Zhang S, Xie J, Zhang J, Zhao J, Jiang L
Institute of Photographic Chemistry, Academia Sinica, Beijing 100101, People's Republic of China.
Biochim Biophys Acta. 1999 Jan 4;1426(1):205-11. doi: 10.1016/s0304-4165(98)00153-6.
Visible light (>470 nm) irradiation of an oxygen-saturated solution of C-phycocyanin (C-PC) in the presence of the spin trap 5, 5-dimethyl-1-pyrroline-N-oxide (DMPO) gave an ESR spectrum characteristic of the DMPO-hydroxyl radical spin adduct DMPO-OH. The signal intensities of DMPO-OH adduct were enhanced by superoxide dismutase (SOD) and partly inhibited by catalase. It was partly responsible for the production of DMPO-OH that superoxide anion radical (O.-2) dismutated to generate hydrogen peroxide (H2O2) which decomposed ultimately to generate the highly reactive .OH. In addition, it can be concluded that singlet oxygen (1O2) was an important intermediate according to the strong inhibitory action of 1,4-diazabicyclo[2.2.2]octane (DABCO) and histidine on DMPO-OH formation. The experimental results suggest that photodynamic action of C-PC proceed via both type I and type II mechanisms. Furthermore, the decay kinetics of DMPO-OH adduct, the effects of DMPO and C-PC concentrations as well as irradiation time on DMPO-OH adduct formation were also discussed. Concentration of C-PC should be an important factor to influence the ESR signal intensities of DMPO-OH. Therefore, it may be concluded that reasonably lower concentration of C-PC might prolong the duration of photosensitized formation of .OH and might strengthen the photodynamic action.
在自旋捕获剂5,5-二甲基-1-吡咯啉-N-氧化物（DMPO）存在下，用可见光（>470 nm）照射氧饱和的藻蓝蛋白（C-PC）溶液，得到了DMPO-羟基自由基自旋加合物DMPO-OH的特征电子自旋共振（ESR）谱。超氧化物歧化酶（SOD）增强了DMPO-OH加合物的信号强度，而过氧化氢酶则部分抑制了该信号强度。超氧阴离子自由基（O₂⁻）歧化生成过氧化氢（H₂O₂），H₂O₂最终分解生成高活性的·OH，这在一定程度上导致了DMPO-OH的产生。此外，根据1,4-二氮杂双环[2.2.2]辛烷（DABCO）和组氨酸对DMPO-OH形成的强烈抑制作用，可以得出单线态氧（¹O₂）是一个重要中间体的结论。实验结果表明，C-PC的光动力作用通过I型和II型机制进行。此外，还讨论了DMPO-OH加合物的衰减动力学、DMPO和C-PC浓度以及照射时间对DMPO-OH加合物形成的影响。C-PC的浓度应该是影响DMPO-OH的ESR信号强度的一个重要因素。因此，可以得出结论，适当降低C-PC的浓度可能会延长·OH光敏形成的持续时间，并可能增强光动力作用。
