Comparative studies of AOT and NaDEHP by fluorescence technique and z-potential (ζ) measurements

The aggregation behaviors of two surfactants with the same hydrophobic tail, sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and sodium bis(2-ethylhexyl)phosphate (NaDEHP), have been investigated by the fluorescence technique and z-potential (ζ) measurements. Five fine peaks of the pyrene molecule fluorescence spectroscopy appear in the surfactant solution, and the micropolarity at which pyrene locates is monitored from the intensity ratio of the first (I1) and the third peak (I3). A wide peak around 475 nm, the emission spectra of the excimer of pyrene molecules, is observed in the NaDEHP solution, while this is not found for the AOT system. The value of I1/I3 decreases in a more limited concentration range for the AOT system than for NaDEHP, indicating that small aggregates can be more easily formed by NaDEHP molecules. The z-potential results for the aggregates formed by the two surfactants show that the interaction between AOT and PVP is stronger than that between NaDEHP and PVP.

甘油和蔗糖对光系统I结构与功能的影响

在光系统I(PSI)内部结合有大量的水分子，而这些水分子的生理功能还不清楚。在本工作中，我们通过外加具有渗透活性和吸水强的多羟基化合物甘油和蔗糖来改变PSI环境中水的含量，研究水的改变对PSI结构与功能的影响。主要结果如下： 1．甘油和蔗糖对PSI的电子传递产生影响，影响程度和大小与它们的浓度有关。一般地，低浓度的甘油和蔗糖可促进PSI的电子传递，而在高浓度时，这种促进作用有所减弱。但过高浓度的甘油(>60%, v/v)会抑制PSI的电子传递活性。 2．与对PSI电子传递的影响趋势相类似，在低浓度的甘油和蔗糖存在下，PSI的光化学反应活性(PSI反应中心色素P700的光氧化还原能力)大为增加，而较高浓度的甘油和蔗糖对P700的氧化还原能力有所抑制。 3．甘油和蔗糖也会改变PSI中的主体色素(bulk chlorophyll)和长波色素或红色素(red chlorophyll)之间的能量分布。它们的作用导致激发能分配失衡，使更多的激发能分配到红色素。 4．甘油和蔗糖的作用还会影响PSI的蛋白质构象。甘油使PSI蛋白质内部的色氨酸残基(Trpapolar)处于更加疏水的微环境，而蔗糖却使极性环境中的色氨酸残基(Trppolar)周围微环境的极性继续增大。它们均会使色氨酸残基邻近的具有淬灭活性的蛋白质的位置和/或方向有所变化。同时，甘油和蔗糖的作用也会导致PSI的疏水性增加。