Oxidation and reduction potentials of 8-vinyladenosine measured by cyclic voltammetry: Implications for photoinduced electron transfer quenching of a fluorescent adenine analog

8-Vinyladenosine (8VA) is an adenine analog that effectively base pairs with thymine in duplex DNA. With a red-shifted absorption band centered around 290 nm excited 8VA emits Stokes-shifted fluorescence centered at 370 nm. The fluorescence quantum yield of 8VA* is sensitive to base stacking, making it an effective reporter of DNA structure and dynamics. We have performed cyclic voltammetry (CV) studies on 8VA in aprotic organic solvents to explore the mechanism of fluorescence quenching. Excited state oxidation and reduction potentials were calculated from the experimentally determined ground state one electron redox potentials. The Rehm–Weller equation was used to obtain the free energies of electron transfer for native nucleobase monophosphate oxidation and reduction paired with 8VA*. The magnitude and sign of the free energies have been used to assess whether electron transfer is thermodynamically plausible. The results suggest that electron transfer to or from 8VA* may not be the dominant mechanism of quenching for AMP, CMP, and perhaps GMP. In contrast, TMP may be an effective electron acceptor. Taken together, the results suggest that 8VA* quenching by nucleobase monophosphates in aqueous solution proceeds through a different mechanism than ET.

► Redox potentials of 8VA were measured in aprotic solvents by cyclic voltammetry.
► PCM/DFT calculations confirm the measured oxidation and reduction potentials.
► Excited state redox potentials for 8VA were obtained from the Rehm–Weller equation.
► The results suggest that electron transfer is not the major quenching pathway.