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Characteristics of the Excited Triplet States of Thiolated Guanosine Derivatives and Singlet Oxygen Generation

Miyata, Shoma; Tanabe, Shunsuke; Isozaki, Tasuku; Xu, Yao-Zhong and Suzuki, Tadashi (2018). Characteristics of the Excited Triplet States of Thiolated Guanosine Derivatives and Singlet Oxygen Generation. Photochemical & Photobiological Sciences, 17(10) pp. 1469–1476.

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Thioguanine is sensitive to UVA light and generates singlet molecular oxygen (1O2*) when exposed to UVA. Three thioguanosine derivatives, 2’,3’,5’–tri–O–acetyl–6–thioguanosine (ta6TGuo), 2’,3’,5’–tri–O–acetyl–8–thioguanosine (ta8TGuo), and 2’,3’,5’–tri–O–acetyl–6,8–dithioguanosine (taDTGuo) were explored photophysically and photochemically. The nanosecond transient absorption and time–resolved near–infrared emission measurements were carried out to investigate the characteristics of their excited triplet states in acetonitrile solution. The quantum yield of intersystem crossing (∅ISC), the intrinsic decay rate constant (k0), the quenching rate constant by 3O2 (kq) and the self–quenching rate constant (kSQ) of their triplet states were all determined. From precise analysis of the quantum yield of 1O2* generation (∅Δ) against the concentration of dissolved molecular oxygen, the fraction of the triplet states quenched by dissolved oxygen which gives rise to 1O2* formation (SΔ) was successfully obtained with high accuracy. The ∅Δ values at low oxygen concentrations reveal these thioguanosines, particularly taDTGuo, can still effectively generate 1O2* under low molecular oxygen concentration like carcinomatous microenvironments. These findings indicate that taDTGuo would perform well as a potential agent for photo–induced cancer therapies.

Item Type: Journal Item
Copyright Holders: 2018 The Royal Society of Chemistry and Owner Societies
ISSN: 1474-9092
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Life, Health and Chemical Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Research Group: eSTEeM
Item ID: 56726
Depositing User: Yao Xu
Date Deposited: 25 Sep 2018 15:51
Last Modified: 16 Jun 2020 23:04
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