细胞依靠力学传感蛋白感受外部力学环境的变化而产生不同的生物学响应，如细胞分化与迁移等，因此力学传感蛋白在外加拉力作用下的去折叠/折叠过程不仅是个重要的物理问题，也具有重要的生物功能。本项目以重要的肌肉蛋白Titin和细胞骨架蛋白Filamin A为研究对象，利用磁镊单分子操纵技术来研究在生理条件拉力作用下蛋白质折叠与去折叠的性质，这类研究是目前绝大部分实验技术所不能实现的。本项目的主要研究目标和内容包括：（1）研究蛋白质在恒定拉力下的去折叠与折叠过程；（2）通过对蛋白质在临界拉力作用下折叠与去折叠转变的平衡态测量确定蛋白质折叠的自由能曲面；（3）研究蛋白质折叠与去折叠过程对温度、盐浓度等环境因素的依赖关系，确定蛋白质折叠的主要驱动力；（4）探索拉力对蛋白质之间的相互作用的影响。本项目不仅可以阐明蛋白质折叠与去折叠的一般物理规律，也将揭示细胞中的力学传感蛋白行使生物功能的分子机制。

Cells sense their surrounding mechanical environment through force-sensing proteins and generate different response, such as differetiation and migration. The force-dependent folding and unfolding processes of force-sensing proteins are not only an important physical problem, but also have important biological functions. In this proposal, we are going to study the folding and unfolding properties the important muscle protein Titin and cytoskeleton protein Filamin A when they are subject to physiological forces and force-dependent interactions with their binding partners by using magnetic tweezers single molecular manipulation technique. Most other techniques are not able to do similar studies. The main aims and contents of the proposed project include: (1) Measure the force-dependent unfolding rate and folding rate to study the unfolding and folding processes of proteins when they are subjected to physiological forces; (2) Under critical force, the equilibrium folding and unfolding dynamics will be measured over long time to get the free energy landscape of protein folding; (3) The dependence of protein folding/unfolding properties on environment conditions like tempereature and salt concentration will be studied, and main driving force of protein folding will be determined; (4) Explore the force-dependent protein interactions. In addition to disclosing the general properties of protein folding and unfolding, the project will shed light on the functional mechanism of force-sensing proteins in the cell.