Duncan Susan L, Larson Ronald G
Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan, USA.
Biophys J. 2008 Apr 15;94(8):2965-86. doi: 10.1529/biophysj.107.114215. Epub 2008 Jan 16.
Although pressure-area isotherms are commonly measured for lipid monolayers, it is not always appreciated how much they can vary depending on experimental factors. Here, we compare experimental and simulated pressure-area isotherms for dipalmitoylphosphatidylcholine (DPPC) at temperatures ranging between 293.15 K and 323.15 K, and explore possible factors influencing the shape and position of the isotherms. Molecular dynamics simulations of DPPC monolayers using both coarse-grained (CG) and atomistic models yield results that are in rough agreement with some of the experimental isotherms, but with a steeper slope in the liquid-condensed region than seen experimentally and shifted to larger areas. The CG lipid model gives predictions that are very close to those of atomistic simulations, while greatly improving computational efficiency. There is much more variation among experimental isotherms than between isotherms obtained from CG simulations and from the most refined simulation available. Both atomistic and CG simulations yield liquid-condensed and liquid-expanded phase area compressibility moduli that are significantly larger than those typically measured experimentally, but compare well with some experimental values obtained under rapid compression.
尽管压力-面积等温线通常是针对脂质单分子层进行测量的，但人们并不总是充分认识到它们会因实验因素而有多大差异。在此，我们比较了在293.15 K至323.15 K温度范围内二棕榈酰磷脂酰胆碱（DPPC）的实验压力-面积等温线和模拟压力-面积等温线，并探讨了影响等温线形状和位置的可能因素。使用粗粒度（CG）模型和原子模型对DPPC单分子层进行的分子动力学模拟得出的结果与一些实验等温线大致相符，但在液-凝区域的斜率比实验观察到的更陡，且向更大面积偏移。CG脂质模型给出的预测结果与原子模拟非常接近，同时大大提高了计算效率。实验等温线之间的差异比从CG模拟和现有最精细模拟获得的等温线之间的差异大得多。原子模拟和CG模拟得出的液-凝相和液-胀相面积压缩模量均明显大于通常实验测量的值，但与在快速压缩下获得的一些实验值比较吻合。
