red 21

Red 21 is a dye.

Pigment Red 21 is a multifunctional dye used in biological experiments to help researchers observe and analyze cell structures, track biomolecules, evaluate cell functions, distinguish cell types, detect biomolecules, study tissue pathology, and monitor microorganisms. Its applications span from basic scientific research to clinical diagnostics. Additionally, dyes are widely employed in traditional fields like textile dyeing, and in emerging fields such as functional textile processing, food pigments, and dye-sensitized solar cells.

QSY-21 is a fluorescence quencher with broad absorption in the far-red and near-infrared regions, effectively quenching the fluorescence of dyes that emit in these areas. It is a carboxylic acid derivative with a strong maximum absorption at 661 nm, making it a suitable acceptor for fluorescence resonance energy transfer (FRET) applications. QSY-21 is commonly used as a quencher for Cyanine5, Cyanine5.5, AF 647, or other spectrally similar fluorescent dyes.

QSY 21 NHS is an effective energy transfer acceptor for far-red and near-infrared fluorescent probes. This quencher operates within the wavelength range of 540-750 nm, typically utilized in FRET applications. QSY 21 NHS does not emit fluorescence under normal conditions. The NHS ester form of QSY 21 allows for the labeling of proteins, amine-modified oligonucleotides, and other primary amine-containing molecules (R-NH2).