Jackson M B
Biochemistry. 1976 Jun 15;15(12):2555-61. doi: 10.1021/bi00657a011.
A statistical-mechanical model for a lipid bilayer was built around the assumption that beta-coupled gauche kinks are the only nonstraight hydrocarbon chain configurations allowed. Packing of these chains was considered and expressions for the energy and entropy are developed based on those considerations. A solution was obtained which was not exact but was still accurate enough to be useful. In addition, an intermolecular potential was formulated which includes the attractive and repulsive forces between the hydrocarbon chains, the polar group repulsions, and hydrophobic forces. Combining the solution to the kinking model and the intermolecular potential, we obtain the total free energy of the lipid bilayer, which exhibits a first-order phase transition at a characteristic temperature. The theoretical heat of transition indicates that kinks alone can provide enough disorder for the transition to occur. Other physical quantities can be calculated, including order parameters. The order parameters calculated here give a picture of chains which are rigid near the polar group and more fluid near the methyl group.
围绕β-耦合gauche扭结是唯一允许的非直链烃链构型这一假设，构建了脂质双层的统计力学模型。考虑了这些链的堆积情况，并基于这些考虑推导出了能量和熵的表达式。得到了一个并非精确但仍足够准确以有用的解。此外，还制定了一种分子间势，其中包括烃链之间的吸引力和排斥力、极性基团排斥力以及疏水力。将扭结模型的解与分子间势相结合，我们得到了脂质双层的总自由能，其在特征温度下表现出一级相变。理论转变热表明，仅扭结就能为相变的发生提供足够的无序度。还可以计算其他物理量，包括序参量。这里计算的序参量给出了一幅链在极性基团附近刚性较强而在甲基附近流动性较强的图像。
