The Inhibitor Pack contains ready-to-use concentrated stock solutions of phosphatase and protease inhibitor cocktails. The phosphatase inhibitor solutions are for protection of phosphorylated residues of intercellular proteins against endogenous serine/threonine and tyrosine phosphatases during cell or tissue lysis. The protease inhibitor solution protects proteins against proteolytic degradation during lysate preparation. The solutions in the Inhibitor Pack are intended for use with Tris Lysis Buffer for preparation of lysates or with Diluent 39 for preparation of additional assay diluent.