Photosensitized Damage on 2´-Desoxyguanosine-5´-Monophosphate in Solution Studied by ESI- and LDI- Mass Spectrometry

KARINA IVANA LEVY; MARIA MICAELA GONZALEZ; ROSA ERRA-BALSELLS; FRANCO M. CABRERIZO

Córdoba

Congreso; 16th International Congress on Photobiology; 2014

Oxidative damage on cellular DNA and its components can be induced by direct UV irradiation and by endogenous photosensitizers. Both processes are participant in aging process and many human diseases including cancer. The major target for DNA oxidants is guanine since it has the lowest oxidation potential of the DNA bases. The oxidation of guanine produces a wide spectrum of products including 8-oxo-7,8-dihydro-2´-guanine (8-oxoGua), spiroiminodihydantoin (Sp), guanidinohydantoin (Gh), 2,2,4-triamino-5(2H)-oxazolone (Ox). 8-OxoGua is considered a clinical biomarker for oxidative DNA damage. However, 8-oxoGua is more susceptible to further oxidation than guanine yielding more stable oxidation products, including Sp and Gh. B-Carbolines are natural alkaloids suggested as participant in a variety of photosensitized processes. Since humans are simultaneously exposed to b-carbolines and to sun light, the photosensitized mechanism needs to be elucidated. In this work, we have studied the capability of norharmane, a b-carboline, to induce 2´-desoxyguanosine-5´-monophosphate (dGMP) photooxidation upon UVA irradiation. Irradiated samples were analyzed by LDI- and ESI- mass spectrometry showing diagnostic signals related to Sp, Gh, 8-oxoGua and Ox moieties.