Red fluorescent protein, also known as RFP or DsRed, is a 28-kDa fluorescent protein originating from the Discosoma coral. It has reported excitation and emission maxima at 558 and 583 nm, respectively. RFP is a commonly used fluorescent marker for protein localization, transgene expression, and monitoring other physiological processes in vivo. For additional immunochemical means of detection, commercial antibodies are available for RFP-tagged fusion proteins.