Monte Carlo study on a complex of cationic polymers and anionic lipid monolayer
Monte Carlo study on a complex of cationic polymers and anionic lipid monolayer
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阳离子聚合物和阴离子脂质单层复合物的蒙特卡罗研究
DOI：
10.1016/j.polymer.2016.10.007
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发表时间：
2016
期刊：
影响因子：
4.6
通讯作者：
Xu Wen-Sheng
中科院分区：
文献类型：
--
作者：
Duan Xiaozheng;Zhang Ran;Zhang Yang;Ding Mingming;Shi Tongfei;An Lijia;Huang Qingrong;Xu Wen-Sheng
We develop a coarse-grained Monte Carlo model for the anchoring of cationic polymers onto a phosphatidyl-choline (PC) lipid monolayer, doped with univalent phosphatidylserine (PS) and tetravalent phosphatidylinositol 4, 5-bisphosphate (PIP2) anionic lipids. Using this model, we extensively explore the effects of important factors on the structural alterations of the polymers/monolayer complex, including the polymer concentration, the polymer ionization fraction and the ionic concentration of the salt solution. We find the substantial disparity in the scaling of the anchoring/dissociation transition for polymers/monolayer complex and polyelectrolyte/surface system, which demonstrates that the mobile anionic monolayer exerts stronger attraction on cationic polymers than uniformly charged surface, thereby illustrating the significant predominance of PIP2lipids in the anchoring procedure. In the polymer anchoring regime, increasing the polymer ionization fraction drastically strengthens the attractions between polymers and the monolayer at low polymer concentrations, which in turn results in the transformation of individual polymer chains from a brush-like structure to a pancake-like structure and leads to the enhancement of PIP2sequestration. Elevating the polymer concentration strengthens the competition of the anchoring between individual polymers, and the fraction of anchored polymers can even saturate at sufficiently high polymer concentrations. At high polymer concentrations, this competition forces both weakly and strongly charged polymers to anchor onto the membrane in the brush-like conformation, thereby sequestering smaller PIP2clusters. The PS lipids cluster around the polymer/PIP2complexes when the amount of tetravalent PIP2lipids is insufficient to neutralize the anchored cationic polymers. We also observe that the monolayer can be overcharged due to the anchoring of polymers at high polymer concentrations. Our work thus approaches an improved understanding of the anchoring processes from a fundamental perspective based on the estimates of the stability and the structural variations of the polymers/monolayer complex with important molecular factors.
