ATTO 565 NHS ester

ATTO 565 NHS ester is a commonly used amine-reactive rhodamine dye. It might be used for labeling peptides, proteins and other amino-containing compounds such as amino-modified oligos. It readily reacts with compounds containing amino groups, forming a chemically stable amide bond between the dye and amino compounds. The optimum pH range for NHS-ester coupling is pH 8.0 – 9.0. At this pH, amino groups of proteins (such as the ε-amino groups of lysines) are unprotonated enough for fast coupling. ATTO 565 NHS ester has strong absorption, high fluorescence quantum yield and high thermal/photostability. However, it has low water solubility. For the applications that require high water solubility, you may consider iFluor® 568 succinimidyl ester that has almost identical fluorescence properties with greatly enhanced water solubility. In addition, the protein conjugates made from iFluor® 568 succinimidyl ester are much brighter than those from ATTO 565 NHS ester.