This peptide is HiLyte Fluor 647 labeled Extendin-4 (Ex/Em=650 nm/675 nm). A cysteine residue has been added to the peptide N-terminus, and the dye is conjugated to this cysteine via the cysteine thiol moiety. Exendin-4, an agonist of glucagon-like peptide 1 (GLP-1) receptor, induces release of insulin after food intake. Exendin-4 shares a 53% sequence homology with GLP-1. Derived from Gila monster, Heloderma suspectum, Exendin-4 has a longer half life than GLP-1 in the plasma, thus making it a more potent insulinotropic agent.