Balasubramanian B, Pogozelski W K, Tullius T D
Department of Pathology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Proc Natl Acad Sci U S A. 1998 Aug 18;95(17):9738-43. doi: 10.1073/pnas.95.17.9738.
Despite extensive study, there is little experimental information available as to which of the deoxyribose hydrogen atoms of duplex DNA reacts most with the hydroxyl radical. To investigate this question, we prepared a set of double-stranded DNA molecules in which deuterium had been incorporated specifically at each position in the deoxyribose of one of the four nucleotides. We then measured deuterium kinetic isotope effects on the rate of cleavage of DNA by the hydroxyl radical. These experiments demonstrate that the hydroxyl radical reacts with the various hydrogen atoms of the deoxyribose in the order 5' H > 4' H > 3' H approximately 2' H approximately 1' H. This order of reactivity parallels the exposure to solvent of the deoxyribose hydrogens. Our work therefore reveals the structural basis of the reaction of the hydroxyl radical with DNA. These results also provide information on the mechanism of DNA damage caused by ionizing radiation as well as atomic-level detail for the interpretation of hydroxyl radical footprints of DNA-protein complexes and chemical probe experiments on the structure of RNA and DNA in solution.
尽管进行了广泛的研究，但关于双链DNA的脱氧核糖氢原子中哪一个与羟基自由基反应最强烈，目前几乎没有实验信息。为了研究这个问题，我们制备了一组双链DNA分子，其中氘被特异性地掺入到四个核苷酸之一的脱氧核糖的每个位置。然后，我们测量了氘动力学同位素效应，以研究羟基自由基对DNA切割速率的影响。这些实验表明，羟基自由基与脱氧核糖的各种氢原子的反应顺序为5'H > 4'H > 3'H ≈ 2'H ≈ 1'H。这种反应活性顺序与脱氧核糖氢原子暴露于溶剂的程度相似。因此，我们的工作揭示了羟基自由基与DNA反应的结构基础。这些结果还为电离辐射引起的DNA损伤机制提供了信息，以及为解释DNA-蛋白质复合物的羟基自由基足迹和溶液中RNA和DNA结构的化学探针实验提供了原子水平的细节。
