R-Phycoerythrin (R-PE), a fluorescent protein from phycobiliprotein family, is isolated from Acrochaetium sp. Its absorption peak is at 566 nm and a fluorescence emission peak at 575 nm. It is a large molecule used for fluorescence-based detection, primarily in flow cytometry, microarray assays, ELISAs, and other applications. It's the most intensely fluorescent phycobiliproteins having red fluorescence with high sensitivity and photostability.