Photosensitized oxidation of 2?-deoxyguanosine 5?-monophosphate: mechanism of the competitive reactions and product characterization

SERRANO, MARIANA P.; ESTÉBANEZ, SANDRA; VIGNONI, MARIANA; LORENTE, CAROLINA; VICENDO, PATRICIA; OLIVEROS, ESTHER; THOMAS, ANDRÉS H.

NEW JOURNAL OF CHEMISTRY

ROYAL SOC CHEMISTRY

Año: 2017 vol. 41 p. 7273 - 7282

1144-0546

UV-A radiation (320?400nm) induces modifications to differentbiomolecules through photosensitized reactions. Oxidized pterins are efficient photosensitizers that accumulate in theskin affected by vitiligo, and photoinduce the oxidation of guanine in aprocess initiated by an electron transfer from the nucleobase to the tripletexcited state of the photosensitizer. In this work, we have investigated thedegradation of 2?-deoxyguanosine 5?-monophosphate (dGMP) photosensitized bypterin (Ptr), the parent compound of oxidized pterins, in aqueous solutionsunder UV-A irradiation. We have identified five products containing theoxidized guanine moiety: the deoxyribonucleoside5?-monophophatederivatives of imidazolone, dehydroguanidinohydantoin,guanidinohydantoin, oxazolone and spiroiminodihydantoin. An additional productwith a much higher molecular weight, denoted P680, was also detected. The MS/MSanalyses show that this compound contains an intact guanine moiety and amodified one. The dependence of the rate of product formation on experimentalconditions was analyzed and a general mechanistic scheme is proposed.