Products of Thymine Oxygenation by a Non-heme Oxygenation Model, Fe<sup>II</sup>(MeCN)<sub>6</sub><sup>2+</sup>&ndash;Ac<sub>2</sub>O&ndash;H<sub>2</sub>O<sub>2</sub>, and the Transition State Model between Oxoiron and Thymine
作者:Shigeki Kobayashi、Akihiko Takagi、Toshiyuki Chikuma、Osamu Tamura、Eiichi Kotani、Takao Katase
DOI:10.1248/cpb.58.775
日期:——
Oxidative thymine damage was investigated using a new non-heme oxygenation model, Fe(MeCN)62+–H2O2–Ac2O, based on high-spin Fe(MeCN)62+ in a non-aqueous solution, Ac2O–MeCN. Thymine and 1,3-dimethylthymine oxidized by the system gave the corresponding trans-thymine glycol derivatives in good yield. Thymineglycol is equivalent to an oxidative product as a measure of oxidative DNA damage in living cells. It is suggested that the activation of Fe(MeCN)62+–H2O2–Ac2O in Ac2O–MeCN forms the oxoiron O=FeIV(AcO)(MeCN)4+ as an active species via a hetelolytic two-electron mechanism, not a Haber–Weiss–Fenton-type reaction with a one-electron process by treatment with a radical scavenger. In addition, we also demonstrated the transition state (TS) for the interaction between thymine and O=FeIV(AcO)(MeCN)4+ in the triplet spin (spin multiplicity; M=3). This model of oxidative thymine damage may provide new insight into the oxidative mechanism of thymine glycol production in non-aqueous reactions of thymine.
利用一种新的非血红素氧化模型,即基于非水溶液Ac2O-MeCN中的高自旋Fe(MeCN)6^2+的Fe(MeCN)6^2+-H2O2-Ac2O体系,研究了胸腺嘧啶的氧化损伤。在该体系中,胸腺嘧啶和1,3-二甲基胸腺嘧啶被氧化生成相应的反式胸腺嘧啶二醇衍生物,产率良好。胸腺嘧啶二醇相当于一种氧化产物,可作为活细胞中氧化DNA损伤的衡量标准。研究表明,在Ac2O-MeCN中Fe(MeCN)6^2+-H2O2-Ac2O的活化通过异裂双电子机制形成活性物种O=FeIV(AcO)(MeCN)4+,而不是通过自由基清除剂处理时的Haber-Weiss-Fenton型单电子反应。此外,我们还阐明了胸腺嘧啶与O=FeIV(AcO)(MeCN)4+在三重态自旋(自旋多重性;M=3)中的相互作用过渡态(TS)。这一胸腺嘧啶氧化损伤模型可能为胸腺嘧啶在非水反应中生成胸腺嘧啶二醇的氧化机制提供新的见解。