Department of Physical and Analytical Chemistry, Uppsala University, Husargatan 3, Box 579, 75123, Uppsala, Sweden.
Bioelectrochemistry. 2012 Dec;88:171-80. doi: 10.1016/j.bioelechem.2012.03.009. Epub 2012 Apr 11.
It is reported that the reduction of ubiquinone incorporated into supported lipid bilayers and into immobilized liposome layers on gold electrodes is kinetically and thermodynamically enhanced by the presence of acetylcholine and tetrabutylammonium (TBA(+)) in solution. The reduction peak and the mid-peak potentials of the redox reactions, determined by cyclic voltammetry, are displaced towards more positive potentials by approximately 500 and 250mV, respectively, in the case of TBA(+); and by approximately 750 and 530mV, respectively, in the case of acetylcholine. The intensity of the signal varies with the cation concentration, allowing for quantitative determinations in the millimolar range. It is proposed that the enhanced reduction of ubiquinone arises from the formation of tetraalkylammonium cation-ubiquinone radical anion ion-pairs. Electrochemical quartz crystal microbalance with dissipation monitoring (EQCM-D) measurements confirmed that the potential shift and the intensity of the redox signal are coupled with the adsorption of the tetraalkylammonium cations on the lipid membrane. The Langmuir adsorption equilibrium constant (K) of TBA(+) on lipid membranes at physiological pH is determined. In supported lipid bilayers K=440.7±160M(-1), while in an immobilized liposome layer K=35.53±3.53M(-1).
据报道，在溶液中存在乙酰胆碱和四丁基铵（TBA(+))时，将泛醌掺入支持的脂质双层和固定在金电极上的脂质体层中的还原动力学和热力学得到增强。通过循环伏安法确定的氧化还原反应的还原峰和半峰电位分别向正方向移动约 500 和 250 mV，在 TBA(+)的情况下；在乙酰胆碱的情况下，分别向正方向移动约 750 和 530 mV。信号强度随阳离子浓度变化，允许在毫摩尔范围内进行定量测定。据提议，泛醌的增强还原来自于形成四烷基铵阳离子-泛醌自由基阴离子离子对。电化学石英晶体微天平与耗散监测（EQCM-D）测量证实，电位偏移和氧化还原信号的强度与脂质膜上的四烷基铵阳离子的吸附相关。在生理 pH 值下，TBA(+)在脂质膜上的 Langmuir 吸附平衡常数（K）得以确定。在支持的脂质双层中，K=440.7±160M(-1)，而在固定化脂质体层中，K=35.53±3.53M(-1)。
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