ATTO 635 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. The dye is very stable under physiological pH-values and in buffers up to pH 8.5. However, it slowly degrades at higher pH.

ATTO 635 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 - 650 nm. Suitable excitation sources for ATTO 635 are the 633 nm line of the He:Ne Laser or a Diode-Laser emitting at 635 nm.