SY-21 NHS ester

SY-21NHS Ester (QSY®-21 succinimidyl ester equivalent) is a nonfluorescent acceptor dye often used for preparation of peptide and oligonucleotide FRET probes. A broad and intense quenching range from 580 nm to 680 nm makes it useful as an acceptor in fluorescence resonance energy transfer (FRET) applications in conjunction with fluorescent dyes at 580 nm to 680 nm, such as Fluorescein, Alexa Fluor® 568, 594, 633, 647, TAMRA, ROX, Texas Red and Cy5.

The NHS ester (or succinimidyl ester) is the most popular amine reactive group for labeling with the primary amines of proteins (Lys), amine-modified oligonucleotides, and other amine-containing molecules. The labeling occurs most efficiently at pH 7-9 and forms a stable, covalent amide bond.