Lipschitz-Farber C, Degani H
Biochim Biophys Acta. 1980 Aug 4;600(2):291-300. doi: 10.1016/0005-2736(80)90433-2.
Nuclear relaxation measurements of 1H and 17O of water have been applied to study the kinetics of water diffusion across vesicular lipid membranes. Differentiation between the intra- and extravesicular media was achieved by entrapping Mn2+ inside the vesicles. The water permeability of egg phosphatidylcholine vesicles was found to be 2.9 x 10(-3) cm/s at 25 degrees C, with an activation energy of 10.5 kcal/mol which remains constant through the temperature range 0-65 degrees C. The water permeability across vesicular bilayers of L-alpha-dipalmitoyl phosphatidylcholine exhibited a sharp change through the lipid phase transition. The permeability in the lipid crystalline phase (45 degrees C) was found to be 7.2 x 10(-3) cm/s with an activation energy of 7.2 kcal/mol. Below the transition at the gel phase (35 degrees C) a permeability of 1.0 x 10(-3) cm/s was determined. The results indicate that water diffuses through lipid membranes in the liquid crystalline phase in a similar fashion to its diffusion in hydrocarbon liquids. However, when the lipids undergo a phase transition to the gel state, this similarity does not hold any more and water diffusion becomes much more restricted than in hydrocarbon liquids. The change in water permeability through the phase transition was correlated with the changes observed in the lipid segmental motion determined from 13C T1 measurements.
已应用水的1H和17O的核弛豫测量来研究水跨囊泡脂质膜扩散的动力学。通过将Mn2+包裹在囊泡内部实现了囊泡内和囊泡外介质的区分。发现卵磷脂酰胆碱囊泡在25℃时的水渗透率为2.9×10(-3) cm/s，活化能为10.5 kcal/mol，在0 - 65℃的温度范围内保持恒定。L-α-二棕榈酰磷脂酰胆碱囊泡双层的水渗透率在脂质相变过程中呈现出急剧变化。在脂质结晶相（45℃）中的渗透率为7.2×10(-3) cm/s，活化能为7.2 kcal/mol。在低于凝胶相的转变温度（35℃）时，测定的渗透率为1.0×10(-3) cm/s。结果表明，水在液晶相中通过脂质膜扩散的方式与其在烃类液体中的扩散方式相似。然而，当脂质经历向凝胶态的相变时，这种相似性不再成立，水的扩散比在烃类液体中受到更多限制。通过相变的水渗透率变化与由13C T1测量确定的脂质链段运动中观察到的变化相关。
