Denicourt N, Tancrède P, Brullemans M, Teissié J
Université du Québec à Trois-Rivières, Département de Chimie-Biologie, Canada.
Biophys Chem. 1989 Mar;33(1):63-70. doi: 10.1016/0301-4622(89)80008-0.
The fine details of the phase transition of dipalmitoylphosphoglycerocholine (DPPC) monolayers at air/NaCl solution interfaces were investigated at 21 +/- 1 degrees C by using the fluorescence after photobleaching technique employing 12-(9-anthroyloxy)stearic acid as fluorescent probe. The mode of compression of the monolayer (i.e., continuous compression or successive additions of the lipid at fixed area) together with the ionic strength of the subphase (0.1 or 1.0 M NaCl) were particularly studied. The photobleaching results show that the lateral diffusion coefficient of the probe molecules decreases drastically within the liquid-condensed phase, i.e., from the end of the liquid-expanded-liquid-condensed phase transition to the beginning of the solid-condensed phase. The molecular areas at which the phase transition occurs under the various experimental conditions, together with a parallel analysis of the hydration states and related molecular areas of the DPPC molecules in multilayers, strongly suggest that the steric hindrance associated with the hydration water of the polar head of DPPC molecules in the monolayer is responsible for the drastic decrease in diffusion coefficient in the liquid-condensed phase. Furthermore, the fluorescence characteristics of the probe molecules also show that, together with the aforementioned reorganization of the polar head, a structural reorganization of the aliphatic chains of the lipid molecules also takes place in the liquid-condensed phase. The liquid-condensed phase therefore appears as a transition region from liquid to solid phases in which the lipid molecules present a significant decrease in their lateral diffusion related to a structural reorganization of both their polar and aliphatic components.
在21±1℃下，采用光漂白后荧光技术，以12-(9-蒽氧基)硬脂酸为荧光探针，研究了二棕榈酰磷脂酰胆碱(DPPC)单层膜在空气/NaCl溶液界面的相变精细细节。特别研究了单层膜的压缩模式(即连续压缩或在固定面积下连续添加脂质)以及亚相的离子强度(0.1或1.0 M NaCl)。光漂白结果表明，在液晶相内，即从液-扩张-液-凝聚相变结束到固-凝聚相开始，探针分子的横向扩散系数急剧下降。在各种实验条件下发生相变的分子面积，以及对多层膜中DPPC分子的水合状态和相关分子面积的平行分析，强烈表明，与单层膜中DPPC分子极性头部的水合水相关的空间位阻是导致液晶相中扩散系数急剧下降的原因。此外，探针分子的荧光特性还表明，与上述极性头部的重组一起，脂质分子脂肪链的结构重组也发生在液晶相中。因此，液晶相表现为从液相到固相的过渡区域，在该区域中，脂质分子的横向扩散显著降低，这与它们的极性和脂肪族成分的结构重组有关。
