Publication details
Oxidation potentials of guanine species
| Authors | |
|---|---|
| Year of publication | 2019 |
| Type | Article in Proceedings |
| Conference | XIX. Workshop of Biophysical Chemists and Electrochemists |
| MU Faculty or unit | |
| Citation | |
| Keywords | guanine; guanosine; deoxyguanosine; guanosine-5-monophosphate; 2-deoxyguanosine-5-monophosphate; thermodynamic redox potentials; density functional theory; B3LYP functional; 6-31+G set; linear sweep voltammetry; polymer pencil graphite electrode |
| Description | Guanine (G) belongs to the most easily oxidizable nucleobases which is well known from various experimental and theoretical studies. Our contribution is directed towards studies, in which we compare theoretical oxidation potentials with their experimentally measured values for guanine (G), guanosine (Guo), deoxyguanosine (dGuo), guanosine -5´- monophosphate (GMP) and 2´- deoxyguanosine -5´- monophosphate (dGMP). For determination of experimental oxidation potentials of all G species linear sweep voltammetry was applied using polymer pencil graphite electrodes (pPeGEs). It was found that the oxidation process for all studied derivatives is irreversible and strongly pH dependent. Anodic peak potentials increase in the order G << dGMP < GMP < dGuo < Guo and correlate well with the calculated thermodynamic redox potentials. For the determination of theoretical oxidation potentials the structures of G and its derivatives were optimized and the identities of minima were verified by vibration frequency calculations. Redox equilibria were modeled in terms of corresponding thermochemical cycles. The changes in free energy were calculated at DFT level using two different functionals: (a) general purpose B3LYP functional, and (b) a more specific omegaB97X-D functional, both based on a 6-31+G(d) set. Conformity of theoretical and experimental data for radicals (cationic or neutral, respectively) indicates that the deprotonation process of G differs from its analogues whereas the oxidation process of all species takes place on the imidazole ring. |