The apparent permeability coefficient for proton flux through phosphatidylcholine vesicles is dependent on the direction of flux.
The apparent permeability coefficient for proton flux through phosphatidylcholine vesicles is dependent on the direction of flux.
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质子通量通过磷脂酰胆碱囊泡的表观渗透系数取决于通量的方向。
DOI：
10.1016/0005-2736(90)90252-j
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发表时间：
1990
期刊：
影响因子：
--
通讯作者：
Powell,GL
中科院分区：
文献类型：
--
作者：
Norris,FA;Powell,GL
使用二油酰磷脂酰胆碱单层囊泡模型系统来测定质子渗透性。 pH 报告基团吡喃的荧光被捕获在跨双层 pH 值不同的囊泡内，并通过数值积分进行数字化和分析。当通过外部缓冲液的酸化（酸跃）引发 H+ 通量时，发现表观 H+ 渗透率是内部 H+ 浓度倒数的线性函数，斜率与 H+ 梯度的初始大小成反比。当通过外部缓冲液的碱化（碱基跳跃）启动通量时，对于每个外部 H+ 浓度，表观渗透系数是恒定的。然而，表观渗透率的值与外部 H+ 的倒数线性相关。通过向碳酸盐大大减少的溶液中添加毫摩尔浓度的碳酸氢盐，测试了碳酸盐（二氧化碳、碳酸、碳酸氢盐和碳酸盐）充当质子载体的可能性。对于酸和碱跃条件，表观渗透系数与 H+ 倒数的曲线图的斜率是添加的碳酸氢盐浓度的线性函数。这些观察结果根据一个模型进行了解释，该模型表明碳酸或二氧化碳与碳酸氢盐一起是穿过磷脂双层的有效质子载体。
A dioleoylphosphatidylcholine unilamellar vesicle model system was used to determine proton permeability. The fluorescence of the pH reporter group, pyranine, trapped within vesicles with a difference in pH across the bilayer, was digitized and analyzed with numerical integration. When H+flux was initiated by the acidification of the external buffer (acid jump), the apparent H+permeability was found to be a linear function of the reciprocal of the internal H+concentration with the slope inversely proportional to the initial size of the H+gradient. When flux was initiated by the alkalinization of the external buffer (base jump), the apparent permeability coefficient was constant for each external H+concentration. However, the value of the apparent permeability was linearly dependent on the reciprocal of the external H+. The possibility that carbonates (carbon dioxide, carbonic acid, bicarbonate and carbonate) could be acting as proton carriers was tested by adding millimolar concentrations of bicarbonate to solutions greatly reduced in carbonates. The slopes of the graphs of apparent permeability coefficient vs. reciprocal H+were linear functions of added bicarbonate concentration for both acid and base jump conditions. These observations were interpreted in terms of a model suggesting that carbonic acid or carbon dioxide together with bicarbonate was an efficient proton carrier across phospholipid bilayers.