Dielectric measurement of individual microtubules using the electroorientation method
Dielectric measurement of individual microtubules using the electroorientation method
复制标题
DOI：
10.1529/biophysj.105.071324
复制
发表时间：
2006-05-01
影响因子：
3.4
通讯作者：
Muto, E
中科院分区：
文献类型：
--
作者：
Minoura, I;Muto, E
人们对微管的静电/动态性质知之甚少，因为微管被认为是它们与各种蛋白质，如马达蛋白、微管相关蛋白和微管本身(微管的侧向结合)的静电相互作用的基础。为了测量微管的介电性能，我们开发了一套实验系统，在暗场显微镜下观察微管的电取向。当施加交变电场(0.5-1.9×10(5)V/m，10 kHz-3 MHz)时，由于沿其长轴产生的偶极矩，微管在几秒钟内平行于电场线取向。基于介电椭球模型分析了微管的取向过程，计算了各微管的电导率和介电常数。分析表明，微管具有很高的导电性，这与反离子极化模型是一致的--结合在高负电荷微管上的反离子可以沿着长轴移动，这种迁移性可能是高电导率的根源。我们的实验系统为定量评估微管的聚电解质性质提供了一个有用的工具，从而为未来旨在了解微管与各种蛋白质之间静电相互作用的物理化学机制的研究铺平了道路。
Little is known about the electrostatic/dynamic properties of microtubules, which are considered to underlie their electrostatic interactions with various proteins such as motor proteins, microtubule-associated proteins, and microtubules themselves (lateral association of microtubules). To measure the dielectric properties of microtubules, we developed an experiment system in which the electroorientation of microtubules was observed under a dark-field microscope. Upon application of an alternating electric field (0.5-1.9 x 10(5) V/m, 10 kHz-3 MHz), the microtubules were oriented parallel to the field line in a few seconds because of the dipole moment induced along their long axes. The process of this orientation was analyzed based on a dielectric ellipsoid model, and the conductivity and dielectric constant of each microtubule were calculated. The analyses revealed that the microtubules were highly conductive, which is consistent with the counterion polarization model-counterions bound to highly negatively charged microtubules can move along the long axis, and this mobility might be the origin of the high conductivity. Our experiment system provides a useful tool to quantitatively evaluate the polyelectrolyte nature of microtubules, thus paving the way for future studies aiming to understand the physicochemical mechanism underlying the electrostatic interactions of microtubules with various proteins.