Fluorescence Quenching of 9-Aminoacridines by Purine Mononucleotides

Article abstract of DOI:10.1021/j100459a005

The kinetics of fluorescence quenching of 9-aminoacridine (9AA) and 9-amino-10-methylacridinium (10Me-9AA) by purine mononucleotides (adenosine 5'-monophosphate (AMP) and guanosine 5'-monophosphate (GMP)) has been studied over the temperature range of 25-46 deg C in 0.1 M phosphate buffer (pH 7.0).A set of quenching parameters has been obtained on the basis of the kinetic scheme which takes into account complex formation in the ground state as well as in the excited singlet state. Both steady-state and transient fluorescence measurements have been carried out in order to determine rate constants.The rate constant for the complex formation is found to be 3.5E9 - 7E9 M^-1 s^-1, indicating that the reaction is a diffusion-controlled one, while the rate constant for the complex dissociation is found to be much smaller than that for the complex formation.The dye-GMP complex is shown to relax nonradiatively, whereas the dye-AMP complerr is accompanied by weak fluorescence and its decay kinetics obeys a double-exponential decay law.It is found that the quenching behavior for the mutagenic dye 9AA is very similar to that for the nonmutagenic dye 10Me-9AA.Thermodynamic properties for the complex formation are also discussed.