Rand R P, Chapman D, Larsson K
Biophys J. 1975 Nov;15(11):1117-24. doi: 10.1016/S0006-3495(75)85888-7.
Differential scanning calorimetry studies of dipalmitoyl lecithin show two reversible transitions as the temperature is changed between 20 and 50 degrees C. A pretransition endotherm occurs at 35 degrees C prior to the main chain melting endotherm which occurs at 42 degrees C. X-ray diffraction studies show that below 33 degrees C the chains of the lecithin are fully extended, packed in a hexagonal crystalline lattice but tilted with respect to the plane of the bilayer. Between 35 and 42 degrees C the chains are similarly packed but oriented perpendicular to the bilayer plane. Above 44 degrees C the chains are "melted" or disordered. Monolayer studies of dipalmitoyl lecithin using continuous recording of pressure with molecular area reveal the existence of two solid condensed phases corresponding to these tilted and verticle chain structures. The tilted to perpendicular transition would account for the pretransition endotherm of the lipid; the crystalline to melted change corresponds to the larger transition observed at 42 degrees C.
对二棕榈酰卵磷脂进行差示扫描量热法研究表明，当温度在20至50摄氏度之间变化时，会出现两个可逆转变。在主链熔化吸热峰（发生在42摄氏度）之前，在35摄氏度处会出现一个预转变吸热峰。X射线衍射研究表明，在33摄氏度以下，卵磷脂的链完全伸展，堆积在六方晶格中，但相对于双层平面倾斜。在35至42摄氏度之间，链的堆积方式相似，但垂直于双层平面排列。在44摄氏度以上，链“熔化”或无序。使用分子面积连续记录压力对二棕榈酰卵磷脂进行的单层研究揭示了对应于这些倾斜和垂直链结构的两个固体凝聚相的存在。从倾斜到垂直的转变可以解释脂质的预转变吸热峰；从结晶到熔化的变化对应于在42摄氏度处观察到的较大转变。
