Updated project metadata. To test the hypothesis that HgCl2 acts as a phospho-tyrosine phosphatase inhibitor in B-cells, we treated the WEHI-231 cell line for 10 min with HgCl2 at 100 uM or 250 uM, okadaic acid at 100 nM or pervanadate at 25 uM and analyzed the phosphoproteome by TiO2 affinity chromatography and LC-MS/MS. WEHI-231 cell extracts were trypsinized and phosphopeptides were isolated using TiO2 affinity chromatography. Eluates were dried and resuspended in reversed-phase HPLC loading buffer for nano-flow HPLC, electrospray ionization and analysis on a Thermo LTQ mass spectrometer. Data were analyzed using the peptide prophet algorithm in Scaffold using Mascot and X!Tandem search results as input.