Time-Resolved Lanthanide-based Resonance Energy Transfer (TR-LRET) detection of phosphorylation-dependent signals and fluorescence cross-interference. (A) Time-resolved luminescence emission spectra for SAStide-Cy5 (dashed line) and pSAStide-Cy5 (solid line). (B) 5-FAM-SFAStide-A (dashed line) and 5-FAM-pSFAStide-A (solid line). Spectra were collected from 15 µM peptide in the presence of 100 µM Tb3+ in 10 mM HEPES, 100 mM NaCl, pH 7.5, λex = 266 nm, in 50 µL total volume, 1 ms collection time, 50 µs delay time, and sensitivity 180. Data represent the average of experiments performed in triplicate.