BioAuxilium Research 1 article published in JoVE Biochemistry Time-resolved Förster Resonance Energy Transfer Assays for Measurement of Endogenous Phosphorylated STAT Proteins in Human Cells Jaime Padros1, Geneviève Chatel1, Mireille Caron1 1BioAuxilium Research Time-resolved Förster resonance energy transfer cell-based assay protocols are described for the simple, specific, sensitive, and robust quantification of endogenous phosphorylated signal transducer and activator of transcription (STAT) 1/3/4/5/6 proteins in cell lysates in a 384-well format.