Yoakum G H, Cole R S
Biochim Biophys Acta. 1978 Dec 21;521(2):529-46. doi: 10.1016/0005-2787(78)90295-2.
Photoreaction of 4,5',8-trimethylpsoralen with superhelical ColE1 and ColE1amp DNA was studied. Changes in mobilities in agarose gels, formation of interstrand cross-links, and DNA strand breaks were determined. Psoralen and light treatment removed negative superhelical turns, and extensive treatments failed to produce positive superhelical turns in covalently closed plasmid DNA. The rate of relaxation of superhelical turns by psoralen Photobinding appeared to be directly proportional to the number of superhelical turns remaining. A unique reaction mechanism is presented to explain these results. By this interpretation the initial rate of psoralen photobinding to superhelical DNA was estimated to be 3 times that for linear DNA, and the ratio of cross-linking to monofuctional adducts appears to be dependent on the superhelical conformation of the DNA. The estimated ratio of psoralen molecules bound to DNA strand breaks was 1.7 . 10(4):1, and 70% of this breakage is caused by the light alone.
研究了4,5',8-三甲基补骨脂素与超螺旋ColE1和ColE1amp DNA的光反应。测定了琼脂糖凝胶中迁移率的变化、链间交联的形成以及DNA链断裂情况。补骨脂素和光处理消除了负超螺旋圈，而大量处理未能在共价闭合的质粒DNA中产生正超螺旋圈。补骨脂素光结合使超螺旋圈松弛的速率似乎与剩余超螺旋圈的数量成正比。提出了一种独特的反应机制来解释这些结果。根据这种解释，补骨脂素光结合到超螺旋DNA的初始速率估计是线性DNA的3倍，交联与单功能加合物的比例似乎取决于DNA的超螺旋构象。补骨脂素分子与DNA链断裂的估计比例为1.7×10⁴:1，其中70%的断裂仅由光引起。
