WebDiscard the supernatant. Wash cells twice in cold PBS. Collect cells by centrifugation at 2500 × g for 5 minutes. Add RIPA Bufer to the cell pellet. Use 1 mL of RIPA bufer for 40 mg (∼5 × 106 of HeLa cells) of wet cell pellet. Pipete the mixture up and down to suspend the pellet. Note: To increase yields, sonicate the pellet for 30 seconds ...