Chowdhry B Z, Dalziel A W
Biochemistry. 1985 Jul 16;24(15):4109-17. doi: 10.1021/bi00336a045.
The phase transition properties of dilute aqueous suspensions of "nonhydrated" (i.e., lipid suspensions which had not been heated above room temperature or above the main phase transition temperature of the fully hydrated lipid, whichever was lower) and hydrated 1,2(alpha)- and 1,3(beta)-dipalmitoylphosphatidylethanolamines with modified head groups have been determined by high-sensitivity differential scanning calorimetry at a scan rate of 0.1 K min-1. In both the 1,2 and 1,3 series, the head-group modifications of the phosphoethanolamine moiety included N-methyl, N,N-dimethyl, and N,N,N-trimethyl (phosphocholine). In the 1,2 series, additional modifications were dinitrophenyl, trinitrophenyl, N-(dinitrophenyl)aminocaproyl, N-(trinitrophenyl)aminocaproyl, and N-4-nitro-2,1,3-benzoxadiazole. Also included in this study were 1,2-dihexadecylphosphatidylethanolamine and the corresponding N-methyl-substituted lipid. In general, increasing bulkiness of the head-group substituent caused increasing lowering of the transition temperature, the most extreme cases among the hydrated lipids being the 45 degrees C lowering produced by the N-(dinitrophenyl)aminocaproyl substitution and its trinitrophenyl analogue in the 1,2 series. No simple trend is evident in the changes produced in the calorimetric enthalpy of transitions.
通过高灵敏度差示扫描量热法，以0.1 K min⁻¹的扫描速率测定了“非水合”（即未加热至室温以上或未加热至完全水合脂质的主相变温度以上，以较低者为准）和水合的、带有修饰头基的1,2(α)-和1,3(β)-二棕榈酰磷脂酰乙醇胺的稀水悬浮液的相变特性。在1,2和1,3系列中，磷酸乙醇胺部分的头基修饰包括N-甲基、N,N-二甲基和N,N,N-三甲基（磷酸胆碱）。在1,2系列中，额外的修饰有二硝基苯基、三硝基苯基、N-(二硝基苯基)氨基己酰基、N-(三硝基苯基)氨基己酰基和N-4-硝基-2,1,3-苯并恶二唑。本研究还包括1,2-二十六烷基磷脂酰乙醇胺和相应的N-甲基取代脂质。一般来说，头基取代基体积的增加导致转变温度的降低幅度增大，在水合脂质中最极端的情况是1,2系列中N-(二硝基苯基)氨基己酰基取代及其三硝基苯基类似物导致转变温度降低45℃。转变的量热焓变化没有明显的简单趋势。
