Elamrani K, Blume A
Biochim Biophys Acta. 1983 Jan 5;727(1):22-30. doi: 10.1016/0005-2736(83)90364-4.
The kinetics of H+/OH- diffusion across dimyristoyl phosphatidic acid bilayer membranes was measured by following the absorbance of the pH-sensitive indicator Cresol red (o-cresolsulfonphthalein) entrapped in single lamellar vesicles after rapidly changing the external pH in a stopped-flow apparatus. The H+/OH- permeability coefficient was found to be in the 10(-5) to 10(-3) cm . s-1 range. The lipid phase transition has a strong influence on the permeation kinetics as the permeability coefficients in the liquid-crystalline phase are drastically higher. The permeability shows no maximum at the phase transition temperature as is the case for other ions, but displays a similar temperature dependence as water permeation. This is also reflected in the high activation energy of approx. 20 kcal/mol and supports the hypothesis (Nichols, J.W. and Deamer, D.W. (1980) Proc. Natl. Acad. Sci. U.S.A. 77, 2038-2042) of H+/OH- permeation via hydrogen bonded water molecules. A second slower kinetic phase is also observed, where the permeation is obviously controlled by counterion diffusion. The temperature dependence of this slow process displays the for ion diffusion characteristic maximum in the permeability at the phase-transition temperature.
通过在停流装置中快速改变外部pH值后，跟踪包裹在单层囊泡中的pH敏感指示剂甲酚红（邻甲酚磺酞）的吸光度，来测量H⁺/OH⁻跨二肉豆蔻酰磷脂酸双层膜的扩散动力学。发现H⁺/OH⁻渗透系数在10⁻⁵至10⁻³cm·s⁻¹范围内。脂质相变对渗透动力学有很大影响，因为液晶相中的渗透系数要高得多。与其他离子的情况不同，渗透率在相变温度处没有最大值，而是表现出与水渗透相似的温度依赖性。这也反映在约20千卡/摩尔的高活化能上，并支持了H⁺/OH⁻通过氢键水分子渗透的假说（Nichols, J.W.和Deamer, D.W.（1980年）《美国国家科学院院刊》77, 2038 - 2042）。还观察到第二个较慢的动力学阶段，其中渗透明显受抗衡离子扩散控制。这个缓慢过程的温度依赖性显示出离子扩散在相变温度处渗透率具有特征性最大值。
