Liu Xiumei, Pollack Gerald H
Department of Bioengineering, University of Washington, Seattle, WA 98195 USA.
Biophys J. 2002 Nov;83(5):2705-15. doi: 10.1016/S0006-3495(02)75280-6.
In this report we characterized the longitudinal elasticity of single actin filaments manipulated by novel silicon-nitride microfabricated levers. Single actin filaments were stretched from zero tension to maximal physiological tension, P(0). The obtained length-tension relation was nonlinear in the low-tension range (0-50 pN) with a resultant strain of approximately 0.4-0.6% and then became linear at moderate to high tensions (approximately 50-230 pN). In this region, the stretching stiffness of a single rhodamine-phalloidin-labeled, 1-microm-long F-actin is 34.5 +/- 3.5 pN/nm. Such a length-tension relation could be characterized by an entropic-enthalpic worm-like chain model, which ascribes most of the energy consumed in the nonlinear portion to overcoming thermal undulations arising from the filament's interaction with surrounding solution and the linear portion to the intrinsic stretching elasticity. By fitting the experimental data with such a worm-like chain model, an estimation of persistence length of approximately 8.75 microm was derived. These results suggest that F-actin is more compliant than previously thought and that thin filament compliance may account for a substantial fraction of the sarcomere's elasticity.
在本报告中，我们表征了由新型氮化硅微加工杠杆操纵的单个肌动蛋白丝的纵向弹性。单个肌动蛋白丝从零张力拉伸至最大生理张力P(0)。在低张力范围（0 - 50 pN）内获得的长度-张力关系是非线性的，应变约为0.4 - 0.6%，然后在中等至高张力（约50 - 230 pN）下变为线性。在该区域，一条1微米长、罗丹明-鬼笔环肽标记的F-肌动蛋白的拉伸刚度为34.5±3.5 pN/nm。这样的长度-张力关系可以用熵-焓蠕虫状链模型来表征，该模型将非线性部分消耗的大部分能量归因于克服细丝与周围溶液相互作用产生的热波动，而线性部分归因于内在的拉伸弹性。通过用这种蠕虫状链模型拟合实验数据，得出持久长度约为8.75微米的估计值。这些结果表明，F-肌动蛋白比之前认为的更具柔韧性，并且细丝的柔韧性可能占肌节弹性的很大一部分。
