title: Unraveling the Degradation Mechanism of Purine Nucleotides Photosensitized by Pterins: The Role of Charge-Transfer Steps.
abstract: Photosensitized reactions contribute to the development of skin cancer and are used in many applications. Photosensitizers can act through different mechanisms. It is currently accepted that if the photosensitizer generates singlet molecular oxygen ((1) O2 ) upon irradiation, the target molecule can undergo oxidation by this reactive oxygen species and the reaction needs dissolved O2 to proceed, therefore the reaction is classified as (1) O2 -mediated oxidation (type II mechanism). However, this assumption is not always correct, and as an example, a study on the degradation of 2'-deoxyguanosine 5'-monophosphate photosensitized by pterin is presented. A general mechanism is proposed to explain how the degradation of biological targets, such as nucleotides, photosensitized by pterins, naturally occurring (1) O2 photosensitizers, takes place through an electron-transfer-initiated process (type I mechanism), whereas the contribution of the (1) O2 -mediated oxidation is almost negligible.
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, Casilla de Correo 16, Sucursal 4, (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, Casilla de Correo 16, Sucursal 4, (1900) La Plata (Argentina).
authors.forename: Carolina
authors.initials: C
authors.lastname: Lorente
authors.affiliation: Laboratorio de Cinética y Fotoquímica (LACIFO), Centro de Investigaciones y Transferencia de Santiago del Estero (CITSE-CONICET) Universidad Nacional de Santiago del Estero (UNSE), Casilla de Correo 23, Bs. As. 252, G4200AQF, Santiago del Estero (Argentina).
authors.forename: Claudio D
authors.initials: CD
authors.lastname: Borsarelli
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, Casilla de Correo 16, Sucursal 4, (1900) La Plata (Argentina). athomas@inifta.unlp.edu.ar.
authors.forename: Andrés H
authors.initials: AH
authors.lastname: Thomas
keywords: 2′-deoxyguanosine 5′-monophosphate; electron transfer; guanine radicals; photosensitization; pterin