Sugii Taisuke, Takagi Shu, Matsumoto Yoichiro
Department of Mechanical Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
J Chem Phys. 2005 Nov 8;123(18):184714. doi: 10.1063/1.2102900.
In this paper, we investigate the effects of the hydrocarbon chain length of lipid molecules on the permeation process of small molecules through lipid bilayers. We perform molecular-dynamics simulations using three kinds of lipid molecules with different chain length: dilauroylphosphatidylcholine, dimyristoylphosphatidylcholine, and dipalmiltoylphosphatidylcholine. Free-energy profiles of O2, CO, NO, and water molecules are calculated by means of the cavity insertion Widom method and the probability ratio method. We show that the lipid membrane with longer chains has a larger and wider energy barrier. The local diffusion coefficients of water across the bilayers are also calculated by the force autocorrelation function method and the velocity autocorrelation function method. The local diffusion coefficients in the bilayers are not altered significantly by the chain length. We estimate the permeability coefficients of water across the three membranes according to the solubility-diffusion model; we find that the water permeability decreases modestly with increasing chain length of the lipid molecules.
在本文中，我们研究了脂质分子的烃链长度对小分子透过脂质双层渗透过程的影响。我们使用三种具有不同链长的脂质分子进行分子动力学模拟：二月桂酰磷脂酰胆碱、二肉豆蔻酰磷脂酰胆碱和二棕榈酰磷脂酰胆碱。通过空穴插入维登姆方法和概率比方法计算了氧气、一氧化碳、一氧化氮和水分子的自由能分布。我们表明，具有较长链的脂质膜具有更大且更宽的能垒。还通过力自相关函数方法和速度自相关函数方法计算了水在双层膜中的局部扩散系数。双层膜中的局部扩散系数并未因链长而发生显著改变。我们根据溶解度 - 扩散模型估算了水在三种膜上的渗透系数；我们发现，随着脂质分子链长的增加，水的渗透率适度降低。
