Water permeability and mechanical strength of polyunsaturated lipid bilayers
Water permeability and mechanical strength of polyunsaturated lipid bilayers
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DOI：
10.1016/s0006-3495(00)76294-1
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发表时间：
2000-07-01
影响因子：
3.4
通讯作者：
Evans, E
中科院分区：
文献类型：
--
作者：
Olbrich, K;Rawicz, W;Evans, E
用微管抽吸法测定了由多不饱和磷脂酰胆碱PC脂质组成的巨流体双层囊泡的机械强度和透水性。选择了8个合成的二酰基PC，其具有18个碳链，并且不饱和度范围为每个PC分子1个双键（C18：0/1，C18：1/0）至6个双键（diC 18：3）。通过增加移液管加压产生的，在21 ° C下单囊泡裂解的膜张力对于单不饱和PC和二单不饱和PC（18：0/1、18：1/0和diC 18：1）在类似于9至1/0 mN/m的范围内，但是当一个或两个PC链含有两个cia-双键（C18：0/2和diC 18：2）时突然下降至类似于5 mN/m，并且对于diC 18：3甚至更低，类似于3 mN/m。驱动渗透过滤后转移到一个高渗的环境中的单个囊泡，在21摄氏度的水渗透性的表观系数变化不大，在一个范围内从类似的30至40 μ m/s的单和二单不饱和的PC。然而，在链中具有两个或更多个cia-双键的情况下，表观渗透性对于C18：0/2上升到类似于50 μ m/s，然后显著地对于diC 18：2上升到类似于90 μ m/s，并且对于diC 18：3上升到类似于150 μ m/s。发现水渗透性的测量与文献中报道的这些脂质的降低的温度成指数关系。的相关性支持的概念，在热膨胀以上的主要凝胶-液晶转变的双层获得的自由体积的增加是一个主要因素，在水的运输。总之，溶解张力和水渗透性的显著变化表明，当两个或更多个cia-双键与饱和键沿着链交替时，链堆积和内聚相互作用发生重大变化。
Micropipette aspiration was used to test mechanical strength and water permeability of giant-fluid bilayer vesicles composed of polyunsaturated phosphatidylcholine PC lipids. Eight synthetic-diacyl PCs were chosen with 18 carbon chains and degrees of unsaturation that ranged from one double bond (C18:0/1, C18:1/0) to six double bonds per PC molecule (diC18:3). Produced by increasing pipette pressurization, membrane tensions for lysis of single vesicles at 21 degrees C ranged from similar to 9 to 10 mN/m for mono- and dimono-unsaturated PCs (18:0/1, 18:1/0, and diC18:1) but dropped abruptly to similar to 5 mN/m when one or both PC chains contained two cia-double bonds (C18:0/2 and diC18:2) and even lower similar to 3 mN/m for diC18:3. Driven by osmotic filtration following transfer of individual vesicles to a hypertonic environment, the apparent coefficient for water permeability at 21 degrees C varied modestly in a range from similar to 30 to 40 mu m/s for mono- and dimono-unsaturated PCs. However, with two or more cia-double bonds in a chain, the apparent permeability rose to similar to 50 mu m/s for C18:0/2, then strikingly to similar to 90 mu m/s for diC18:2 and similar to 150 mu m/s for diC18:3. The measurements of water permeability were found to scale exponentially with the reduced temperatures reported for these lipids in the literature. The correlation supports the concept that increase in free volume acquired in thermal expansion above the main gel-liquid crystal transition of a bilayer is a major factor in water transport. Taken together, the prominent changes in lysis tension and water permeability indicate that major changes occur in chain packing and cohesive interactions when two or more cia-double bonds alternate with saturated bonds along a chain.