Fluorescent Red Mega 485 NHS-ester is an amine conjugating fluorescent biolabel that can be used for covalent coupling to proteins and other biomolecules containing primary amino groups.Fluorescent red Mega 485 and other Mega dyes are specifically designed for multicolor techniques. It is characterized by an extremely large stoke′s shift between excitation and emission maxima. This dye is especially well suited for excitation by argon lasers or other short wavelength excitation light. This means that it can be excited with the same light source or filter arrangement than fluorescein and other widely used dyes as well as other Mega dye. Due to the different emission wavelength several different labels can be detected independently in the same experiment. Due to the small size of the Mega-labels and the direct conversion of excitation light into emission without using a FRET mechanism we foresee a variety of possible applications including DNA sequencing and FISH microscopy.