MB 660R Acid is a fluroescent agent with a terminal carboxylic acid group. MB 660R Acid very hydrophilic, water-soluble far-red fluorescent dye that has a maximal absorption of 665 nm and emission at 690 nm. The terminal carboxylic acid can react with primary amine groups in the presence of activators (e.g. EDC, or HATU) to form a stable amide bond. Reagent grade, for research purpose. Please contact us for GMP-grade inquiries.