Acta Phys. -Chim. Sin. ›› 2008, Vol. 24 ›› Issue (02): 269-274.doi: 10.3866/PKU.WHXB20080215

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Ring-Opening Reaction Mechanism of 8-Hydroxyguanine Radical

HOU Ruo-Bing; LI Wei-Wei; SHEN Xing-Can   

  1. School of Chemistry and Chemical Engineering, Guangxi Normal University, Guilin 541004, Guangxi Province, P. R. China
  • Received:2007-08-07 Revised:2007-10-12 Published:2008-01-26
  • Contact: HOU Ruo-Bing

Abstract: The theoretical studies on the mechanisms of ring-opening reaction of 8-hydroxyguanine radical were performed by the experimentally calibrated theoretical method of B3LYP/DZP++. All of the computational results revealed that the ring-opening reaction occured through a pathway including two elementary reactions, the C8—N9 bond-broken step followed by a transfer step of cation-like hydrogen atom of the hydroxyl moiety. The high activation energy in the transfer reaction of hydrogen atom in the absence of water led this reaction to be somewhat difficult; on the contrary, the hydrogen transfer might occur feasibly with assistance of one water molecule due to the formation of a six-member ring transition state which was beneficial to lower the reaction activation energy. The difference of the activation energies of two elementary reactions demonstrated that the rate-limiting steps of ring-opening reaction in the absence of water and in the presence of water were the hydrogen transfer step and C8—N9 bond-broken process, respectively.

Key words: 8-Hydroxyguanine radical, Ring-opening reaction, H-transfer reaction, Catalytic action of water