Formation of oxidative photoproduct of tri-acetyl-modified 6-thioguanosine by UVA irradiation

Miyata, Shoma; Aoki, Ui; Tanabe, Shunsuke; Isozaki, Tasuku; Xu, Yao-Zhong. and Suzuki, Tadashi (2018). Formation of oxidative photoproduct of tri-acetyl-modified 6-thioguanosine by UVA irradiation. Photomedicine and photobiology, 39 pp. 15–18.

Abstract

Thio-substituted nucleobases such as 6-thioguanine are known to be photosensitive to UVA light and capable of generating singlet molecular oxygen (1O2*). 2’,3 ’,5 ’- Tri-O-acetyl-6-thioguanosine (ta6TGuo) was prepared and its photochemistry was investigated. ta6TGuo in the aerated acetonitrile solution under UVA irradiation generates 1O2* that can also oxidize ta6TGuo itself and finally convert into tri-acetylated guanosine sulfonate (taGuoSO3). The decay rate constant of ta6TGuo was found to be in good agreement with the formation rate constant of taGuoSO3, revealing that the first step in the reaction of ta6TGuo with 1O2* would be the rate-determining step in forming taGuoSO3 as the final product. Thiolated nucleosides such as 6-thioguanosine could be used as a photosensitive agent for light-induced therapies. The key feature in the UVA irradiation of the thionucleosideis to produce 1O2*, but the resultant oxidative products would also contribute to the effect on therapies.

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