Müller Thomas J, Müller-Plathe Florian
Theoretische Physikalische Chemie, Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Petersenstrasse 20, 64287 Darmstadt, Germany.
Chemphyschem. 2009 Sep 14;10(13):2305-15. doi: 10.1002/cphc.200900156.
The parallel shear viscosity of a dipalmitoylphosphatidylcholine (DPPC) bilayer system is studied by reverse non-equilibrium molecular dynamics simulations (RNEMD) with two different united-atom force fields. The results are related to diffusion coefficients and structural distributions obtained by equilibrium molecular simulations. We investigate technical issues of the algorithm in the bilayer setup, namely, the dependence of the velocity profiles on the imposed flux and the influence of the thermostat on the calculated shear viscosity. We introduce the concept of local shear viscosity and investigate its dependence on the slip velocity of the monolayers and the particle density at the headgroup-water interface and the tail-tail interface. With this we demonstrate that the lipid bilayer is more viscous than the surrounding water phase, and that slip takes place near the headgroup region and in the centre of the bilayer where the alkyl tails meet. We also quantify the apparent increase in viscosity of the water molecules entangled at the water-headgroup interface.
通过使用两种不同的联合原子力场进行反向非平衡分子动力学模拟（RNEMD），研究了二棕榈酰磷脂酰胆碱（DPPC）双层系统的平行剪切粘度。结果与通过平衡分子模拟获得的扩散系数和结构分布相关。我们研究了双层体系中算法的技术问题，即速度分布对施加通量的依赖性以及恒温器对计算得到的剪切粘度的影响。我们引入了局部剪切粘度的概念，并研究了其对单分子层滑移速度以及头基 - 水界面和尾 - 尾界面处粒子密度的依赖性。由此我们证明，脂质双层比周围的水相更具粘性，并且在头基区域附近以及烷基尾部相遇的双层中心发生滑移。我们还量化了在水头基界面处纠缠的水分子粘度的明显增加。
