Structural changes of keratin proteins under high pressure and heat

目前的工作旨在研究角蛋白的微观行为（分子动力学，水-蛋白相互作用），及其在介观（结构域大小和形态）和宏观水平上的意义。我们考虑了水、温度和压力对a-角蛋白变性过程的影响，以了解是什么使角蛋白的展开不可逆，以及我们可以从中学到什么。大部分关于角蛋白纤维的研究都是很久以前完成的。在这里，我们希望利用新的和更敏感的实验技术，如固态核磁共振与DSC相结合，这将带来新的见解。纤维角蛋白属于耐热蛋白，能够在高达130-140°C的温度下保持其特性。它们由嵌入在非晶基质中的晶体棒状a-螺旋（中间细丝，IPs）组成。该基质被认为能从动力学上控制a-螺旋的展开，从而控制蛋白质的稳定性。根据公认的模型，非晶基体的粘度控制着a-螺旋丝的迁移率。我们小组最近获得的几个结果表明了这个简单模型的一些缺陷。除了粘度所产生的力学效应外，我们注意到非晶基质与晶体中间细丝（IPs）的相互作用对角蛋白等复合材料的稳定性起着同等的作用。对移动性互动竞争的阐释是本研究的主题之一。更具体地说，该项目旨在研究角蛋白在高压和高温下的行为，以便：i)了解a-螺旋在盒子中是如何展开的，以及如何使用它来控制角蛋白的稳定性；ii)跟踪a-螺旋在被各种基质包围时发生的展开反应；iii)实现角蛋白在水介质中的溶解，并研究溶液及其用途。该结果对了解角蛋白与水的相互作用以及水、温度和压力在其变性中的作用具有重要意义。这些结果不仅对蛋白质科学有用，而且对材料科学也有用。

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.