Interactions of Alkali Metal Chlorides with Phosphatidylcholine Vesicles
Interactions of Alkali Metal Chlorides with Phosphatidylcholine Vesicles
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DOI：
10.1021/la103631y
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发表时间：
2010-12-21
期刊：
影响因子：
3.9
通讯作者：
Dimova, Rumiana
中科院分区：
文献类型：
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作者：
Klasczyk, Benjamin;Knecht, Volker;Dimova, Rumiana
研究了碱金属氯化物与棕榈酰磷脂酰胆碱（POPC）脂质囊泡的相互作用。一套复杂的技术被用来研究生理条件下的结合过程。用等温滴定量热法对碱阳离子与POPC的结合进行了热力学表征。等温线表明，碱基团中所有离子的结合过程都是吸热的，这与人们对微带负电的POPC脂质体与阳离子之间的库仑相互作用的预期相反。这个过程是由熵驱动的，可能与水分子从离子和脂质头基的水合壳中解放出来有关。测得的离子结合的摩尔焓遵循霍夫迈斯特级数。结合常数也被估计，其中锂显示出最强的亲和力POPC膜，其次是其余的离子根据霍夫梅斯特系列。从电泳迁移率和zeta电位测量中观察到，阳离子吸附增加了囊泡的净表面电位。在浓度为100 mM以上，锂离子的吸附导致zeta电位呈微正，其余离子的吸附主要导致膜中和。这是首次研究在生理盐浓度下碱金属氯化物与磷脂酰胆碱膜的结合平衡。
We study the interaction of alkali metal chlorides with lipid vesicles made of palmitoyloleoylphosphatidylcholine (POPC). An elaborate set of techniques is used to investigate the binding process at physiological conditions. The alkali cation binding to POPC is characterized thermodynamically using isothermal titration calorimetry. The isotherms show that for all ions in the alkali group the binding process is endothermic, counterintuitively to what is expected for Coulomb interactions between the slightly negatively charged POPC liposomes and the cations. The process is entropy driven and presumably related to the liberation of water molecules from the hydration shells of the ions and the lipid headgroups. The measured molar enthalpies of the binding of the ions follows the Hofmeister series. The binding constants were also estimated, whereby lithium shows the strongest affinity to POPC membranes, followed by the rest of the ions according to the Hofmeister series. Cation adsorption increases the net surface potential of the vesicles as observed from electrophoretic mobility and zeta potential measurements. While lithium adsorption leads to slightly positive zeta potentials above a concentration of 100 mM, the adsorption of the rest of the ions mainly causes neutralization of the membrane. This is the first study characterizing the binding equilibrium of alkali metal chlorides to phosphatidylcholine membranes at physiological salt concentrations.