ELASTIC-DEFORMATION AND FAILURE OF LIPID BILAYER-MEMBRANES CONTAINING CHOLESTEROL
ELASTIC-DEFORMATION AND FAILURE OF LIPID BILAYER-MEMBRANES CONTAINING CHOLESTEROL
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DOI：
10.1016/s0006-3495(90)82444-9
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发表时间：
1990-10-01
影响因子：
3.4
通讯作者：
NUNN, RS
中科院分区：
文献类型：
--
作者：
NEEDHAM, D;NUNN, RS
巨双层囊泡由几种脂质和脂质/胆固醇（CHOL）混合物重构：硬脂酰油酰磷脂酰胆碱（SOPC）、牛鞘磷脂（BSM）、二花生四烯酰磷脂酰胆碱（DAPC）、SOPC/CHOL、BSM/CHOL、DAPC/CHOL和提取的红细胞（RBC）脂质与天然胆固醇。单壁囊泡进行了操作微量吸管吸力和几种膜材料的性能进行了测定。测量的性质是弹性面积压缩模量K、临界面积应变α c和拉伸强度τ lys，由此计算破坏能或膜韧性Tf。这些脂质和脂质/胆固醇双层的弹性面积膨胀模量范围为DPC的57达因/厘米至BSM/CHOL的1，734达因/厘米。SPOC/CHOL系列和RBC脂质具有中间值。结果表明，胆固醇的存在是增加双层凝聚力的唯一最有影响力的因素，但仅适用于两条链均饱和或单不饱和或双不饱和的脂质。两条脂链中的多重不饱和抑制了胆固醇在双层中的凝聚作用。对SOPC/CHOL体系进行了较为详细的研究。面积膨胀模量显示随着胆固醇浓度的增加呈非线性增加直至恒定平台，表明双层相中胆固醇的饱和极限为约55mol%CHOL。膜的可压缩性进行了建模的属性平均复合物理论，涉及两个双层组件，即，未复合的脂质和化学计量1/1.22的脂质/胆固醇复合物。该分子复合膜的面积膨胀模量通过组合由其在双层中的面积分数缩放的每个组分的膨胀模量来评估。双层韧性是破坏时储存在双层中的能量，在约40摩尔% CHOL时显示出最大值。发现该击穿能量仅为可用热能的一部分，这意味着许多分子（约50 -100）可能参与形成导致失效的缺陷结构。提取的红细胞脂质与天然胆固醇的面积膨胀模量进行了比较，与最近的测量完整的红细胞膜的可压缩性。天然膜也被建模为一个简单的复合材料，由含有相对不可压缩的跨膜蛋白质的可压缩脂质/胆固醇基质组成。看来，不可压缩的蛋白质与周围的脂质的相互作用赋予增强的压缩性的复合结构。
Giant bilayer vesicles were reconstituted from several lipids and lipid/cholesterol (CHOL) mixtures: stearoyloleoylphosphatidylcholine (SOPC), bovine sphingomyelin (BSM), diarachidonylphosphatidylcholine (DAPC), SOPC/CHOL, BSM/CHOL, DAPC/CHOL, and extracted red blood cell (RBC) lipids with native cholesterol. Single-walled vesicles were manipulated by micropipette suction and several membrane material properties were determined. The properties measured were the elastic area compressibility modulus K, the critical areal strain .alpha.c, and the tensil strength .tau.lys, from which the failure energy or membrane toughness Tf was calculated. The elastic area expansion moduli for these lipid and lipid/cholesterol bilayers ranged from 57 dyn/cm for DPC to 1,734 dyn/cm for BSM/CHOL. The SPOC/CHOL series and RBC lipids had intermediate values. The results indicated that the presence of cholesterol is the single most influential factor in increasing bilayer cohesion, but only for lipids where both chains were saturated, or mono- or diunsaturated. Multiple unsaturation in both lipid chains inhibits the condensing effect of cholesterol in bilayers. The SOPC/CHOL system was studied in more detail. The area expansion modulus showed a nonlinear increase with increasing cholesterol concentration up to a constant plateau, indicating a saturation limit for cholesterol in the bilayer phase of .apprx.55 mol% CHOL. The membrane compressibility was modeled by a property-averaging composite theory involving two bilayer components, namely, uncomplexed lipid and a lipid/cholesterol complex of stoichiometry 1/1.22. The area expansion modulus of this molecular composite membrane was evaluated by a combination of the expansion moduli of each component scaled by their area fractions in the bilayer. Bilayer toughness, which is the energy stored in the bilayer at failure, showed a maximum value at .apprx.40 mol% CHOL. This breakdown energy was found to be only a fraction of the available thermal energy, implying that many molecules (.apprx.50-100) may be involved in forming the defect structure that leads to failure. The area expansion modulus of extracted RBC lipids with native cholesterol was compared with recent measurements of intact RBC membrane compressibility. The natural membrane was also modeled as a simple composite made up of a compressibile lipid/cholesterol matrix containing relatively incompressible transmembrane proteins. It appears that the interaction of incompressibile proteins with surrounding lipid confers enhanced compressibility on the composite structure.