Antonenko Y N, Kovbasnjuk O N, Yaguzhinsky L S
A.N. Belozersky Institute of Physico-chemical Biology, Moscow State University, Russian Federation.
Biochim Biophys Acta. 1993 Jul 25;1150(1):45-50. doi: 10.1016/0005-2736(93)90119-k.
When the hydrogen-ion flux is induced by nigericin across the planar bilayer lipid membrane (BLM) with bulk pH values being equal at the opposite sides of the BLM, formation of a difference in boundary potentials (delta phi b) on the membrane is observed by the method of inner membrane field compensation. pH gradients are titrated routinely by the addition of sodium acetate at one side of the membrane. The increase in buffer concentration (citrate, phosphate, Mes) leads to a decrease in delta phi b. delta phi b forms in the presence of phosphatidylserine in the membrane-forming solution only. It is concluded that the steady-state difference of the hydrogen ion binding to the opposite surfaces of the membrane (HIBD) is created under the conditions of equal pH values near surfaces of the BLM. The model of the processes implies that nigericin transfers proton predominantly from interface to interface while acetate transfers the proton from bulk phase to bulk phase. In the other series of experiments the monensin-mediated formation of the HIBD leads to the formation of an potassium-ion gradient in the presence of nigericin. Thus, a possibility of performing a work due to the formation of HIBD is demonstrated. Owing to these properties the hydrogen-ion binding difference can be interpreted in a first approximation as a difference of surface hydrogen-ion concentration at the opposite sides of the membrane, arising due to the existence of a kinetic barrier for the proton transfer at the membrane interfaces. These findings can be significant for the mechanism of energy transduction in membrane phosphorylation in mitochondria and chloroplasts.
当尼日利亚菌素在平面双层脂质膜（BLM）上诱导氢离子通量，且BLM两侧的本体pH值相等时，通过内膜场补偿法可观察到膜上边界电位差（δφb）的形成。通常通过在膜的一侧添加醋酸钠来滴定pH梯度。缓冲液浓度（柠檬酸盐、磷酸盐、MES）的增加会导致δφb减小。仅在形成膜的溶液中存在磷脂酰丝氨酸时才会形成δφb。得出的结论是，在BLM表面附近pH值相等的条件下，会产生膜相对表面氢离子结合的稳态差异（HIBD）。这些过程的模型表明，尼日利亚菌素主要将质子从一个界面转移到另一个界面，而醋酸盐则将质子从本体相转移到本体相。在另一系列实验中，莫能菌素介导的HIBD形成在存在尼日利亚菌素的情况下导致钾离子梯度的形成。因此，证明了由于HIBD的形成而进行功的可能性。由于这些特性，氢离子结合差异在一级近似中可解释为膜相对两侧表面氢离子浓度的差异这是由于膜界面处质子转移存在动力学屏障而产生的。这些发现对于线粒体和叶绿体中膜磷酸化的能量转导机制可能具有重要意义。
