domain thickness, phase composition, and molecular dynamics.
Baias
Maria
M
DWI an der RWTH Aachen, D-52056 Aachen, Germany.
Demco
Dan E
DE
Istrate
Daniel
D
Popescu
Crisan
C
Blümich
Bernhard
B
Möller
Martin
M
D002152:Calorimetry, Differential Scanning / Q000379:methods; D002244:Carbon / Q000737:chemistry*; D004058:Diffusion; D004220:Disulfides; D006197:Hair; D006801:Humans; D006859:Hydrogen / Q000737:chemistry*; D007633:Keratins / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015233:Models, Statistical; D010100:Oxygen / Q000737:chemistry; D011522:Protons; D013696:Temperature; D014978:Xenon / Q000737:chemistry*
D004220:Disulfides; D011522:Protons; D014978:Xenon; D007633:Keratins; D002244:Carbon; D006859:Hydrogen; D010100:Oxygen