Attenuation of guanine oxidation via DNA-mediated electron transfer in a crowded environment using small cosolutes

Abstract

Guanine oxidation induced by photoirradiation on a pyrene-modified oligonucleotide was investigated under molecular crowding using small cosolutes such as glycerol. The efficiency of guanine photooxidation was suppressed in accordance with the increase in the concentration of glycerol. The results of photooxidation experiments using fully matched and mismatched DNA showed that guanine decomposition was mainly caused by DNA-mediated electron transfer (ET) in glycerol mixed solutions, as well as in diluted aqueous buffer solutions. Multiple factors can contribute to the suppression of guanine oxidation in crowded environments. However, our experimental results indicated that the attenuation of the DNA-mediated ET process suppressed guanine oxidation. On the other hand, experiments using ethylene glycol showed that the guanine decomposition efficiency varies depending on the surrounding solvent. These results suggested that changes in the characteristics of the surrounding medium affect the DNA fluctuation, dominating DNA-mediated ET.