Structural changes of keratin proteins under high pressure and heat

本工作旨在研究α-角蛋白的微观行为(分子动力学、水-蛋白质相互作用)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α-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转，以及我们从中可以学到什么。关于角蛋白纤维的大部分工作在很久以前就已经完成了。在这里，我们希望利用新的、更灵敏的实验技术，如固态核磁共振与DSC相结合，它有望获得新的见解。纤维性角蛋白是一种耐热蛋白质，能够在130-140°C的温度下保持其性质。它们由嵌入无定形基质中的结晶棒状a-螺旋(中间纤维，IP)组成。基质被认为是动力学地控制α-螺旋的展开，从而控制蛋白质的稳定性。根据公认的模型，非晶态基质的粘度控制着a-螺旋细丝的迁移率。我们小组最近获得的几个结果表明，这个简单模型存在一些缺陷。除了粘度的机械效应外，我们还注意到非晶态基质与晶态中间丝(IPs)的相互作用对类似角蛋白的复合材料的稳定性起着同样的作用。阐明移动性-相互作用竞争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)了解在盒中a-螺旋的情况下如何发生展开，以及如何利用这一点来控制角蛋白的稳定性；ii)跟踪a-螺旋被各种基质包围时发生的展开反应；以及iii)实现角蛋白在水介质中的溶解，并研究溶液及其用途。这些结果对于了解角蛋白蛋白与水的相互作用，以及水、温度和压力在其变性中所起的作用具有重要意义。这些结果不仅对蛋白质科学有用，而且对材料科学也很有用。

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.