ATTO 643

ATTO 643 is a new fluorescent label related to the well known ATTO 647N. Characteristic features of the label are strong absorption and high thermal and photo-stability. The dye is very hydrophilic, hence it shows excellent water solubility and significantly reduced tendency for unspecific binding. ATTO 643 exhibits an extraordinary high fluorescence quantum yield. Contrary to many common fluorescent labels this is the case even when the dye is coupled to proteins, e.g. antibodies, streptavidin etc. The dye is highly suitable for single-molecule detection applications and high-resolution microscopy such as SIM, STED etc. The label is also highly recommended for oligonucleotide labeling, flow cytometry (FACS), fluorescence in-situ hybridization (FISH) and many more.
In common with most ATTO-labels, absorption and fluorescence are independent of pH, at least in the range of pH 2 to 11, used in typical applications. ATTO 643 is an anionic dye. After coupling to a substrate the dye carries a net electrical charge of -1. As supplied ATTO 643 consists of a mixture of three isomers with practically identical absorption and fluorescence properties. The fluorescence is excited most efficiently in the range 625 - 660 nm.