DPPC双分子层相转变行为的分子动力学模拟研究

Molecular dynamics simulation of phase transition of DPPC bilayer

应用分子动力学模拟技术,对二棕榈酰磷脂酰胆碱双分子层进行退火模拟,从微观水平上深入研究磷脂双层膜的相转变行为.在相变温度附近,磷脂双层膜的物理性质发生突变.在两相各自的温度范围内,凝胶相磷脂双层膜的物理性质随温度变化不明显,但液相呈缓和变化.凝胶相与液相磷脂双层膜的分子构象与其排布方式截然不同：从侧视图来看,前者脂质分子尾链纵向伸展,上下两叶未见交错,叶间隙清晰,后者脂质分子尾链横向弯曲,上下两叶并有交错,叶间隙消失;从俯视图来看,前者脂质分子烃链以极其规律的＂六角边形＂方式排列,而后者脂质分子烃链排列杂乱无章.

The phase behavior of phospholipid bilayer is a research focus in the study of biomembrane.In this paper,molecular dynamics was used to perform the simulated annealing of the bilayer composed of dipalmitoyl phosphatidylcholine（DPPC）.The phase transition of DPPC bilayer was revealed with an intuitive perspective by our study.We found that in the vicinity of the phase transition temperature,the physical properties of the DPPC bilayer had a sudden change.Within liquid phase,there was a mild change for the bilayer properties;however,within gel phase,there was no obvious change for the bilayer properties.What’s more,the gel phase was quite different from the liquid phase for the phospholipid bilayer.From the side view,the phospholipid tails of the former extended longitudinally,and its upper and lower leaves had no stagger,remaining a clear gap;however,the phospholipid tails of the latter had a lateral bending,and its two leaves were crisscross,with gap disappearing.From the top view,the phospholipid hydrocarbon chains kept extremely regular ＂six corners＂arrangement,but these of the latter arranged out of order.