Faculty of Molecular Chemistry and Engineering, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan.
Analyst. 2020 Jun 7;145(11):3839-3845. doi: 10.1039/d0an00222d. Epub 2020 Apr 7.
To examine the transport of an ionic substance through a bilayer lipid membrane (BLM), an electrochemical method combined with fluorometry was proposed. In this method, the transport of a fluorescent ion through the BLM was detected both as the transmembrane current and the dynamic change of fluorescence intensity synchronizing scanning membrane potential. The fluorescence intensity was measured in the local area close to the planar BLM by utilizing a confocal fluorescence microscope. The electrochemical method combined with fluorometry makes it possible to analyze only the transport of a target fluorescent ion in distinction from the transport of other coexisting ions. With the proposed electrochemical method, the ion transport caused by both a hydrophobic fluorescent cation (rhodamine 6G, R6G) and a relatively hydrophobic anion (BF) was examined. The electrochemical method combined with fluorometry characterized the transmembrane current as the transport of R6G. Membrane conductance for the R6G transport increased proportionally to the concentrations of R6G and BF distributed in the hydrocarbon medium of the BLM which were estimated by extraction experiments with liposomes. These results show that the distribution of a cation and an anion from the aqueous phase in the BLM predominantly controls the membrane conductance for ion transport through the BLM.
为了研究离子物质通过双层脂质膜（BLM）的传输，提出了一种电化学方法与荧光法相结合的方法。在这种方法中，通过同步扫描膜电位，同时检测荧光离子穿过 BLM 的跨膜电流和荧光强度的动态变化，来检测荧光离子的传输。利用共焦荧光显微镜在靠近平面 BLM 的局部区域测量荧光强度。电化学方法与荧光法相结合，可以分析只有目标荧光离子的传输，而与其他共存离子的传输区分开来。利用所提出的电化学方法，研究了疏水性荧光阳离子（若丹明 6G，R6G）和相对疏水性阴离子（BF）的离子传输。电化学方法与荧光法相结合，将跨膜电流特征化为 R6G 的传输。R6G 传输的膜电导与估计通过脂质体提取实验在 BLM 的烃类介质中分布的 R6G 和 BF 的浓度成正比。这些结果表明，从 BLM 中的水相到阳离子和阴离子的分布主要控制通过 BLM 的离子传输的膜电导。
