Department of Physics and Biophysics, University of San Diego, 5998 Alcala Park, San Diego, CA, 92110, USA.
Department of Physics, University of Massachusetts, Amherst, 666N. Pleasant St., Amherst, MA, 01003, USA.
Sci Rep. 2019 Sep 6;9(1):12831. doi: 10.1038/s41598-019-49236-4.
The cytoskeleton precisely tunes its mechanics by altering interactions between semiflexible actin filaments, rigid microtubules, and crosslinking proteins. We use optical tweezers microrheology and confocal microscopy to characterize how varying crosslinking motifs impact the mesoscale mechanics and mobility of actin-microtubule composites. We show that, upon subtle changes in crosslinking patterns, composites can exhibit two distinct classes of force response - primarily elastic versus more viscous. For example, a composite in which actin and microtubules are crosslinked to each other but not to themselves is markedly more elastic than one in which both filaments are independently crosslinked. Notably, this distinction only emerges at mesoscopic scales in response to nonlinear forcing, whereas varying crosslinking motifs have little impact on the microscale mechanics and mobility. Our unexpected scale-dependent results not only inform the physics underlying key cytoskeleton processes and structures, but, more generally, provide valuable perspective to materials engineering endeavors focused on polymer composites.
细胞骨架通过改变半刚性肌动蛋白丝、刚性微管和交联蛋白之间的相互作用来精确调整其力学性质。我们使用光镊微流变学和共聚焦显微镜来描述改变交联模式如何影响肌动蛋白-微管复合材料的介观力学和迁移率。我们表明,在交联模式的细微变化下,复合材料可以表现出两种截然不同的力响应类型——主要是弹性的还是更粘性的。例如,将肌动蛋白和微管彼此交联但不与自身交联的复合物比两者都独立交联的复合物明显更具弹性。值得注意的是,这种区别仅在介观尺度上响应非线性力而出现,而改变交联模式对微尺度力学和迁移率几乎没有影响。我们意想不到的尺度依赖性结果不仅为关键细胞骨架过程和结构的物理基础提供了信息,而且更普遍地为专注于聚合物复合材料的材料工程努力提供了有价值的视角。