Davis J H
Biophys J. 1979 Sep;27(3):339-58. doi: 10.1016/S0006-3495(79)85222-4.
Deuterium magnetic resonance is applied to the study of the liquid crystalline and gel phases, and of the phase transition, of a multilamellar dispersion of chain perdeuterated (d62)-dipalmitoyl phosphatidylcholine/H2O. Analysis of the deuterium spectra in terms of the moments of the spectra allows one to make quantitative statements concerning the distribution of quadrupolar splittings even in complicated situations, e.g., when using perdeuterated sampled or when there are mixed phases. This analysis indicates that d62-dipalmitoyl phosphatidylcholine in excess H2O undergoes a sharp phase transition (with a width of less than 1 degree C) at approximately 37 degrees C and that there appears to be hysteresis in the phase transition of approximately 1 degree C. In the lamellar liquid crystalline phase above 37 degrees C the spectra show a number of well-resolved features whose quadrupolar splittings can be followed as the temperature is varied. The gel phase near 20 degrees C possesses a very broad, almost featureless spectrum that does not seem to support a model of the gel phase wherein the hydrocarbon chains are fully extended in the all-trans conformation. At temperatures near 0 degrees C the spectra clearly indicate that a large fraction of the lipid molecules cease the rotation about their long axes, giving a spectrum more characteristic of a rigid or solid sample. These results give a picture of the gel phase as a phase characterized by considerable hydrocarbon chain disorder near 20 degrees C and becoming a more solid-like phase near 0 degrees C. The spin-lattice relaxation time, T1, has been measured at 20 degrees C in the gel phase, and at 37 and 45 degrees C in the liquid crystalline phase. The values of T1 obtained for each of the resolvable peaks in the spectrum at 37 degrees C are compared to the values (for each peak) of T2e, the decay time of the quadrupolar echo, obtained at the same temperature. These results are discussed in terms of a simple two-motion model.
氘磁共振被应用于研究全氘代（d62）-二棕榈酰磷脂酰胆碱/H2O多片层分散体系的液晶相、凝胶相以及相变过程。根据光谱矩对氘光谱进行分析，即使在复杂情况下，例如使用全氘代样品或存在混合相时，也能够对四极分裂的分布进行定量描述。该分析表明，过量H2O中的d62-二棕榈酰磷脂酰胆碱在约37℃时会发生急剧的相变（宽度小于1℃），并且相变过程中似乎存在约1℃的滞后现象。在37℃以上的层状液晶相中，光谱显示出许多分辨率良好的特征，其四极分裂会随温度变化而变化。接近20℃的凝胶相具有非常宽的、几乎没有特征的光谱，这似乎不支持凝胶相模型，即碳氢链以全反式构象完全伸展的模型。在接近0℃的温度下，光谱清楚地表明，很大一部分脂质分子停止了围绕其长轴的旋转，从而产生了更具刚性或固体样品特征的光谱。这些结果描绘了凝胶相的图像，即在接近20℃时以相当大的碳氢链无序为特征，而在接近0℃时变为更类似固体的相。已经在20℃的凝胶相中以及37℃和45℃的液晶相中测量了自旋晶格弛豫时间T1。将在37℃时光谱中每个可分辨峰获得的T1值与在相同温度下获得的四极回波衰减时间T2e（每个峰）的值进行比较。根据一个简单的双运动模型对这些结果进行了讨论。
