Elliott R, Katsov K, Schick M, Szleifer I
Department of Physics, University of Washington, Seattle, WA 98195-1560, USA.
J Chem Phys. 2005 Jan 22;122(4):44904. doi: 10.1063/1.1836753.
A molecular model is proposed of a bilayer consisting of fully saturated dipalmitoylphosphatidylcholine (DPPC) and mono-unsaturated dioleoylphosphatidylcholine (DOPC). The model not only encompasses the constant density within the hydrophobic core of the bilayer, but also the tendency of chain segments to align. It is solved within self-consistent field theory. A model bilayer of DPPC undergoes a main-chain transition to a gel phase, while a bilayer of DOPC does not do so above zero degrees centigrade because of the double bond which disrupts order. We examine structural and thermodynamic properties of these membranes and find our results in reasonable accord with experiment. In particular, order-parameter profiles are in good agreement with NMR experiments. A phase diagram is obtained for mixtures of these lipids in a membrane at zero tension. The system undergoes phase separation below the main-chain transition temperature of the saturated lipid. Extensions to the ternary DPPC, DOPC, and cholesterol system are outlined.
提出了一种由完全饱和的二棕榈酰磷脂酰胆碱（DPPC）和单不饱和的二油酰磷脂酰胆碱（DOPC）组成的双层分子模型。该模型不仅包含双层疏水核心内的恒定密度，还包含链段排列的趋势。它是在自洽场理论中求解的。DPPC的模型双层会发生主链转变为凝胶相，而DOPC双层在零摄氏度以上不会发生这种转变，因为双键会破坏有序性。我们研究了这些膜的结构和热力学性质，发现我们的结果与实验结果合理相符。特别是，序参量分布与核磁共振实验结果吻合良好。得到了零张力下膜中这些脂质混合物的相图。该系统在饱和脂质的主链转变温度以下会发生相分离。概述了向三元DPPC、DOPC和胆固醇系统的扩展。
