1. Wash cells three times in cold PBS. 2. Resuspend cells in Cell Lysis Buffer 5 (diluted 1:5)* to a concentration of 1 x 107 cells/mL. 3. Freeze cells at ≤ -20 °C. Thaw cells with gentle mixing. Repeat the freeze/thaw cycle once. Trypan Blue and a microscope can be used to confirm cell lysis. Lysed cells will be blue. If cells are not lysed, repeat the freeze/thaw cycle as needed. 4. Centrifuge at 600 x g for 10 minutes at 2-8 °C to remove cellular debris. 5. Assay the supernate immediately or aliquot and store at ≤ -20 °C.