Electrophoresis of individual microtubules in microchannels
Electrophoresis of individual microtubules in microchannels
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DOI：
10.1073/pnas.0608316104
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发表时间：
2007-05-08
影响因子：
11.1
通讯作者：
Dekker, C.
中科院分区：
文献类型：
--
作者：
van den Heuvel, M. G. L.;de Graaff, M. P.;Dekker, C.
我们使用微米大小的流体通道来限制和测量自由悬浮的单个微管的电泳。我们测量了微管的定向速度和通道中的电渗透流动迁移率，以推断生理条件下微管的各向异性电泳迁移率。我们讨论了电泳和纯水动力运动之间的差异及其对解释迁移率测量的影响。我们表明，迁移率各向异性因子为0.83，明显不同于众所周知的圆柱形物体Stokes阻力系数各向异性因子0.5。我们还表明，速度与微管长度无关，这与流体动力运动不同。我们证明了反离子上的电作用力对电泳实验的解释有重要的影响，忽略这一点可能导致有效电荷的数量级低估。通过电泳测量，我们计算出微管的有效表面电荷密度为-36.7 +/- 0.4 mC/m(2)。去除外表面带负电荷的C端后，对枯草菌素消化的微管的电泳测量显示，其迁移率降低了24%，相应地，表面电荷也减少了24%，但各向异性没有变化。
We use micrometer-sized fluidic channels to confine and measure electrophoresis of freely suspended individual microtubules. We measure orientation-dependent velocities of microtubules and the electro-osmotic flow mobility in our channels to infer the anisotropic electrophoretic mobility of microtubules under physiological conditions. We discuss the difference between electrophoresis and purely hydrodynamic motion and its implications for interpreting mobility measurements. We show that the mobility anisotropy is a factor of 0.83, clearly different from the well known anisotropy factor of 0.5 in Stokes drag coefficients for cylindrical objects. We also show that the velocity is independent of microtubule length, which would be different for hydrodynamic motion. We demonstrate that the electric force on the counterions has important consequences for the interpretation of electrophoresis experiments and that ignoring this can lead to an underestimation of the effective charge by orders of magnitude. From the electrophoresis measurements, we calculate an effective surface-charge density of -36.7 +/- 0.4 mC/m(2) for microtubuiles. Electrophoretic measurements of subtilisin-digested microtubules, which have the negatively charged C termini on the outer surface removed, show a 24% decrease in mobility and, correspondingly, in surface charge, but no change in anisotropy.