ATTO 550 NHS ester is manufactured by AAT Bioquest for research and development use. ATTO 550 is an orange fluorescent dye chemically related to the well-known Rhodamine 6G and Rhodamine B dyes. It is characterized by a strong absorption, a high fluorescence quantum yield, and excellent photostability and thermal stability. This dye exhibits moderate hydrophilicity, with an optimal excitation range of 540-565 nm. ATTO 550 is cationic and carries a net electrical charge of +1 after coupling to a substrate. This dye is well-suited for advanced applications in single-molecule detection and high-resolution microscopy techniques, including PALM, dSTORM, and STED microscopy. It is also compatible with flow cytometry (FACS), fluorescence in situ hybridization (FISH), and a variety of other biological assays. ATTO 550 can be used with excitation sources and fluorescence filters similar to those for Cy3® and TAMRA.

NHS esters react selectively and efficiently with primary amines (such as the side chains of lysine residues or aminosilane-coated surfaces) at pH 7-9, forming stable covalent amide bonds. This property makes ATTO 550 NHS ester an excellent choice for labeling peptides and amine-modified oligonucleotides. For labeling antibodies and other proteins, we highly recommend our iFluor® dyes that are highly water soluble and are optimized for labeling proteins.