Osmotic Shock

Reagents and Materials

  • Induced cultures of protein-producing bacteria
  • 20% w/v sucrose, 0.03 M Tris-HCl pH 8.0
  • Ice-cold 5mM MgSO4


  1. Culture and induce protein-producing bacteria
  2. Spin down the cells for 10 min at 4,000 rpm
  3. Re-suspend pellet in 10 ml of 20% w/v sucrose, 0.03 M Tris-HCl pH 8.0. Incubate for 10 minutes at room temperature
  4. Pellet cells at 4C for 10 minutes at 4,000 rpm
  5. Re-suspend pellet in 200µL of ice-cold 5mM MgSO4 and transfer into an eppendorf tube and let sit on ice bath for 30 minutes
  6. Spin at >13,000 rpm for 10 minutes. Carefully remove the supernatant and transfer to new tube
  7. Do SDS PAGE Gel analysis and store as required