Katsu T, Akagi M, Hiramatsu T, Tsuchiya T
Faculty of Pharmaceutical Sciences, Okayama University, Tsushima, Japan.
Analyst. 1998 Jun;123(6):1369-72. doi: 10.1039/a801686k.
A method was developed for determining pH differences across cell membranes using a methylammonium-selective membrane electrode, based on monitoring of the pH gradient-induced uptake of methylammonium in situ. The methylammonium electrode was constructed using calix[6]arene-hexaacetic acid hexaethyl ester as a neutral carrier and bis(2-ethylhexyl) sebacate as a membrane solvent in a poly(vinyl chloride) membrane matrix. This electrode exhibited a near-Nernstian response to methylammonium in the concentration range 2 x 10(-5)-1 x 10(-2) M with a slope of 58 mV per concentration decade in a buffer solution of 150 mM choline chloride-10 mM TRIS-HCl (pH 7.5). The limit of detection was 5 x 10(-6) M. In experiments using liposomes, the uptake of methylammonium into liposomes occurred effectively when the pH of the outside suspension medium was alkaline, and the determination of changes in methylammonium concentrations in the outer medium was quantitatively related to changes in the pH differences across the liposomal membrane. The transmembrane pH differences in Escherichia coli cells were also determined by this method.
基于原位监测pH梯度诱导的甲铵摄取，开发了一种使用甲铵选择性膜电极测定跨细胞膜pH差异的方法。甲铵电极是在聚氯乙烯膜基质中，以杯[6]芳烃六乙酸六乙酯作为中性载体、癸二酸二（2-乙基己基）酯作为膜溶剂构建而成。在150 mM氯化胆碱-10 mM三羟甲基氨基甲烷盐酸盐（pH 7.5）的缓冲溶液中，该电极对浓度范围为2×10⁻⁵至1×10⁻² M的甲铵呈现近能斯特响应，每浓度 decade 的斜率为58 mV。检测限为5×10⁻⁶ M。在使用脂质体的实验中，当外部悬浮介质的pH呈碱性时，甲铵有效地摄取到脂质体中，并且外部介质中甲铵浓度变化的测定与跨脂质体膜的pH差异变化定量相关。大肠杆菌细胞中的跨膜pH差异也通过该方法测定。
