CEDEME, Universidade Federal de São Paulo, São Paulo, Brazil.
Spectrochim Acta A Mol Biomol Spectrosc. 2010 Nov;77(4):908-10. doi: 10.1016/j.saa.2010.07.008. Epub 2010 Jul 18.
In mammalian cells, DNA-bound Fe(II) reacts with H₂O₂ producing the highly reactive hydroxyl radical (OH) in situ. Since ·OH attacks nearby DNA residue generating oxidative DNA damage, many questions have arisen regarding iron-DNA complex formations and their implication in pre-malignant mutations and aging. In this work, a solid sample of Fe(II)-DNA complex containing one Fe(II) per 10 nucleotides was analyzed from extended X-ray absorption fine structure (EXAFS) spectra collected in a synchrotron radiation light source. Best fitting parameters of the EXAFS signal for the first two shells provide evidence of five oxygen atoms at 1.99 ± 0.02 Å and one nitrogen atom at 2.20 ± 0.02 Å in the inner coordination sphere of the Fe(II)-DNA complex. Considering that both purine base moieties bearing nitrogen atoms are prone to chelate iron, these results are consistent with the previously observed lower levels of DNA damage in cytosine nucleotides relative to adenine and guanine sites in cells under more physiological conditions of Fe(II) Fenton reaction.
在哺乳动物细胞中，与 DNA 结合的 Fe(II) 与 H₂O₂ 反应，就地生成高反应性的羟基自由基 (OH)。由于·OH 攻击附近的 DNA 残基，产生氧化 DNA 损伤，因此出现了许多关于铁-DNA 配合物形成及其在癌前突变和衰老中的意义的问题。在这项工作中，从在同步辐射光源中收集的扩展 X 射线吸收精细结构 (EXAFS) 光谱中分析了含有每 10 个核苷酸一个 Fe(II) 的 Fe(II)-DNA 配合物的固体样品。对于前两个壳层的 EXAFS 信号的最佳拟合参数提供了证据，表明在 Fe(II)-DNA 配合物的内配位球中存在 5 个氧原子，在 1.99 ± 0.02 Å 和 1 个氮原子，在 2.20 ± 0.02 Å。考虑到带有氮原子的嘌呤碱基部分都容易螯合铁，这些结果与在更生理条件下的 Fenton 反应中，Fe(II) 下细胞中胞嘧啶核苷酸相对于腺嘌呤和鸟嘌呤位点的 DNA 损伤水平较低的先前观察结果一致。
