Phosphatase assay. (a) Schematic of unmasking assay. (b) PhospoFLAG peptide-coated microspheres incubated with YOP or without YOP. Phosphotyrosine (solid bars) and FLAG peptide (open bars) were detected with [Cy5]antiphosphotyrosine and [Cy5]anti-FLAG, respectively. (c) Time course of dephosphorylation. Various concentrations of YOP, 0 nM (♦), 1.5 nM (▾), 3 nM (▴), 6 nM (■), or 25 nM (●), were incubated with phosphoFLAG peptide-coated microspheres in the presence of [Cy5]anti-FLAG and scanned repeatedly at the indicated time intervals.