State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, P. R. China.
J Phys Chem B. 2013 Jan 31;117(4):989-1002. doi: 10.1021/jp310017j. Epub 2013 Jan 15.
Monte Carlo simulations are employed to investigate the adsorption of a flexible linear cationic polyelectrolyte onto a fluid mixed membrane containing neutral (phosphatidyl-choline, PC), multivalent (phosphatidylinositol, PIP(2)), and monovalent (phosphatidylserine, PS) anionic lipids. We systematically study the effect of chain length and charge density of the polyelectrolyte, the solution ionic strength, as well as the membrane compositions on the conformational and interfacial properties of the model system. In particular, we explore (i) the adsorption/desorption limit, (ii) the interfacial structure variations of the adsorbing polyelectrolyte and the lipid membrane, and (iii) the overcharging of the membrane. Polyelectrolyte adsorbs on the membrane when anionic lipid demixing entropy loss and polyelectrolyte flexibility loss due to adsorption are dominated by electrostatic attraction between polyelectrolyte and anionic lipids on the membrane. Polyelectrolytes with longer chain length and higher charge density can adsorb on the membrane with increased anionic lipid density under a higher critical ionic concentration. Below the critical ionic concentration, the adsorption extent increases with the charge density and chain length of the polyelectrolyte and decreases with the ionic strength of the solution. The diffusing anionic lipids prohibit the polyelectrolyte chain from forming too long tails. The adsorbing polyelectrolyte with long chain length and high charge density can overcharge a membrane with low charge density, and conversely, the membrane charge inversion forces the polyelectrolyte chain to form extended loops and tails in the solution.
采用蒙特卡罗模拟方法研究了柔性线性阳离子聚合物在含有中性（磷脂酰胆碱，PC）、多价（磷脂酰肌醇，PIP(2)）和单价（磷脂酰丝氨酸，PS）阴离子脂质的混合流体膜中的吸附。我们系统地研究了聚合物的链长和电荷密度、溶液离子强度以及膜组成对模型体系构象和界面性质的影响。特别地，我们探索了（i）吸附/解吸极限，（ii）吸附聚合物和脂质膜的界面结构变化，以及（iii）膜的过充电。当阴离子脂质的去混合熵损失和由于吸附导致的聚合物灵活性损失被聚合物和膜上的阴离子脂质之间的静电吸引主导时，聚合物就会吸附在膜上。在更高的临界离子浓度下，具有更长链长和更高电荷密度的聚合物可以在更高的阴离子脂质密度下吸附在膜上。在临界离子浓度以下，吸附程度随聚合物的电荷密度和链长的增加而增加，随溶液离子强度的增加而减小。扩散的阴离子脂质阻止聚合物链形成过长的尾部。具有长链长和高电荷密度的吸附聚合物可以使电荷密度低的膜过充电，反之，膜电荷反转迫使聚合物链在溶液中形成扩展的环和尾部。
