Ergosterol in POPC membranes: Physical properties and comparison with structurally similar sterols
Ergosterol in POPC membranes: Physical properties and comparison with structurally similar sterols
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DOI：
10.1529/biophysj.106.097345
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发表时间：
2007-03-01
影响因子：
3.4
通讯作者：
Thewalt, Jenifer
中科院分区：
文献类型：
--
作者：
Hsueh, Ya-Wei;Chen, Mei-Ting;Thewalt, Jenifer
用氢核磁共振(H-2核磁共振)和囊泡挤出法研究了1-palmitoyl-2-oleoyi-sn-glycero-3-phosphocholine/麦角甾醇双层膜的液晶相物理性质。在~2H核磁共振实验中，对POPC的sn-1链进行了过氢化，并将光谱作为麦角甾醇浓度和温度的函数。液晶光谱分析提供了明确的证据，表明在很宽的温度范围内(从-2到至少31℃)，具有不同平均链构象的两种类型的液晶区共存于80：20和75：25 POPC/麦角甾醇膜中。通过核磁共振谱一阶矩M测量，将麦角甾醇加入到浓度为25mol%的POPC-d(31)中，增加了POPC-d(31)的有序性，并增加了从囊泡挤出获得的膜裂解张力。进一步添加麦角甾醇对链序和裂解张力均无影响。这一行为与胆固醇对POPC膜的影响形成了鲜明的对比：POPC/胆固醇膜的链序与至少40mol%的甾醇浓度呈线性关系。为了进一步研究，我们比较了几种POPC/甾醇膜在25℃下对甾醇结构、核磁共振谱和裂解张力的依赖关系。对于本研究中研究的所有POPC/甾醇膜，我们观察到裂解张力与M-1之间普遍存在线性关系。这表明，酰链有序性的改变直接影响膜的拉伸性能。
The physical properties of 1-palmitoyl-2-oleoyi-sn-glycero-3-phosphocholine (POPC)/ergosterol bilayers in the liquid-crystalline phase were determined using deuterium nuclear magnetic resonance (H-2 NMR) and vesicle extrusion. For the 2 H NMR experiments, the sn-1 chain of POPC was perdeuterated, and spectra were taken as a function of ergosterol concentration and temperature. Analysis of the liquid-crystalline spectra provides clear evidence that two types of liquid-crystalline domains, neither of which is a liquid-ordered phase, having distinct average chain conformations coexist in 80:20 and 75:25 POPC/ergosterol membranes over a wide temperature range (from -2 to at least 31 degrees C). Adding ergosterol to a concentration of 25 mol % increases POPC-d(31) chain ordering as measured by the NMR spectral first moment M, and also increases the membrane lysis tension, obtained from vesicle extrusion. Further addition of ergosterol had no effect on either chain order or lysis tension. This behavior is in marked contrast to the effect of cholesterol on POPC membranes: POPC/cholesterol membranes have a linear dependence of chain order on sterol concentration to at least 40 mol %. To investigate further we compared the dependence on sterol structure and concentration of the NMR spectra and lysis tension for several POPC/sterol membranes at 25 degrees C. For all POPC/sterol membranes investigated in this study, we observed a universal linear relation between lysis tension and M-1. This suggests that changes in acyl chain ordering directly affect the tensile properties of the membrane.