Type I Photosensitization of 2'-deoxyadenosine 5'-monophosphate (5′-dAMP) by Biopterin and its Photoproduct Formylpterin

MARIANA P. SERRANO; CLAUDIO D. BORSARELLI; ANDRÉS H. THOMAS

PHOTOCHEMISTRY AND PHOTOBIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2013 vol. 89 p. 1456 - 1462

0031-8655

Biopterin (Bip) and its photoproducts 6-formylpterin (Fop) and 6-carboxypterin (Cap) accumulate in the skin of patients suffering from vitiligo, a chronic depigmentation disorder where the protection against UV radiation fails because of the lack of melanin. These compounds absorb in the UV-A inducing a potential photosensitizing action that can cause damage to DNA and other biomolecules. In this work, we have investigated the capability of these pterin derivatives(Pt) to act as photosensitizers under UV-A irradiation for the degradation of 2′-deoxyadenosine 5′-monophosphate (5′-dAMP) in aqueous solutions, as model DNA target. Steady-state and time-resolved experiments were performed and the effect of pH was evaluated. The results showed that photosensitized degradation of 5′-dAMP was only observed under acidic conditions, and a mechanistic analysis revealed the participation of the triplet excited state of the pterinderivatives (3Pt*) by electron transfer yielding the corresponding pair of radical ions (Pt?− and 5′-dAMP?+), with successive photosensitizer recovery by electron transfer from Pt?− to O2. Finally, 5′-dAMP?+ participates in subsequent reactions to yield degradation products.