A Ratiometric Fluorescent Probe Based on FRET for Imaging Hg 2+ Ions in Living Cells

Mercury rising: A FRET-based ratiometric probe (see picture; FRET=fluorescence resonance energy transfer) can selectively detect Hg2+ ions on the parts-per-billion scale under physiological conditions. The probe undergoes a clear Hg2+-induced change in the intensity ratio of the two well-separated and equally intense emission bands of dipyrrometheneboron difluoride and rhodamine. Experiments show that the probe can be used in living cells.