R-藻红蛋白介导的光敏反应对DNA分子的生物学效应

藻红蛋白(phycoerythrin, PE)是海藻中的重要捕光色素蛋白，具有强荧光性，易溶于水.在藻体内能将捕获的光能传递给光合反应中心; 在体外则能将光能传递给周围环境中的氧分子，产生如单线态氧等活性氧组分，可用来介导光动力效应治疗癌症.将纯化的藻红蛋白加入到瘤细胞培养基中，数小时后，采用488 nm波长的氩离子激光辐照，MTT法检测细胞存活数，计算细胞存活率. ³H-TdR掺入实验观察细胞DNA的合成.结果表明，藻红蛋白介导的光动力反应能够有效地抑制肿瘤细胞DNA合成并杀伤癌细胞.随着藻红蛋白浓度增加，DNA合成下降，瘤细胞存活率降低.将藻红蛋白加入到pUC18质粒溶液中，随之进行激光辐照，琼脂糖电泳结果可见pUC18构象由超螺旋（supercoiled）向带切口的环形构象(relax)转换.结果提示：通过改变或影响DNA构象，抑制细胞DNA合成可能是藻红蛋白介导肿瘤光动力治疗的途径之一.

Biological Effect of R-Phycoerythrin-mediated Photosensitization on DNA

R-phycoerythrin(R-PE) is one of important proteins involved in capturing light during photosynthesis in red algae, and it is highly fluorescent, and water-soluble chromophores. In vivo, it can transfer the light energy into photosynthetic center, however, it can deliver the captured light energy captured to the surrounding oxygen in vitro and produce reactive oxygen species such as singlet oxygen, which is toxic to tumor cells. R-PE was added to the culture medium of tumor cells, subsequently with irradiation of 488 nm, Argon laser of 25.6 J/cm². The result by MTT assay showed that the survival rate decreased with the increase of R-PE concentration from 1 to 100 mg/L. The result from ³H-TdR incorporation demonstrated that the synthesis of DNA reduced when the concentration of R-PE increased from 0.01 to 0.32 mg/L. Besides, pUC18 DNA showed a conversion from supercoiled into linear conformation. The conclusion comes that R-PE mediated PDT can influence the conformation of DNA, and it may be one of the mechanisms of R-PE mediated photodynamic therapy .