Ono A, Miyauchi S, Demura M, Asakura T, Kamo N
Laboratory of Biophysical Chemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
Biochemistry. 1994 Apr 12;33(14):4312-8. doi: 10.1021/bi00180a027.
The conductance caused by translocation of various phosphonium cations across phospholipid (from soybean) bilayer membrane was measured. Phosphonium cations used were tetraphenylphosphonium (TPP+) and triphenylalkylphosphonium cations formulated as (Phe)3-P(+)-(CH2)nCH3 (n = 0-5). The conductance was dependent on voltage applied externally to the membrane in accordance with a theory developed by previous authors. Using the theory, values of beta K(i) were determined, where beta and k(i) are a linear partition coefficient and a rate constant of transmembrane ion transport, respectively. Since beta k(i) depended on the phosphonium ion concentration, values extrapolated to infinite dilution, (beta k(i))0, were determined. Temperature dependence of (beta k(i))0 allowed us to estimate the activation energy of transport, Ea. For TPP+ thermodynamic values obtained were consistent with values calculated by Flewelling and Hubbell [(1986) Biophys. J. 49, 541-552]. When (Phe)3-P(+)-(CH2)nCH3 (n = 0-5) were used, E(a) depended on the odd or even of n. This "odd and even" pattern was observed in a variety of phenomena such as solubility in water, equivalent ionic conductivity in water, and 31P NMR chemical shift.
测量了各种鏻阳离子跨磷脂（来自大豆）双层膜转运所引起的电导。所使用的鏻阳离子为四苯基鏻（TPP+）和化学式为(Phe)3-P(+)-(CH2)nCH3（n = 0 - 5）的三苯基烷基鏻阳离子。根据先前作者提出的理论，电导取决于施加在膜上的外部电压。利用该理论，确定了βK(i)的值，其中β和k(i)分别是线性分配系数和跨膜离子转运的速率常数。由于βk(i)取决于鏻离子浓度，因此确定了外推至无限稀释时的值，即(βk(i))0。(βk(i))0的温度依赖性使我们能够估算转运的活化能Ea。对于TPP+，所获得的热力学值与Flewelling和Hubbell计算的值[(1986) Biophys. J. 49, 541 - 552]一致。当使用(Phe)3-P(+)-(CH2)nCH3（n = 0 - 5）时，E(a)取决于n的奇偶性。这种“奇偶”模式在多种现象中都有观察到，如水溶性、水中的当量离子电导率和31P NMR化学位移。
