Photoionization of Organic Phosphates by 193 nm Laser Light in Aqueous Solution: Rapid Intramolecular H-Transfer to the Primarily Formed Phosphate Radical. A Model for Ionization-Induced Chain-Breakage in DNA?
作者:Steen Steenken、Ludmila Goldbergerova
DOI:10.1021/ja974393m
日期:1998.4.1
phosphates such as ribose-5-phosphate leads to ionization with formation of the corresponding oxygen-centered phosphate radicals, O3PO•. These (oxidizing) radicals function as traps with respect to hydrogens attached to α-, β-, or, possibly, γ-carbons, whereby in the case of the β-hydrogens a six-membered transition state for transfer of the hydrogen to the phosphate oxygen is possible, leading to high rate
在水溶液中,193 nm (6.4 eV) 无机和有机磷酸盐(如 5-磷酸核糖)的光解导致电离,形成相应的以氧为中心的磷酸根 O3PO•。这些(氧化)自由基对于连接到 α-、β- 或可能的 γ-碳上的氢起到陷阱的作用,其中在 β-氢的情况下,六元过渡态用于将氢转移到磷酸氧是可能的,导致这些单分子反应中氢转移的高速率常数(高达> 5 × 107 s-1)。在(脱氧)核糖磷酸酯的情况下,六元过渡态有可能将 C4 的氢转移到 C5 和 C3 的磷酸基团。在 DNA 中,由此产生的 C4'-自由基将经历磷酸酯基团的快速β-消除,这一步代表 DNA 链断裂。显然很容易从碳到磷酸根的 H 转移,这些自由基被“修复”,这就是为什么磷酸根不...