Influence of Hg²⁺ on the Excited States of DNA: Photochemical Consequences

Abstract

Metal ions have been widely used as probes in excited-state studies of nucleic acids. One of the first demonstrations of triplet energy transfer in poly(A) and DNA was made by Bersohn and Eisenberg (1964), using Mn²⁺ as a triplet state quencher. These observations were extended by Eisinger and Shulman (1966) to include Co²⁺, Ni²⁺, and Cu²⁺ all of which were shown to quench long-range triplet transfer in poly(A) without quenching the fluorescence. Hélène and co-workers (see Hélène, 1973) showed that similar quenching mechanisms operated in adenosine aggregates but that, in addition, Cu⁺² quenched the adenosine fluorescence by singlet transfer to an adenosine-Cu²⁺ complex. Energy transfer methods, employing europium ions as energy traps have also been used to study fluorescence lifetimes and intersystem crossing yields of nucleic acid monomers at 25°C (Lamola and Eisinger, 1971).

Research supported by the Energy Research and Development Administration under contract with the Union Carbide Corporation.