ATTO 520 is a new fluorescent label related to the well-known dye Rhodamine 6G. Characteristic features of the label are strong absorption, high fluorescence quantum yield, high thermal and photostability, and only little triplet formation.

ATTO 520 is a cationic dye supplied as a crystalline solvent-free perchlorate 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 510 - 535 nm. The dye can be excited for instance with an Argon-Ion laser using the 514 nm line.