Effect of Zn2+ and Ca2+ Ions on Hydrogen Peroxide Photoproduction in Frozen Aqueous Solutions of Adenine Derivatives

Abstract

The content of hydrogen peroxide in aqueous 2 × 10–4 M solutions of adenine (A), adenosine (Ado), and adenosine-5'-diphosphate (ADP) containing NaCl (0.1 M) and identical solutions containing ZnCl2 and CaCl2 additions near UV-irradiated at 77 K was determined. The introduction of bivalent metal ions (2 × 10–4 M) differently affected the yield of H2O2 in different compounds. In A solutions, the addition of Zn2+ ions led to a yield of H2O2 increased more than 20-fold, and the addition of Ca2+ led to a 1.4-fold increase. In the case of Ado, the yield of H2O2 decreased 2.2- and 2.9-fold when Zn2+ and Ca2+ ions, respectively, were introduced in solutions. The addition of Zn2+ to ADP solutions led to a ~1.8-fold increase in the yield of H2O2. A comparison of the results of H2O2 determination in the systems with the estimated integral intensities of the EPR signals (IntS) of the irradiated solutions before defreezing (and estimated contents of the components of these spectra obtained by simulation) indicated that the main products of H2O2 formation in the systems were aggregates of adenine derivatives that formed during the freezing of aqueous solutions.