title: Thymidine radical formation via one-electron transfer oxidation photoinduced by pterin: Mechanism and products characterization.
abstract: UV-A radiation (320-400nm), recognized as a class I carcinogen, induces damage to the DNA molecule and its components through different mechanisms. Pterin derivatives are involved in various biological functions, including enzymatic processes, and it has been demonstrated that oxidized pterins may act as photosensitizers. In particular, they accumulate in the skin of patients suffering from vitiligo, a chronic depigmentation disorder. We have investigated the ability of pterin (Ptr), the parent compound of oxidized pterins, to photosensitize the degradation of the pyrimidine nucleotide thymidine 5'-monophosphate (dTMP) in aqueous solutions under UV-A irradiation. Although thymine is less reactive than purine nucleobases, our results showed that Ptr is able to photoinduce the degradation of dTMP and that the process is initiated by an electron transfer from the nucleotide to the triplet excited state of Ptr. In the presence of molecular oxygen, the photochemical process leads to the oxidation of dTMP, whereas Ptr is not consumed. In the absence of oxygen, both compounds are consumed to yield a product in which the pterin moiety is covalently linked to the thymine. This compound retains some of the spectroscopic properties of Ptr, such as absorbance in the UV-A region and fluorescence properties.
authors.affiliation: Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata (UNLP), CCT La Plata-CONICET, Diagonal 113 y 64, 1900 La Plata, Argentina.
authors.forename: Mariana P
authors.initials: MP
authors.lastname: Serrano
authors.affiliation: Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata (UNLP), CCT La Plata-CONICET, Diagonal 113 y 64, 1900 La Plata, Argentina.
authors.forename: Mariana
authors.initials: M
authors.lastname: Vignoni
authors.affiliation: Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata (UNLP), CCT La Plata-CONICET, Diagonal 113 y 64, 1900 La Plata, Argentina.
authors.forename: Carolina
authors.initials: C
authors.lastname: Lorente
authors.affiliation: Laboratoire des Interactions Moléculaires et Réactivité Chimique et Photochimique (IMRCP), UMR 5623-CNRS/UPS, Université Toulouse III (Paul Sabatier), 118, route de Narbonne, F-31062 Toulouse cédex 9, France.
authors.forename: Patricia
authors.initials: P
authors.lastname: Vicendo
authors.affiliation: Laboratoire des Interactions Moléculaires et Réactivité Chimique et Photochimique (IMRCP), UMR 5623-CNRS/UPS, Université Toulouse III (Paul Sabatier), 118, route de Narbonne, F-31062 Toulouse cédex 9, France.
authors.forename: Esther
authors.initials: E
authors.lastname: Oliveros
authors.affiliation: Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata (UNLP), CCT La Plata-CONICET, Diagonal 113 y 64, 1900 La Plata, Argentina. Electronic address: athomas@inifta.unlp.edu.ar.
authors.forename: Andrés H
authors.initials: AH
authors.lastname: Thomas
mesh_terms: D004579:Electron Transport / Q000187:drug effects; D006801:Humans; D010084:Oxidation-Reduction / Q000187:drug effects*; D010100:Oxygen / Q000737:chemistry; D017319:Photosensitizing Agents / Q000494:pharmacology*; D011622:Pterins / Q000494:pharmacology*; D011685:Purine Nucleotides / Q000737:chemistry; D013938:Thymidine Monophosphate / Q000737:chemistry* / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D017319:Photosensitizing Agents; D011622:Pterins; D011685:Purine Nucleotides; D013938:Thymidine Monophosphate; D010100:Oxygen
keywords: Photosensitization; Pterins; Thymine; Type I photooxidation