Structural changes of keratin proteins under high pressure and heat

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The present work aims at investigating the microscopic behaviour (molecular dynamics, interaction water-protein) of a-keratin, and its implications at the mesoscopic (domain size and morphology) and macroscopic levels. We consider the effect of water, temperature and pressure on the denaturation process of a-keratins for understanding what makes the unfolding irreversible in keratins and what can we learn from this. Most of the work on keratin fibres has been performed quite some time ago. Here we wish to take advantage of new and more sensitive experimental techniques like solid-state NMR combined with DSC, which promised new insights. The fibrous keratins are among the thermostable proteins, able to keep their properties at temperatures up to 130-140°C. They are composed of a crystalline rod-like a-helix (intermediate filaments, IPs) embedded in an amorphous matrix. The matrix is considered to control kinetically the unfolding of the a-helix and, therefore, the stability of the protein. According to the accepted model, the viscosity of the amorphous matrix controls the mobility of the a-helix filaments. Several results obtained recently by our group indicate some flaws of this simple model. Beside the mechanical effect exerted by the viscosity, we noticed that the interaction of the amorphous matrix with the crystalline intermediate filaments (IPs) plays an equal role for the stability of the composite like keratin. The elucidation of the mobility-interaction competition is one of the topics of this study. More specifically, the project aims at studying the behaviour of keratins at high pressure and temperature in order to: i) understand how the unfolding occurs in case of a-helix in a box, and how to use this for controlling the stability of the keratin, ii) follow the unfolding reaction of the a-helix occurring when surrounded by various matrices, and iii) achieve at dissolving keratins in aqueous media and study the solution and its usages. The results have implications for learning about the interaction of keratin protein with water, and the role water, temperature and pressure plays in their denaturation. The results are useful not only for protein science, but also for material science.