Photophysical and photochemical properties of 4-thiouracil: time-resolved IR spectroscopy and DFT studies.
Xiaoran Zou, Xiaojuan Dai, Kunhui Liu, Hongmei Zhao, Di Song, Hongmei Su
Index: J. Phys. Chem. B 118(22) , 5864-72, (2014)
Full Text: HTML
Abstract
Intensified research interests are posed with the thionucleobase 4-thiouracil (4-TU), due to its important biological function as site-specific photoprobe to detect RNA structures and nucleic acid-nucleic acid contacts. By means of time-resolved IR spectroscopy and density functional theory (DFT) studies, we have examined the unique photophysical and photochemical properties of 4-TU. It is shown that 4-TU absorbs UVA light and results in the triplet formation with a high quantum yield (0.9). Under N2-saturated anaerobic conditions, the reactive triplet undergoes mainly cross-linking, leading to the (5-4)/(6-4) pyrimidine-pyrimidone product. In the presence of O2 under aerobic conditions, the triplet 4-TU acts as an energy donor to produce singlet oxygen (1)O2 by triplet-triplet energy transfer. The highly reactive oxygen species (1)O2 then reacts readily with 4-TU, leading to the products of uracil (U) with a yield of 0.2 and uracil-6-sulfonate (U(SO3)) that is fluorescent at ~390 nm. The product formation pathways and product distribution are well rationalized by the joint B3LYP/6-311+G(d,p) calculations. From dynamics and mechanistic point of views, these results enable a further understanding for 4-TU acting as reactive precursors for photochemical reactions relevant to (1)O2, which has profound implications for photo cross-linking, DNA photodamage, as well as photodynamic therapy studies.
Related Compounds
Related Articles:
1999-02-01
[RNA 5(2) , 318-29, (1999)]
Photoelectron spectroscopic study of the negative ions of 4-thiouracil and 2,4-dithiouracil.
2011-02-21
[J. Chem. Phys. 134(7) , 074304, (2011)]
2014-01-01
[Photochem. Photobiol. Sci. 10(8) , 1294-302, (2011)]
2013-10-11
[J. Biol. Chem. 288(41) , 29954-64, (2013)]
Structure and tautomerism of the neutral and monoanionic forms of 4-thiouracil derivatives.
1974-10-30
[J. Am. Chem. Soc. 96(22) , 6832-9, (1974)]