Antigen purification by SDS-PAGE




Antigen for immunisation of rabbits or guinea pigs may be purified by preparative SDS-PAGE. Following electrophoresis and staining by aqueous Coomassie the band with the antigen is excised from the gel, cut into small gel pieces and homogenised in liquid nitrogen in a large mortar. The homogeneous powder is suspended in Freud'sches Adjuvans and injected into rabbits.


  1. Dissolve the antigen sample in Lämmli buffer. Boil for 5 min, Spin.
  2. Prepare a large PA gel: 1-2 mm spacer, 16x16 cm plates. Assemble the glass plates according to the Dobberstein procedure with silicon tubing as sealing.
  3. Prepare 50 ml for the separating gel and 10 ml for the stacking gel.
  4. Use a comb with only two slots: a small one for the MW marker, the remaining slots as a single slot for the sample (takes several ml)
  5. Run the gel at 60 mA for several hours with ventilation.
  6. carefully dissemble the glass plates
  7. stain in aqueous coomassie (0.5% Coomassie blue R-250 in water) overnight, recycle the staining solution
  8. wash several times with water. The destaining takes some time.
  9. Take a picture on the copy maschine.
  10. cut the band with the antigen with a blade. Compare to the molecular weight marker.
  11. cut the gel slice with a blade into small bits and pieces as much as possible.
  12. Transfer the gel material into a mortar filled with liquid nitrogen.
  13. Homogenise the small gel pieces with a pistle. Add liquid nitrogen from time to time.
  14. Homogenise until a fine powder is obtained. Bigger pieces must not be present.
  15. Transfer the powder into a 50 ml Falcon tube.
  16. Take a small aliquot of the powder, boil in Lämmli and analyse by SDS-PAGE to check whether you excised the correct protein.
  17. The frozen powder is ready for immunisation. The remaining SDS appears to be tolerated by the injected animal.