Anion-induced fluorescence quenching of a new zwitterionic biacridine derivative

The effect of halides and different buffer anions on the quenching of the f luorescence of the new probe 10,10'-bis(3-sulfopropyl)-9,9'-biacridine (SPB A) has been studied using fluorescence and decay time measurements. The lin earity of the Stern-Volmer plot indicates that fluorescence quenching by ha lides can be described reasonably well by a single-exponential decay with a K of 4.06 x 10(6) M-1 s(-1) for chloride, 7.83 x 106 M-1 s(-1) for bromide and 1.12 x 10(7) M-1 s(-1) for iodide, We have found that SPBA is collisio nally quenched also by the buffers 3-(N-morpholino)propanesulfonic acid (MO PS) and N-2-hydroxy-ethylpiperazine-N'-ethansulfonic acid (HEPES). The bimo lecular rate constants are 1.67 x 106 M-1 s(-1) for HEPES and 1.44 x 10(6) M-1 s(-1) for MOPS.