State Scientific Center of Russian Federation, Institute for Biomedical Problems, Russian Academy of Sciences, Moscow, Russia.
Biophys J. 2010 Feb 3;98(3):418-24. doi: 10.1016/j.bpj.2009.10.028.
The structural integrity of striated muscle is determined by extra-sarcomere cytoskeleton that includes structures that connect the Z-disks and M-bands of a sarcomere to sarcomeres of neighbor myofibrils or to sarcolemma. Mechanical properties of these structures are not well characterized. The surface structure and transversal stiffness of single fibers from soleus muscle of the rat were studied with atomic force microscopy in liquid. We identified surface regions that correspond to projections of the Z-disks, M-bands, and structures between them. Transversal stiffness of the fibers was measured in each of these three regions. The stiffness was higher in the Z-disk regions, minimal between the Z-disks and the M-bands, and intermediate in the M-band regions. The stiffness increased twofold when relaxed fibers were maximally activated with calcium and threefold when they were transferred to rigor (ATP-free) solution. Transversal stiffness of fibers heavily treated with Triton X-100 was about twice higher than that of the permeabilized ones, however, its regional difference and the dependence on physiological state of the fiber remained the same. The data may be useful for understanding mechanics of muscle fibers when it is subjected to both axial and transversal strain and stress.
横纹肌的结构完整性由肌节外细胞骨架决定，包括将 Z 盘和 M 带连接到肌节相邻肌原纤维或肌膜的结构。这些结构的力学性能尚未很好地描述。我们使用原子力显微镜在液体中研究了来自大鼠比目鱼肌的单纤维的表面结构和横向刚度。我们确定了与 Z 盘、M 带和它们之间的结构相对应的表面区域。在这三个区域中的每一个中都测量了纤维的横向刚度。在 Z 盘区域中的刚度较高，在 Z 盘和 M 带之间的最小，在 M 带区域中的中等。当用钙使松弛的纤维最大激活时，刚度增加两倍，当将它们转移到严格（无 ATP）溶液时，刚度增加三倍。用 Triton X-100 处理过的纤维的横向刚度大约比通透化的纤维高两倍，但是，其区域差异和对纤维生理状态的依赖性仍然相同。当肌肉纤维同时受到轴向和横向应变和应力时，这些数据可能有助于理解肌肉纤维的力学。
