Constant-pressure molecular dynamics investigation of cholesterol effects in a dipalmitoylphosphatidylcholine bilayer.
Constant-pressure molecular dynamics investigation of cholesterol effects in a dipalmitoylphosphatidylcholine bilayer.
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二棕榈酰磷脂酰胆碱双层中胆固醇效应的恒压分子动力学研究。
DOI：
10.1016/s0006-3495(98)77657-x
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发表时间：
1998
影响因子：
3.4
通讯作者：
Tobias,DJ
中科院分区：
文献类型：
--
作者：
Tu,K;Klein,ML;Tobias,DJ
我们报告了一个1.4 ns的恒压分子动力学模拟胆固醇在12.5摩尔%的二棕榈酰磷脂酰胆碱（DPPC）双层在50°C和比较的结果，我们以前的模拟纯DPPC双层。在含胆固醇的双层中，层间距增加了2.5 μ m，与X射线衍射结果一致，而双层厚度仅增加了1 μ m。双层/水界面是更突然的，因为脂质头基更平坦，以填补胆固醇分子留下的空间。这导致较少的补偿由脂质头基的定向水的贡献膜偶极子电位，并可以解释实验观察到的胆固醇的偶极子电位的幅度增加。我们的计算表明，12.5摩尔%的胆固醇并没有显着影响的构象和包装的烃链，并只产生轻微的减少，在空的自由体积。然而，胆固醇有一个显着的影响，在亚纳秒时间尺度的脂质动力学：扩散常数的质量中心的“嘎嘎作响”的运动减少了3倍，和重定向运动的亚甲基基团减慢沿着整个长度的烃链。
We report a 1.4-ns constant-pressure molecular dynamics simulation of cholesterol at 12.5 mol% in a dipalmitoylphosphatidylcholine (DPPC) bilayer at 50°C and compare the results to our previous simulation of a pure DPPC bilayer. The interlamellar spacing was increased by 2.5Å in the cholesterol-containing bilayer, consistent with x-ray diffraction results, whereas the bilayer thickness was increased by only 1Å. The bilayer/water interface was more abrupt because the lipid headgroups lie flatter to fill spaces left by the cholesterol molecules. This leads to less compensation by the lipid headgroups of the oriented water contribution to the membrane dipole potential and could explain the experimentally observed increase in the magnitude of the dipole potential by cholesterol. Our calculations suggested that 12.5 mol% cholesterol does not significantly affect the conformations and packing of the hydrocarbon chains and produces only a slight reduction in the empty free volume. However, cholesterol has a significant influence on the subnanosecond time scale lipid dynamics: the diffusion constant for the center-of-mass "rattling" motion was reduced by a factor of 3, and the reorientational motion of the methylene groups was slowed along the entire length of the hydrocarbon chains.