Phase behavior of synthetic phosphatidylglycerols and binary mixtures with phosphatidylcholines in the presence and absence of calcium ions.
Phase behavior of synthetic phosphatidylglycerols and binary mixtures with phosphatidylcholines in the presence and absence of calcium ions.
复制标题
存在和不存在钙离子时合成磷脂酰甘油和磷脂酰胆碱二元混合物的相行为。
作者：
E. Findlay;P. G. Barton
采用差热分析、扫描量热法和光散射法，测定了5种合成磷脂酰甘油钠盐（PG-Na+）从凝胶到液晶的相变温度和相变焓。所得值与相应磷脂酰胆碱（PC）的文献值几乎相同。然而，饱和磷脂酰甘油（PG-H+）的完全质子化形式的转变温度高出约20 ℃。对于PG-Na+和PC的二元混合物，其中两个物种的酰基链是相同的，相变的热转变的宽度是不是明显大于观察到的两个组件单独的。相反，混合PG-Na+和PC与不同的链长增加的过渡宽度。在Ca ~（2+）存在下，当PG-Ca ~（2+）的链长等于或短于PC时，PG和PC的混合物也观察到窄的跃迁，但当PG-Ca ~（2+）的链长大于PC时，跃迁宽度明显增加。混合脂质与更大的差异，在链长或混合饱和脂质与不饱和脂质的存在下的Ca 2+产生两个最小值的热谱图，清楚地表明相分离。总之，这些结果提供了证据的磷酸甘油和磷酸胆碱头基团的高度可溶解性，无论是在存在或不存在的Ca 2+，使得每种混合物的特征相行为主要是由烃链结构的差异确定。
Using differential thermal analysis, scanning calorimetry and light scattering, transition temperatures and enthalpy data for the gel to liquid crystalline phase transitions of five synthetic phosphatidylglycerol sodium salts (PG-Na+) were measured. The values obtained were almost identical with literature values for the corresponding phosphatidylcholines (PC). However, transition temperatures for the fully protonated forms of the saturated phosphatidylglycerols (PG-H+) were approximately 20 degrees C higher. For binary mixtures of PG-Na+ and PC in which the acyl chains of the two species were identical, the width of the thermal transition for the phase change was not appreciably greater than that observed with either of the two components alone. In contrast, mixing of PG-Na+ and PC with different chain lengths increases the transition width. In the presence of Ca2+, narrow transitions were also observed with mixtures of PG and PC when the chain length of the PG-Ca2+ was equal to or two carbons shorter than the PC but the transition width was clearly increased when the chain length of the PG-Ca2+ was two carbons longer than the PC. Mixing lipids with greater differences in chain length or mixing saturated lipids with unsaturated lipids in the presence of Ca2+ produced two minima in the thermograms, clearly indicative of phase separation. In sum, these results provide evidence for a high degree of miscibility of the phosphoglycerol and phosphocholine head groups, either in the presence or absence of Ca2+, such that the characteristic phase behavior of each mixture is determined primarily by differences in the hydrocarbon chain structure.