Fundamental DSC investigations of alpha-keratinous materials as basis for the interpretation of specific effects of chemical, cosmetic treatments on human hair.

Alpha-keratinous materials can be considered as two-phase, filament/matrix composites, in which partly crystalline, alpha-helical intermediate filaments (if) are embedded in an amorphous matrix of IF-associated proteins (IFAP). Differential Scanning Calorimetry (DSC) of keratins in water was found to be especially suited to analyze various aspects of the thermal stability of these main morphological components. Results and considerations are reviewed, which were gained by applying the principles derived from fundamental investigations to the specific effects of oxidation (bleaching) and reduction (perm-waving). Properties and interactions of the main morphological components of human hair are considered that are specifically related to the various aspects of their thermal stability. The overall view of the results shows that the course of the thermal unfolding of the alpha-helix in the IFs is independent of the chemical history of hair. The matrix properties are the primary factor controlling the kinetics of the onset of the denaturation process in the IF/IFAP-composite.