ATTO 633 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, high thermal and photostability, and only little triplet formation. In common with most dye labels, absorption and fluorescence are independent of pH, at least in the range of pH 4 to 11, used in typical applications.

ATTO 633 and its derivatives are supplied as solvent-free perchlorate salts. 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 610 - 645 nm. Suitable excitation sources for ATTO 633 is the 633 nm line of the He:Ne Laser or a Diode-Laser emitting at 635 nm.