Labeling a protein with fluorophores using NHS ester derivitization.

N-hydroxysuccinimde (NHS) ester-mediated derivitization involves the reaction of this amine-reactive group with the primary amines of a protein or a biomolecule. Using NHS chemistry allows one to conjugate various fluorescent probes, biotin, and cross-linkers to primary amines. For example, we use NHS ester chemistry to fluorescently label the amino terminus of a protein with the dye, 5-(and-6)-carboxyfluorescein, succinimidyl ester (5(6)-FAM, SE).