Lentz B R, Freire E, Biltonen R L
Biochemistry. 1978 Oct 17;17(21):4475-80. doi: 10.1021/bi00614a018.
Discrepancies between calorimetric and fluorescence depolarization monitoring of the pretransition in multilamellar vesicles of synthetic phosphatidylcholines are shown to result primarily from the slow rate of this transition. The depolarization of fluorescence of the membrane-associated dye 1,6-diphenyl-1,3,5-hexatriene was used to determine the temperature of the pretransition for a series of heating and cooling scan rates. These temperatures, when plotted vs. scan rate, extrapolated linearly to the transition temperature at zero-scan rate, Tm = 29.8 +/- 0.8 degrees C. The slopes obtained from these plots yielded characteristic times for the transition of 8 to 30 min. In addition, analysis of temperature-jump experiments, assuming first-order kinetics, gave characteristic times in the range 4--8 min. The data are taken to suggest a most likely value for the pretransition characteristic time of 5 +/- 2 min, with larger values possibly explainable by supercooling effects. Slight differences between the calorimetrically and fluorimetrically determined main transition temperatures appear to result from perturbation of the phosphatidylcholine bilayer by the fluorescent probe.
合成磷脂多层囊泡预转变过程中量热法和荧光去极化监测之间的差异表明，主要是由于该转变速率缓慢所致。利用膜相关染料1,6 - 二苯基 - 1,3,5 - 己三烯的荧光去极化来确定一系列加热和冷却扫描速率下的预转变温度。当将这些温度与扫描速率作图时，线性外推至零扫描速率下的转变温度，Tm = 29.8±0.8℃。从这些图中获得的斜率得出转变的特征时间为8至30分钟。此外，假设为一级动力学对温度跃升实验进行分析，得到的特征时间在4 - 8分钟范围内。数据表明预转变特征时间的最可能值为5±2分钟，较大的值可能由过冷效应解释。量热法和荧光法测定的主要转变温度之间的细微差异似乎是由荧光探针扰动磷脂酰胆碱双层所致。
