Kagan J, Chen X, Wang T P, Forlot P
Department of Chemistry, University of Illinois, Chicago 60680.
Photochem Photobiol. 1992 Aug;56(2):185-93. doi: 10.1111/j.1751-1097.1992.tb02146.x.
Supercoiled (SC) pBR322 was used to probe the recent claim that 5-geranoxylpsoralen (5-GOP) did not photoreact with DNA. Contrary to expectations, 5-GOP was found to damage DNA in the presence of UV-A through two competing pathways: (a) single strand breaks, identified by the conversion of supercoiled into open circular and linear DNA, and (b) cross-linking, revealed by the fluence-dependent decrease in the extent of denaturation of the double stranded supercoiled DNA to single stranded circular DNA. In addition, a fluence-dependent modification reduced the ability of the restriction enzyme EcoR I to linearize the photosensitized DNA, and alkali-labile lesions were generated. Psoralen, 5-methoxypsoralen, and 8-methoxypsoralen, which are well-known to undergo cycloaddition to DNA, had a more pronounced effect on supercoiled DNA. Single strand breaks occurred more readily than with 5-GOP, and the surviving SC form remaining had reduced electrophoretic mobility in agarose gels. In all cases, the DNA damage was more prominent when oxygen was absent.
超螺旋（SC）pBR322被用于探究最近关于5-香叶氧基补骨脂素（5-GOP）不与DNA发生光反应的说法。与预期相反，发现5-GOP在紫外线A存在的情况下通过两条相互竞争的途径损伤DNA：（a）单链断裂，通过超螺旋DNA转变为开环和线性DNA来鉴定；（b）交联，通过双链超螺旋DNA变性为单链环状DNA的程度随光通量的依赖性降低来揭示。此外，光通量依赖性修饰降低了限制性内切酶EcoR I使光敏化DNA线性化的能力，并产生了碱不稳定损伤。众所周知会与DNA发生环加成反应的补骨脂素、5-甲氧基补骨脂素和8-甲氧基补骨脂素对超螺旋DNA有更显著的影响。单链断裂比5-GOP更容易发生，剩余的存活超螺旋形式在琼脂糖凝胶中的电泳迁移率降低。在所有情况下，无氧时DNA损伤更明显。
