Chatterjee S R, Shetty S J, Devasagayam T P, Srivastava T S
Department of Chemistry, Indian Institute of Technology, Bombay, Powai, India.
J Photochem Photobiol B. 1997 Nov;41(1-2):128-35. doi: 10.1016/s1011-1344(97)00094-8.
meso-Tetrakis[4-(carboxymethyleneoxy)phenyl]porphyrin (H2T4CPP) cleaves pBR322 plasmid DNA to single strand breaks in the presence of molecular oxygen and visible light. The above photocleavage was much more efficient in D2O buffer of sodium phosphate (pD = 7.4) than H2O buffer of sodium phosphate (pH = 7.4). In addition this photocleavage of plasmid DNA was inhibited in the presence of sodium azide, lipoic acid, tert-butanol or mannitol suggesting the involvement of 1O2 and.OH in the photocleavage of plasmid DNA. The photocleavage was observed to be more efficient in the presence of H2T4CPP than in the presence of H2CPP [meso-tetrakis (4-carboxy-phenyl)porphyrin]. Our spectral studies using UV-visible, fluorescence and circular dichroism techniques suggest that H2T4CPP binds to DNA while H2CPP does not. Thus, the difference in photocleavage may be caused by the nonbinding of H2CPP and by the binding of H2T4CPP to calf thymus (CT) DNA.
中位-四[4-(羧基亚甲基氧基)苯基]卟啉(H2T4CPP)在分子氧和可见光存在下可将pBR322质粒DNA切割成单链断裂。上述光切割在磷酸钠的重水溶液缓冲液(pD = 7.4)中比磷酸钠的水溶液缓冲液(pH = 7.4)中效率高得多。此外，在叠氮化钠、硫辛酸、叔丁醇或甘露醇存在下，质粒DNA的这种光切割受到抑制，这表明单线态氧(1O2)和羟基自由基(·OH)参与了质粒DNA的光切割过程。观察到在H2T4CPP存在下的光切割比在H2CPP[中位-四(4-羧基苯基)卟啉]存在下更有效。我们使用紫外-可见光谱、荧光光谱和圆二色光谱技术进行的光谱研究表明，H2T4CPP与DNA结合，而H2CPP不与DNA结合。因此，光切割的差异可能是由H2CPP不结合以及H2T4CPP与小牛胸腺(CT)DNA结合所致。
