Zhang Z, Sperotto M M, Zuckermann M J, Mouritsen O G
Department of Physics, McGill University, Montréal, Québec, Canada.
Biochim Biophys Acta. 1993 Apr 8;1147(1):154-60. doi: 10.1016/0005-2736(93)90326-u.
A statistical mechanical lattice model is proposed to describe the phase diagram of phospholipid bilayers with small transmembrane proteins or polypeptides. The model is based on the extended Pink-Green-Chapman model (Zhang et al. (1992) Phys. Rev. A 45, 7560-7567) for pure lipid bilayers which undergo a first-order gel-fluid phase transition. The interaction between the lipid bilayer and the protein or polypeptide is modelled using the concept of hydrophobic matching. The phase diagram has been derived by computer-simulation techniques which fully account for thermal density fluctuations and which operate on the level of the free-energy thereby permitting an accurate identification of the phase boundaries. The calculations predict a closed loop of gel-fluid coexistence with a lower critical mixing point. Specific-heat traces across the phase diagram are also presented. The theoretical results for the phase diagram, the specific-heat function, and the transition enthalpy are related to recent experimental measurements on phospholipid bilayers mixed with synthetic transmembrane amphiphilic polypeptides or with gramicidin A.
提出了一种统计力学晶格模型来描述含有小跨膜蛋白或多肽的磷脂双层膜的相图。该模型基于用于纯脂质双层膜的扩展的Pink-Green-Chapman模型（Zhang等人，《物理评论A》45卷，7560 - 7567页，1992年），纯脂质双层膜会经历一级凝胶-流体相变。利用疏水匹配的概念对脂质双层膜与蛋白质或多肽之间的相互作用进行建模。相图是通过计算机模拟技术得出的，该技术充分考虑了热密度涨落，并在自由能水平上进行运算，从而能够准确识别相边界。计算预测出具有较低临界混合点的凝胶-流体共存闭环。还给出了穿过相图的比热曲线。相图、比热函数和转变焓的理论结果与最近关于与合成跨膜两亲性多肽或短杆菌肽A混合的磷脂双层膜的实验测量结果相关。
