Calibrator 19 is a lyophilized blend of 3 recombinant proteins: Glucagon, Insulin, and Leptin. It is intended for use as an assay calibrator for MSD U-PLEX mouse or rat assays that measure any of the included analytes. The utility of this product has not been evaluated in other applications. Individual analyte concentrations are provided in the lot-specific certificates of analysis. Human Glucagon and Insulin, and rat Leptin were expressed in E. coli.