Accelerated interleaflet transport of phosphatidylcholine molecules in membranes under deformation.
Accelerated interleaflet transport of phosphatidylcholine molecules in membranes under deformation.
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DOI：
10.1016/s0006-3495(96)79340-2
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发表时间：
1996-09
影响因子：
3.4
通讯作者：
Robert M. Raphael;Richard E. Waugh
中科院分区：
文献类型：
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作者：
Robert M. Raphael;Richard E. Waugh
生物膜是由两个小叶组成的层状结构，能够支持不同的机械应力。小叶之间的应力差异产生在微机械实验中，长细管的脂质（系链）从表面形成的巨大的磷脂囊泡。该实验的最新动态分析预测了瓣叶间侧向滑动导致的瓣叶应力局部差异的松弛。差异应力也可以通过脂质分子的小叶间运输（“触发器”）来松弛。在这份报告中，我们扩展了以前的分析，包括小叶间脂质转运。我们表明，跨膜脂质通量将证明自己作为一个线性增加系链长度随时间的一步减少后，在膜张力。对由硬脂酰-油酰-磷脂酰胆碱加3%二硝基酚连接的二油酰-磷脂酰乙醇胺组成的24种不同囊泡进行多次测量。这些系绳都表现出线性增长阶段的平均值的层间渗透率，CP=0.009 s-1。这相当于机械驱动瓣叶间转运的半衰期约为8分钟。发现该值与化学驱动运输获得的较长时间一致，如果脂质通过双层中的瞬时局部缺陷穿过膜。
Biological membranes are lamellar structures composed of two leaflets capable of supporting different mechanical stresses. Stress differences between leaflets were generated during micromechanical experiments in which long thin tubes of lipid (tethers) were formed from the surfaces of giant phospholipid vesicles. A recent dynamic analysis of this experiment predicts the relaxation of local differences in leaflet stress by lateral slip between the leaflets. Differential stress may also relax by interleaflet transport of lipid molecules ("flip-flop"). In this report, we extend the former analysis to include interleaflet lipid transport. We show that transmembrane lipid flux will evidence itself as a linear increase in tether length with time after a step reduction in membrane tension. Multiple measurements were performed on 24 different vesicles composed of stearoyl-oleoyl-phosphatidylcholine plus 3% dinitrophenol-linked di-oleoyl-phosphatidylethanolamine. These tethers all exhibited a linear phase of growth with a mean value of the rate of interlayer permeation, cp=0.009 s-1. This corresponds to a half-time of approximately 8min for mechanically driven interleaflet transport. This value is found to be consistent with longer times obtained for chemically driven transport if the lipids cross the membrane via transient, localized defects in the bilayer.