Characterization of CO2/carbonic acid mediated proton flux through phosphatidylcholine vesicles as model membranes.
Characterization of CO2/carbonic acid mediated proton flux through phosphatidylcholine vesicles as model membranes.
复制标题
CO2/碳酸介导的通过磷脂酰胆碱囊泡作为模型膜的质子通量的表征。
DOI：
10.1016/0005-2736(92)90269-r
复制
发表时间：
1992
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
我们实验室测量的磷脂囊泡的表观质子渗透系数（Norris, F.A. 和 Powell, G.L. (1990) Biochim. Biophys. Acta 1030, 165–171）通过快速降低外部 pH 值（酸跃）引发的质子通量是内部质子浓度倒数的线性函数。这种行为归因于弱酸载体碳酸/CO2/碳酸氢盐的存在。在目前的工作中，已经开发了适用于任何弱酸载体的质子传输的理论描述，该理论描述有助于新颖的图形处理，允许单独估计质子、氢氧根离子和碳酸氢根的渗透系数。该方法测定的质子渗透系数为1.8·10−5(S.E.1.3·10−5)cm/s；氢氧根离子的渗透率下限为3.8·10−5(S.E. 5.6·10−6) cm/s，碳酸氢根离子的渗透率下限为4.3·10−6(S.E. 3.6·10−7) cm/s。根据 Gouy-Chapman 理论，脂质双层上负表面电荷的存在增加了观察到的质子渗透系数。通过制备含有越来越多的带负电荷的二油酰磷脂酰甘油的囊泡来引入电荷。观察到的质子渗透系数增加，观察到的氢氧根离子和碳酸氢根渗透系数降低。亲脂性阳离子缬氨霉素-K+和四丁基铵离子的添加增加了Pvs的斜率。 1/[嗨+]。这些变化与报道的渗透性弱酸解偶联剂 FCCP 和 CCCP 的变化类似。这些研究表明，CO2/碳酸是质子穿过磷脂模型膜的有效载体。
The apparent proton permeability coefficient for phospholipid vesicles measured in our laboratory (Norris, F.A. and Powell, G.L. (1990) Biochim. Biophys. Acta 1030, 165–171) for proton flux initiated by rapidly lowering of the external pH (acid jump) was a linear function of the reciprocal internal proton concentration. This behavior was ascribed to the presence of the weak acid carriers, carbonic acid/CO2/bicarbonate. In the present work, a theoretical description, appropriate for proton transport by any weak acid carrier, has been developed which lends itself to novel graphical treatment permitting the separate estimation of the permeability coefficients for protons, hydroxide ions and bicarbonate. The proton permeability coefficient determined by this method was 1.8 · 10−5(S.E. 1.3 · 10−5) cm/s; that for hydroxide ion was 3.8 · 10−5(S.E. 5.6 · 10−6) cm/s and a lower limit for the permeability of bicarbonate ion, 4.3 · 10−6(S.E. 3.6 · 10−7) cm/s, can be set. The presence of negative surface charge on the lipid bilayer increased the observed proton permeability coefficient in accordance with Gouy-Chapman theory. The charge was introduced by preparing vesicles containing increasing amounts of negatively charged dioleoylphosphatidylglycerol. The observed proton permeability coefficient increased and the observed permeability coefficients for hydroxide ion and bicarbonate decreased. The addition of the lipophilic cations, valinomycin-K+and tetrabutylammonium ion increased the slope ofPvs. 1/[Hi+]. These changes are analogous to those reported for the permeant weak acid uncouplers FCCP and CCCP. These studies demonstrated that CO2/carbonic acid was an effective carrier of protons across phospholipid model membranes.