Phycobiliproteins are a group of proteins with covalently attached linear tetrapyrrole chromophoric groups.These chromophoric groups are called bilins or phycobilins.The phycobiliproteins are water soluble, very stable at physiological pHs, and highly fluorescent proteins found in sea laver.They are usually divided into three separate groups based on their color and absorption properties, namely phycoerythrin (PE), phycocyanin (PC), and allo phycocyanin (APC).The absorption maxima are 565 nm for PE, 615 nm for PC, and 650 nm for APC, respectively.Purified phycobiliproteins have a variety of uses such as colorants in food and cosmetics.They are used most widely as fluorescent labels for cells and macromolecules in highly sensitive fluorescence techniques such as fluorescence-activated cell sorting, flow cytometry, fluorescence immunoassay, and fluorescence microscopy.