Deformation and flow of membrane into tethers extracted from neuronal growth cones
Deformation and flow of membrane into tethers extracted from neuronal growth cones
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DOI：
10.1016/s0006-3495(96)79577-2
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发表时间：
1996-01-01
影响因子：
3.4
通讯作者：
Sheetz, MP
中科院分区：
文献类型：
--
作者：
Hochmuth, RM;Shao, JY;Sheetz, MP
使用激光镊子陷阱产生的力以恒定的速度从神经元生长锥中提取膜系链。热力学分析表明，当系绳延伸时，能量以弯曲和粘附能的形式存储在系绳中，并以“非局部”弯曲的形式存储在细胞体内。假设能量通过三种粘性机制耗散，包括膜流动、形成双层的两个单层之间的滑动以及膜和细胞骨架之间的滑动。分析预测和实验表明系绳力和系绳速度之间存在线性关系。基于系绳半径接近0.2μm和系绳力接近8pN的分析结果和实验测量的计算得出系绳的弯曲模量为2.7×10(-19)N。 m，生长锥中的“表观表面张力”极小，为 0.003 mN/m，其中表观表面张力是远场张力、面内张力和粘附能的总和。用细胞松弛素 B 和 D、乙醇和诺考达唑处理会影响表观表面张力，但不会影响弯曲。 ATP 耗尽对两者都没有影响，而高浓度的 DMSO 则对两者都有影响。在流动条件下，数据显示主要的粘性机制来自膜流过细胞骨架时发生的滑移。 ATP 耗尽和 DMSO 处理会导致有效粘度急剧下降。如果假设膜和细胞骨架之间的滑动发生在水膜中，那么该水膜的平均厚度仅类似于10埃。
Membrane tethers are extracted at constant velocity from neuronal growth cones using a force generated by a laser tweezers trap. A thermodynamic analysis shows that as the tether is extended, energy is stored in the tether as bending and adhesion energies and in the cell body as ''nonlocal'' bending. It is postulated that energy is dissipated by three viscous mechanisms including membrane flow, slip between the two monolayers that form the bilayer, and slip between membrane and cytoskeleton. The analysis predicts and the experiments show a linear relation between tether force and tether velocity. Calculations based on the analytical results and the experimental measurements of a tether radius of similar to 0.2 mu m and a tether force at zero velocity of similar to 8 pN give a bending modulus for the tether of 2.7 x 10(-19) N . m and an extraordinarily small ''apparent surface tension'' in the growth cone of 0.003 mN/m, where the apparent surface tension is the sum of the far-field, in-plane tension and the energy of adhesion. Treatments with cytochalasin B and D, ethanol, and nocodazole affect the apparent surface tension but not bending. ATP depletion affects neither, whereas large concentrations of DMSO affect both. Under conditions of flow, data are presented to show that the dominant viscous mechanism comes from the slip that occurs when the membrane flows over the cytoskeleton. ATP depletion and the treatment with DMSO cause a dramatic drop in the effective viscosity. If it is postulated that the slip between membrane and cytoskeleton occurs in a film of water, then this water film has a mean thickness of only similar to 10 Angstrom.