title: Communication: Electronic UV-Vis transient spectra of the ∙OH reaction products of uracil, thymine, cytosine, and 5,6-dihydrouracil by using the complete active space self-consistent field second-order perturbation (CASPT2//CASSCF) theory.
abstract: Addition of ∙OH radicals to pyrimidine nucleobases is a common reaction in DNA/RNA damage by reactive oxygen species. Among several experimental techniques, transient absorption spectroscopy has been during the last decades used to characterize such compounds. Discrepancies have however appeared in the assignment of the adduct or adducts responsible for the reported transient absorption UV-Vis spectra. In order to get an accurate assignment of the transient spectra and a unified description of the absorption properties of the ∙OH reaction products of pyrimidines, a systematic complete active space self-consistent field second-order perturbation (CASPT2//CASSCF) theory study has been carried out on the uracil, thymine, and cytosine ∙OH addition adducts, as well as on the 5,6-dihydrouracil hydrogen abstraction products. With the obtained findings, the C5OH contributions to the lowest-energy band can be finally discarded. Instead, a bright (2)(π2) state of the C6OH adducts is determined to be the main responsible in all compounds for the absorption band in the Vis range.
authors: Instituto de Ciencia Molecular, Universitat de València, P.O. Box 22085, 46071 València, Spain.
authors: Antonio
authors: A
authors: Francés-Monerris
authors: Manuela
authors: M
authors: Merchán
authors: Daniel
authors: D
authors: Roca-Sanjuán
mesh_terms: D003596:Cytosine / Q000737:chemistry*; D004583:Electrons; D017665:Hydroxyl Radical / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D011789:Quantum Theory; D013056:Spectrophotometry, Ultraviolet; D013941:Thymine / Q000737:chemistry*; D014498:Uracil / Q000031:analogs & derivatives* / Q000737:chemistry*
chemical_list: C007419:dihydrouracil; D017665:Hydroxyl Radical; D014498:Uracil; D003596:Cytosine; D013941:Thymine