ATTO 611X belongs to a new generation of fluorescent labels for the red spectral region. Characteristic features of the label are strong absorption, high fluorescence quantum yield, exceptionally large Stokes-Shift of 70 nm, high photo-stability, and only little triplet formation. Above pH 5.0 the dye exists in an equilibrium with a colourless form (pH 7.0: 50% of the dye are converted). This is a reversible reaction, which does not interfere with the process of coupling to proteins etc. On lowering the pH absorption and fluorescence are restored fully.

ATTO 611X is a cationic dye supplied as a solvent-free tetrafluoroborate salt. The dye is moderately hydrophilic. Its NHS-ester and maleimide show excellent solubility in polar solvents like DMF, DMSO or acetonitrile. For details of coupling see our recommended labeling procedure (PDF). The fluorescence is excited most efficiently in the range 590 - 630 nm.