Kuo K H, Fukuto T R, Miller T A, Bruner L J
Biophys J. 1976 Feb;16(2 Pt 1):143-50. doi: 10.1016/s0006-3495(76)85671-8.
Valinomycin selectively transports alkali cations, e.g. potassium ions, across lipid bilayer membranes. The blocking of this carrier-mediated transport by four substituted benzimidazoles has been investigated. The compounds are 4,5,6,7-tetrachloro-2-trifluoromethylbenzimidazole, (TTFB); 4,5,6,7,-tetrachloro-2-methylbenzimidazole, (TMB); 2-trifluoromethylbenzimidazole, (TFB); and 2-methylbenzimidazole, (MBM). Because of its low acidic dissociation constant (pKa = 5.04), the blocking efficiency of TTFB in both neutral and anionic forms in the aqueous phase could be studied. The compounds exhibit the blocking efficiency sequence, TTFB- greater than TTFB0 greater than TMB0 greater than TFB0 greater than MBM0. The corresponding scale of decreasing lipophilicity, as determined by octanol/water partitioning, is TTFB0 greater than TMB0 greater than TTFB- greater than TFB0 greater than MBM0. Comparison of neutral species establishes a positive correlation of blocking efficiency with lipophilicity, with the latter being conferred primarily by chlorination of the benzenoid nucleus. Anionic TTFB, on the other hand, is the most effective blocking agent studied in spite of the fact that its dissociation in the aqueous phase markedly impedes its entry (presumably as a neutral species) into a bulk hydrocarbon phase. This observation suggests that the blocking of valinomycin-mediated bilayer membrane conductance takes place at the membrane/solution interface.
缬氨霉素可选择性地将碱金属阳离子（如钾离子）转运穿过脂质双分子层膜。研究了四种取代苯并咪唑对这种载体介导转运的阻断作用。这些化合物分别是4,5,6,7-四氯-2-三氟甲基苯并咪唑（TTFB）、4,5,6,7-四氯-2-甲基苯并咪唑（TMB）、2-三氟甲基苯并咪唑（TFB）和2-甲基苯并咪唑（MBM）。由于TTFB的酸解离常数较低（pKa = 5.04），因此可以研究其在水相中中性和阴离子形式的阻断效率。这些化合物的阻断效率顺序为：TTFB-＞TTFB0＞TMB0＞TFB0＞MBM0。通过正辛醇/水分配测定的相应亲脂性降低程度顺序为：TTFB0＞TMB0＞TTFB-＞TFB0＞MBM0。对中性物质的比较表明，阻断效率与亲脂性呈正相关，亲脂性主要由苯环的氯化作用赋予。另一方面，阴离子形式的TTFB是所研究的最有效的阻断剂，尽管其在水相中的解离明显阻碍了它（可能以中性物质形式）进入大量烃相。这一观察结果表明，缬氨霉素介导的双分子层膜电导的阻断发生在膜/溶液界面。
