Morrow M R, Whitehead J P, Lu D
Department of Physics, Memorial University of Newfoundland, St. John's, Canada.
Biophys J. 1992 Jul;63(1):18-27. doi: 10.1016/S0006-3495(92)81579-5.
The temperature dependence of the mean orientational order parameter in the vicinity of the liquid crystal to gel phase transition is obtained from the first moment M1 of deuterium nuclear magnetic resonance spectra for bilayers of chain perdeuterated phosphatidylcholines with acyl chains of 12, 14, 16, and 18 carbons. The data clearly show an increasing temperature dependence of the orientational order parameter in the vicinity of the transition, with the effect becoming more pronounced with decreasing chain length. Assuming a linear relationship between the mean orientational order parameter and the extension of the acyl chain, estimates of the change in area of the membrane at the transition are shown to be consistent with those obtained from other measurements. It is shown that the transition may be modeled in terms of a Landau expansion of the free energy involving a small number of phenomenological parameters. From this it is shown that the behavior of these systems in the temperature range of interest is, in large part, controlled by the close proximity of a spinodal to the transition temperature.
通过对具有12、14、16和18个碳原子酰基链的全氘代磷脂酰胆碱双层膜的氘核磁共振谱的一阶矩M1，获得了液晶到凝胶相转变附近平均取向序参数的温度依赖性。数据清楚地表明，在转变附近取向序参数的温度依赖性增加，并且随着链长的减小，这种效应变得更加明显。假设平均取向序参数与酰基链的伸展之间存在线性关系，结果表明，转变时膜面积变化的估计值与从其他测量中获得的估计值一致。结果表明，该转变可以用涉及少量唯象参数的自由能的朗道展开来建模。由此表明，这些系统在感兴趣的温度范围内的行为在很大程度上受旋节线与转变温度的紧密接近程度控制。
