Photosensitized electron transfer within self-assembled norharmane/2´-deoxyadenosine-5´-monophosphate (dAMP) complex

M. MICAELA GONZALEZ; FEDERICO A. O. RASSE SURIANI; CARLOS A. FRANCA; REINALDO PIS DIEZ; YOUSEF GHOLIPOUR; H. NONAMI; ROSA ERRA-BALSELLS; FRANCO M. CABRERIZO

ORGANIC & BIOMOLECULAR CHEMISTRY

ROYAL SOC CHEMISTRY

Lugar: CAMBRIDGE; Año: 2012 p. 9359 - 9372

1477-0520

Norharmane is a compound that belongs to a family of alkaloids called beta-carbolines (bCs). These alkaloids are present in a wide range of biological systems, playing a variety of significant photodependent roles. Upon UV-A irradiation, bCs are able to act as efficient photosensitizers. In this work, we have investigated the photosensitized oxidation of 2-deoxyadenosine 5-monophosphate (dAMP) by norharmane in an aqueous phase, upon UV-A (350 nm) irradiation. The effect of the pH was evaluated on both the interactions between norharmane and dAMP in the ground and electronic excited states, and on the dAMP photosensitized oxidation. A quite strong static interaction between norharmane and dAMP was observed, especially under those pH conditions where the protonated form of the alkaloid is present (pH minor 7). Theoretical studies were performed to further characterize the static complex structure. The participation of reactive oxygen species (ROS) in the photosensitized reaction was also investigated and the photoproducts were characterized by means of UV-LDI-MS and ESI-MS. All the data provided herein indicate that electron transfer (Type I) within a self-assembled norharmane-dAMP complex is the operative mechanism in the dAMP photosensitization.