Chromofluorescent Indicator for Intracellular Zn<sup>2+</sup>/Hg<sup>2+</sup> Dynamic Exchange

The fluorescence of NABQ increases remarkably in the presence of Zn<sup>2+</sup> and is quenched by Hg<sup>2+</sup>. As shown by confocal imaging, NABQ−Zn<sup>2+</sup> can penetrate cells, where the bound Zn<sup>2+</sup> is exchanged for Hg<sup>2+</sup>. This results in the concomitant export of Hg<sup>2+</sup> from the cells, showing that NABQ can act as a Zn<sup>2+</sup> carrier and as a Hg<sup>2+</sup> extracting agent in living cells.