Thermal denaturation of hydrated wool keratin by 1H solid-state NMR.
Thermal denaturation of hydrated keratin in wool was investigated by NMR using 1H wide-line spectra to obtain the phase composition and 1H spin-diffusion experiments using a double-quantum filter to obtain the domain sizes for the wool fibers. The denaturation process detected by DSC takes place for wool fibers in deuterated water in the temperature range 140-144 degreeC. The phase composition measured by 1H wide line NMR spectra reveals a rigid, semirigid and an amorphous phase for temperatures in the range 25-160 degreeC. A dramatic change in the phase composition was detected around 142 degreeC, corresponding to the denaturation temperature. The morphological domain sizes measured by 1H spin-diffusion NMR experiments were obtain from the solutions of the spin-diffusion equations for two-dimensional rectangular and cylindrical morphologies. The keratin mobility gradient in the interfacial region at different denaturation temperatures was measured from the 1H spin-diffusion data. A qualitative model describing the denaturation process of hydrated keratin protein was developed that explains the changes in domain thickness, spin diffusivities, phase composition, and thermodynamic parameters.
Baias
Maria
M
DWI an der RWTH-Aachen University, Pauwelsstrasse 8, D-52056 Aachen, Germany. mbaias@mc.rwth-aachen.de
Demco
Dan E
DE
Popescu
Crisan
C
Fechete
Radu
R
Melian
Claudiu
C
Blümich
Bernhard
B
Möller
Martin
M
D000818:Animals; D002152:Calorimetry, Differential Scanning; D004058:Diffusion; D007633:Keratins / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods / Q000592:standards; D011489:Protein Denaturation; D011522:Protons; D011789:Quantum Theory; D012015:Reference Standards; D012756:Sheep; D013696:Temperature; D014867:Water / Q000737:chemistry*; D014935:Wool / Q000737:chemistry*
D011522:Protons; D014867:Water; D007633:Keratins