耗散粒子动力学研究双层膜线张力与抗弯刚度的关系

利用耗散力粒子动力学模拟方法研究了拉伸状态下双层膜的抗弯刚度与膜孔线张力之间的关系.通过对双层膜在不同投影面积约束下的系统模拟,观察到3个区域:自由振动膜、伸展膜和穿孔膜.由前两个区域的应力张量计算得到的膜的面张力(σΣ)与拟合膜波动性质得到的面张力(σfluc)吻合的很好,除去在两区域的转变点附近σfluc略大于σΣ.当考虑在经典Helfrich弹性膜模型中被忽略的膜厚度时,线张力可以和抗弯刚度用一个简单的模型联系起来.通过对穿孔膜区域的数据进行分析,证明由本模型得到的抗弯刚度与拟合膜波动性质得到的抗弯刚度符合的很好.由此提出一种简便的测量方法,通过计算拉伸膜孔的面张力和统计膜厚度,拟合这个简单模型来测量膜的抗弯刚度.

DISSIPATIVE PARTICLE DYNAMICS SIMULATION ON THE EFFECT OF LINE TENSION ON BENDING RIGIDITY OF BILAYER MEMBRANES

The relationship between line tension and bending rigidity of extended bilayer membrane is studied in this paper.Extensive simulations of bilayer membrane with different projected areas were performed,and three regions have been found,i.e.,freely fluctuating membrane,extended membrane and extended membrane with a pore.Surface tension(σΣ) calculated from stress tensor is in good agreement with that(σfluc) calculated by fitting the membrane fluctuation data in freely fluctuating region and extended region except that at the transition point σfluc is a little higher than σΣ.By introducing a very simple model,line tension of the pore can be calculated from bending rigidity and membrane thickness which is ignored in the classical Helfrich model,on the other hand,bending rigidity can be determined by line tension and membrane thickness.The results in the pore region show that the bending rigidity got from the simple model is in good agreement with the bending rigidity calculated by fitting the membrane fluctuation data in the freely fluctuating region and extended region.A convenient method for measuring the bending rigidity of bilayer membranes is then proposed.