Abstract

It has been shown that electrochromic styryl dyes can be used as probes to study proton binding on the membrane surface. These dyes are adsorbed on the membrane as neutral molecules with a significant dipole moment, due to which a dipole potential jump occurs at the boundary of the membrane with the solution. A decrease in pH led to the disappearance of both this potential jump and fluorescence of the membrane-bound molecules of dyes di-4-ANEPPS and RN-421. This can be explained by the inability of protonated dye molecules formed at low pH to adsorb on lipid membranes. The dependence of the dipole potential jump on pH was measured in the experiment to estimate pK of the dyes, which was estimated to be about 4.5. Desorption of the dye molecules from the surface of the lipid membrane occurred not only under the solution pH decrease, but also upon photoactivated release of protons on the membrane surface caused by photolysis of the caged-H⁺ molecules of sodium 2-methoxy-5-nitrophenyl sulfate. This indicated a significant increase in the concentration of protons on the surface of the lipid membrane caused by this process.

中文翻译：

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苯乙烯染料 di-4-ANEPPS 和 RH-421 作为脂质膜表面质子的传感器

摘要

已经表明，电致变色苯乙烯染料可用作研究膜表面质子结合的探针。这些染料作为具有显着偶极矩的中性分子吸附在膜上，因此在膜与溶液的边界处发生偶极电位跳跃。pH 值的降低导致染料 di-4-ANEPPS 和 RN-421 的膜结合分子的这种电位跳跃和荧光消失。这可以通过在低 pH 值下形成的质子化染料分子无法吸附在脂质膜上来解释。在实验中测量偶极电位跳跃对 pH 的依赖性，以估计染料的 pK，估计约为 4.5。染料分子从脂质膜表面的解吸不仅发生在溶液 pH 降低下，⁺ 2-甲氧基-5-硝基苯基硫酸钠分子。这表明由该过程引起的脂质膜表面质子浓度显着增加。