Immobilized Metal Affinity Polarization (IMAP) Assay: The MAPK13 blocking activity of test compounds was determined using an immobilized metal affinity polarization (IMAP) assay containing activated MAPK13, FITC-labeled substrate, and test compound. Full-length 6-His-tagged MAPK13 and constitutively active GST-MKK6 were prepared as described below. Activated MAPK13 was generated in 50 mM Hepes, 10 mM MgCl2 and 1 mM DTT, containing 1 uM MAPK13, 2 uM MKK6 and 50 uM ATP for 1 h at 25° C. MKK6 was removed by incubation with glutathione SEPHAROSE 4B beads (GE Healthcare Biosciences). MAPK13 activation was confirmed by Western blot using anti-phospho-p38-MAPK (T180/Y182) antibody (R& D Systems, Minneapolis, Minn.). IMAP assays were performed in 96-well non-treated half-area black plates or 384-well black plates (Corning Inc., Corning, N.Y.) in a final reaction volume of 20 ul using the linear phase of the rate kinetics. Assay reactions contained 0-100 uM test compound, 5-35 nM (EC80) activated MAPK13, 3 uM.