A B3LYP Study on Repair of Guanyl and 8-Oxoguanyl Radical by Simultaneous Proton- and Electron-Transfer Reaction

• Published in: Bulletin of the Chemical Society of Japan Vol. 84; no. 2; pp. 181 - 190
• Main Authors: Yamamura, Mami, Ichino, Tomoya, Yoshioka, Yasunori
• Format: Journal Article
• Language: English
• Published: Tokyo The Chemical Society of Japan 15-02-2011; Chemical Society of Japan
• ISSN: 0009-2673; 1348-0634
• DOI: 10.1246/bcsj.20100211

The proton transfers in base pairs of guanine (G)/8-oxoguanine (8G), 8G+•–C, PhOH–G(-H)•, PhOH–8G(-H)•, and 8G–G(-H)•, have been theoretically examined in the gas phase at the B3LYP level of theory. For the 8G+•–C base pair, the single proton transfer proceeds from N1(8G+•) to N3(C) with the activation energy of 2.2 kcal mol−1. The repairs of G(-H)• and 8G(-H)• bases to G and 8G have been studied by reaction with phenol, and the repair of G(-H)• base has been also studied for the pair with the 8G base. These three reactions proceed under the PCET mechanism, in which the proton transfers through the σ-path, while the electron transfers through the π-path. For reactions with PhO• and G(-H)•, 8G easily delivers a proton and electron to yield PhOH and G. It is expected that 8G functions to protect other bases and amino acids from oxidation.