J Photochem Photobiol B. 1996 Jul;34(2-3):149-57. doi: 10.1016/1011-1344(95)07276-4.
The protective action of co-solutes, such as sucrose and glycinebetaine, against the thermal inactivation of photosystem II function was studied in untreated and Mn-depleted photosystem II preparations. It was shown that, in addition to the reactions that depend on the oxygen evolving activity of the photosystem, those that implicate more intimately the reaction center itself are protected by high concentrations of osmolytes. However, the temperature required to inhibit oxygen evolution totally in the presence of osmolytes is lower than that required to eliminate reactions, such as P680 (primary electron donor in photosystem II) photo-oxidation and pheophytin photo reduetion, which only involve charge separation and primary electron transport processes. The energy storage measured from the thermal dissipation yield during photoacoustic experiments and the yield of variable fluorescence are also protected to a significant degree (up to 30%) at temperatures at which oxygen evolution is totally inhibited. It is suggested that a cyclic electron transport reaction around photosystem II may be preserved under these conditions and may be responsible for the energy storage measured at relatively high temperatures. This interpretation is also supported by thermoluminescence data involving the recombination between reduced electron acceptors and oxidized electron donors at - 30 and - 55 °C. The data also imply that a high concentration of osmolyte allows the stabilization of the photosystem core complex together with the oxygen-evolving complex. The stabilization effect is understood in terms of the minimization of protein-water interactions as proposed by the theory of Arakawa and Timasheff (Biophys. J., 47 (1985) 411--414).
在未经处理和锰耗竭的光系统 II 制剂中，研究了共溶质（如蔗糖和甘氨酸甜菜碱）对光系统 II 功能热失活的保护作用。结果表明，除了依赖于光系统放氧活性的反应外，那些更密切涉及反应中心本身的反应也受到高浓度渗透物的保护。然而，在存在渗透物的情况下完全抑制氧合所需的温度低于消除反应所需的温度，例如 P680（光系统 II 中的初级电子供体）光氧化和叶绿素光还原，这些反应仅涉及电荷分离和初级电子传递过程。在光声实验中从热耗散产额测量的能量储存和可变荧光产额也在氧合完全抑制的温度下受到显著保护（高达 30%）。有人建议，在这些条件下可能会保留光系统 II 周围的循环电子传递反应，并且可能是在相对较高温度下测量的能量储存的原因。该解释也得到了涉及在-30 和-55°C 下还原电子受体和氧化电子供体之间复合的热致发光数据的支持。这些数据还意味着高浓度的渗透物允许与放氧复合物一起稳定光系统核心复合物。稳定效应是根据 Arakawa 和 Timasheff（Biophys. J.，47（1985）411-414）理论提出的最小化蛋白质-水相互作用来理解的。
