Friction measurement between protein-protein by surface forces apparatus

本研究计划用表面力仪测量蛋白质和蛋白质之间的摩擦。为了完成这个计划，蛋白质必须像单层一样排列在基质上。蛋白样品为兔骨骼肌肌动蛋白和重组肌球蛋白亚片段-1。这些都是在肌肉收缩可能发生摩擦的背景下选择的，这是由作者的摩擦理论支持的。肌动蛋白分子被化学固定并排列在由ECR溅射仪制成的二氧化硅薄膜上形成的马来酰亚胺基团上。利用石英晶体微天平对吸附过程和密度进行了精确测量。另一方面，开发的新型体外运动实验表明，滑动速度随作用力的增加呈指数增长。这一结果表明，滑动速度受肌动蛋白与肌球蛋白之间的粘附力以及ATP水解活性的控制。作者在这里提出了一种可能性，即具有滑动力的平衡力是一种摩擦力，这种摩擦力总是由两个接触体相互摩擦产生的。这种摩擦就是众所周知的阿蒙顿-库仑定律或粘附理论。如果肌动蛋白和肌凝蛋白的界面在滑动运动中表现为固体状，那么即使在溶液中也会自然发生摩擦。在这项研究中，断裂动力学被证明在它们的调解中起作用。弱非共价键在外力作用下的解离动力学最早是由Bell用解离率的现象学模型提出的。Evans和Schulten两组分别在布朗动力学的基础上研究了分子粘附键的断裂动力学。在本工作中，Bell的表达被保存了下来，因为它在各种生物标本中得到了建立。通过断裂动力学或非平衡热力学知识推导出载荷-速度关系。

This study was planned to measure friction between protein and protein by using a surface forces apparatus. To perform the plan, proteins have to be arranged monolayer-like on a substrate. As samples of proteins, actin from rabbit skeletal muscle and recombinant myosin subfragment-1 from Dictyosterium were used. These are selected under a background of the possibility that friction occurs in muscle contraction, which is supported by the author's friction theory. Actin molecules were chemically fixed and arranged on the maleimide groups formed on the silica thin film that was made by an ECR sputtering instrument. The adsorption process and the density were measured precisely by using a quartz crystal microbalance. On the other hand, the developed novel in vitro motility assay showed that sliding speed increases exponentially with increasing the applied force. This result suggests that sliding speed is controlled by the adhesion force between actin and myosin as well as activity of ATP hydrolysis. The author presented, here, a possibility that a balance force with the sliding force is a frictional force that is always produced by rubbing two contact bodies. Such friction is well known as Amontons-Coulomb's law or adhesion theory. If the interface of actin and myosin behaves solid-like in the sliding movement, friction occurs naturally even in solution. In this study, rupture dynamics was shown to play a role of their mediation. The dissociation kinetics of weak noncovalent bonds under external forces was first developed by Bell using a phenomenological model for the dissociation rate. Rupture dynamics of molecular adhesion bonds has been investigated on the basis of Brownian dynamics by independently two groups of Evans and Schulten. In the present work, Bell's expression was saved because it was established in various biological specimens. The load-velocity relation was derived through the knowledge of rupture dynamics or non-equilibrium thermodynamics.