The phase transition kinetics and mechanism of formation of a lamellar-crystalline phase of dipalmitoylphosphatidylethanolamine (DPPE) dispersed in different concentrations of aqueous dimethyl sulfoxide (DMSO) during cooling have been examined by differential scanning calorimetry and synchrotron X-ray diffraction techniques. In dispersions containing mole fractions of DMSO (x<0.22), the phase transition sequence of the phospholipid is from lamellar liquid-crystal phase to lamellar-gel phase. Increasing the mole fraction of DMSO to 0.220.5 resulted in a direct transition from liquid-crystal phase to lamellar crystal phase with no detectable intermediate gel phase. A temperature versus DMSO concentration phase diagram was constructed based on calorimetric data with phase assignments made using synchrotron X-ray diffraction measurements. The non-isothermal formation kinetics of the lamellar crystal phase, which is expressed as the half time of the transformation process, was found to depend on DMSO concentration. The inducement of lamellar crystal phase in DPPE by DMSO is discussed in terms of the dehydration effect of DMSO and competitive molecular interactions between DMSO, water, and the phospholipid.

中文翻译：

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分散在二甲基亚砜水溶液中的二棕榈酰磷脂酰乙醇胺形成结晶相的动力学和机理。

通过差示扫描量热法和同步加速器X射线衍射技术研究了冷却过程中分散在不同浓度的二甲基亚砜（DMSO）中的二棕榈酰磷脂酰乙醇胺（DPPE）的层状结晶相的相变动力学和形成机理。在包含DMSO的摩尔分数（x ＜0.22）的分散体中，磷脂的相变序列是从层状液晶相到层状凝胶相。将DMSO的摩尔分数提高到0.220.5导致从液晶相到层状晶相的直接转变，而没有可检测的中间凝胶相。基于量热数据构建温度对DMSO浓度的相位图，并使用同步加速器X射线衍射测量进行相位分配。层状晶相的非等温形成动力学表示为转化过程的一半时间，取决于DMSO浓度。根据DMSO的脱水作用以及DMSO，水和磷脂之间的竞争性分子相互作用，讨论了DMSO在DPPE中诱导层状晶相。