Thermal denaturation and structural changes of α-helical proteins in keratins

Franz J. Wortmann, Gabriele Wortmann, Jennifer Marsh, Knut Meinert

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    To gain insight into the thermal stability of intermediate filaments and matrix in the biological composite structure of α-keratins, the thermal denaturation performance of human hair fibers was investigated by Modulated Differential Scanning Calorimetry (MDSC) in the dry and the wet state. Denaturation enthalpy Δ H D in water was found to be independent of heating rate (11.5. J/g) and to be approximately double as high as in the dry state (5.2. J/g). The lower enthalpy (dry) and its dependency on heating rate are attributed to effects of pyrolysis. The stepwise change of reversing heat capacity Δ C p marks the denaturation process as a classic two-stage transition. The increase of Δ C p with heating rate reflects a continuous shift of the nature of the denaturation of the α-helical material, first, into random coil and then towards random β-materials for lower heating rates. Denaturation temperatures follow Arrhenius relationships with heating rate, yielding activation energies of 416. kJ/mol (dry) and 263. kJ/mol (wet), respectively. A decrease of activation energy (wet) for high heating rates supports the hypothesis of systematic changes of the pathway of denaturation. © 2011 Elsevier Inc.
    Original languageEnglish
    Pages (from-to)553-560
    Number of pages7
    JournalJournal of Structural Biology
    Issue number2
    Publication statusPublished - Feb 2012


    • α-Helix
    • Collagen
    • Denaturation
    • DSC
    • Human hair
    • Keratin


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