Magnesium-induced lipid bilayer microdomain reorganizations: implications for membrane fusion.
Magnesium-induced lipid bilayer microdomain reorganizations: implications for membrane fusion.
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DOI：
10.1021/jp9011944
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发表时间：
2009-07-23
期刊：
影响因子：
--
通讯作者：
Levin IW
中科院分区：
文献类型：
--
作者：
Schultz ZD;Pazos IM;McNeil-Watson FK;Lewis EN;Levin IW
二棕榈酰磷脂酰胆碱（DPPC）和二棕榈酰磷脂酰丝氨酸（DPPS）之间的相互作用，结合作为二元脂质双层组件和单独的影响下，二价Mg 2+，膜双层融合剂，报告。的脂酰基链亚甲基对称拉伸模式的红外振动光谱分析表明，两个磷脂组分的聚集体存在的域不均匀地分布在整个二元双层系统。在Mg 2+的存在下，DPPS通过相变温度保持有序的正交晶系亚胞凝胶相结构，而DPPC组分仅相对于凝胶到液晶相变受到最小的扰动。Mg 2+的加入诱导脂质结构域的重组，其中凝胶相酰基链平面从六方构型朝向三斜晶系平行链亚细胞重排。在低温下的酰基链亚甲基变形模式的检查允许DPPS微区尺寸的测定，其在不存在Mg 2+的情况下加入DPPC-d62后尺寸减小。在添加Mg 2+时，在二元混合物中观察到均匀的DPPS畴尺寸。在存在或不存在Mg 2+的情况下，DPPC-d62聚集体保持在微区尺寸不可光谱测量的构型中。在二元体系中DPPC-d62的酰基链亚甲基变形模式的分析表明，氘代脂质的簇分布在整个DPPS基质中。光散射和荧光测量结果表明，Mg 2+诱导的聚集和融合的脂质组件作为一个功能的DPPS的DPPC的比例。的DPPS/DPPC双层内的脂质微结构域的结构重组的背景下，关于脂质双层融合的当前概念进行解释。
Interactions between dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylserine (DPPS), combined both as binary lipid bilayer assemblies and separately, under the influence of divalent Mg2+, a membrane bilayer fusogenic agent, are reported. Infrared vibrational spectroscopic analyses of the lipid acyl chain methylene symmetric stretching modes indicate that aggregates of the two phospholipid components exist as domains heterogeneously distributed throughout the binary bilayer system. In the presence of Mg2+, DPPS maintains an ordered orthorhombic subcell gel phase structure through the phase transition temperature, while the DPPC component is only minimally perturbed with respect to the gel to liquid crystalline phase change. The addition of Mg2+ induces a reorganization of the lipid domains in which the gel phase acyl chain planes rearrange from an hexagonal configuration toward a triclinic, parallel chain subcell. Examination of the acyl chain methylene deformation modes at low temperatures allows a determination of DPPS microdomain sizes, which decrease in size upon the addition of DPPC-d62 in the absence of Mg2+. On adding Mg2+, a uniform DPPS domain size is observed in the binary mixtures. In either the presence or absence of Mg2+, DPPC-d62 aggregates remain in a configuration for which microdomain sizes are not spectroscopically measurable. Analysis of the acyl chain methylene deformation modes for DPPC-d62 in the binary system suggests that clusters of the deuterated lipids are distributed throughout the DPPS matrix. Light scattering and fluorescence measurements indicate that Mg2+ induces both the aggregation and the fusion of the lipid assemblies as a function of the ratio of DPPS to DPPC. The structural reorganizations of the lipid microdomains within the DPPS/DPPC bilayer are interpreted in the context of current concepts regarding lipid bilayer fusion.
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