Labeling Antibodies Using N-Hydroxysuccinimide (NHS)-Fluorescein.

N-Hydroxysuccinimide (NHS)-ester derivatives are among the most commonly used reagents for labeling proteins. The method described here can be adapted to use practically any NHS fluorophore. Generally, a fluorophore is covalently bound to a macromolecule such as an antibody and acts as a reporter molecule used to measure the presence of the macromolecule. These fluorescently labeled bioactive reagents are suitable for use in immunofluorescence, flow cytometry, and numerous other biological applications. There are several widely used dyes available in convenient formats. This protocol can be used with any amine-reactive (e.g., PFP, isothiocyanate) fluorophore derivative.