Studies of the binding of ethidium bromide to transfer ribonucleic acid: Absorption, fluorescence, ultracentrifugation and kinetic investigations

Abstract

Ethidium bromide forms a complex with Escherichia coli transfer ribonucleic acid that exhibits many similarities to the deoxyribonucleic acid-ethidium bromide complex. Evidence for the strong interaction is obtained from ultracentrifugation, absorption and fluorescence studies and thermal denaturation profiles. The existence of strong and weak binding sites is indicated by spectrophotometry and spectrofluorometry. The reversibility of complex formation is shown by thermal renaturation studies and by the kinetics of the dissociation, from which it is concluded that several forms of the complex are present at equilibrium. The kinetics of the association reaction reveal the presence of a fast binding process followed by several slow unimolecular steps.