Whole cell lysates of A549 cells were prepared by hypotonic lysis in 50 mM NaCl, 10 mM Tris, pH 7.8, 2 mM EDTA, 1 % IGEPALCA-630, with protease inhibitor cocktail. Equal volumes of whole cell lysates were immunoprecipitated overnight with 4 Îźg of indicated antibody. Immunoprecipitates were captured on protein A magnetic beads and washed 4Ă in PBS. Samples were subjected to on-bead digestion and assayed for RelA using SID-SRM-MS [24]. Shown is mean +/- SD of RelA 756 signal relative to internal stable isotope standard (SIS). Note significant enrichment of RelA signal with each antibody. (PSD 150 kb
