Synthesis and Fluorescence Quenching Study of the Novel Cationic Probe Derived from Luminarosine

A simple and efficient transformation of the zwitterionic luminarosine into a brightly fluorescent cationic analogue, namely 1-amino-9-methoxy-2,4,10-triaza-4b-azoniaphenanthrene (3) is reported. The fluorescence quenching of 3 by common nucleotides calf-thymus (CT) DNA, and halide ions was investigated by means of spectrophotometric and spectrofluorometric methods. Intermolecular static and dynamic fluorescence-quenching constants for quenching of 3 by nucleotides and halide ions were determined in aqueous solution. Evidence for formation of nonfluorescent ground-state complexes of 3 with nucleotides and CT-DNA is presented. Scatchard analysis of the CT-DNA quenching data resulted in a binding constant of 2.8 x 10(4) M-1 and a number of binding sites per base pair of 0.049.