Interactions of several polycyclic aromatic hydrocarbons with DNA base molecules studied by absorption spectroscopy and fluorescence quenching

Abstract

The interactions of several polycyclic aromatic hydrocarbons (PAHs) including benzo[ a]pyrene, benzo[ e]pyrene, benz[ a]anthracene, 7,12-dimethylbenz[ a]anthracene, 3-methylcholanthrene, dibenz[ a, c]anthracene and dibenz[ a, h]anthracene with selected deoxyribonucleic acid (DNA) bases, i.e. adenine, thymine, cytosine and 5-methylcytosine, and a nucleoside, guanosine, have been studied employing UV-visible absorption spectroscopy, fluorescence quenching and electrochemical measurements. The results indicate that PAHs interact with DNA bases by forming modernately strong 1:1 charge transfer (CT) complexes in their ground state. The fluorescence of PAHs was only quenched by 5-methylcytosine, quanosine and cytosine, and this was at lower than diffusion controlled rates in dimethyl sulfoxide. The fluorescence quenching rate constants showed a better inverse correlation with the solvent reorganization energies than with the free energies of activation calculated using the Marcus model of electron transfer.