DNA as a mediator for proton, electron and energy transfer induced by metal ions

DNA interaction with H3O+, Mn2+, Cr3+, Co2+, Ni2+, Cu2+, Cu+, Zn2+, Ag+ and molecules of acridine orange and ethidium bromide dyes in ternary complexes DNA-intercalator-metal ion were studied with spectroscopic and thermodynamic methods. The principal goals are: study of DNA duplex role as a proton, electron and energy transfer. To achieve the goal we used new methodological approaches such as: (i) estimation of small frequency shift of chromophore molecule absorption band caused by change of surroundings by measuring the intensity of ultraviolet difference spectrum; (ii) development and testing new thermodynamic model of small ligands interaction with DNA that can establish direct proportional connection between the dynamic characteristics of the interaction, i.e. lifetime of the complex, and its equilibrium characteristics stability constants. Development of a new approach to photo reduction processes of metal ions in ternary complexes DNA-intercalator-metal ion, where the intercalator is a trap for light beam and DNA is an ordered surrounding that can strongly scatter both elastically and inelastically significal part of the falling light. It allows us to solve the following problems: (1) To explain fluorescence quenching of dyes intercalated in DNA by H3O+, Cu+ and Ag+ types of ions by electron transfer from intercalator to the ion connected with DNA; in the case DNA performs the role of mediator. (2) To solve the problem of estimation of high stability constants for DNA complexes with ions (log K > 8-10) by joint usage of kinetical methods for Cu+ oxidation in DNA complexes and UDS method for DNA complexes with Cu+ and Ag+. (3) To study UV spectroscopic display of proton double transfer in GC pairs of DNA induced both by local effect of H3O+ and transition metals, and macroscopic change of surroundings (high concentration of salt, ethanol, polyethyleneglycol, etc.). (4) Using highly sensitive nano quantity microelement DNA analysis to reveal risk factor at clinical investigations and DNA quality for its application to nano technology. (C) 2002 Elsevier Science B.V. All rights reserved.