Polyacrylamide gel electrophoresis: recovery of non-stained and stained proteins from gel slices

Following electrophoresis or isoelectric focusing in gels of polyacrylamide the protein band of interest is cut out and placed above a sucrose gradient column, containing carrier ampholytes (Pharmalyte). By electrophoresis, isoelectric focusing or displacement electrophoresis the proteins migrate out of the gel slice and into the isoelectric focusing column for concentration and further purification. From this column, the proteins can be withdrawn and their isoelectric points determined. Even after staining with Coomassie Brilliant Blue at least some proteins can be recovered by this technique and used for further analyses, for instance amino acid determinations. The focusing in a pH gradient by carrier ampholytes can be replaced by an electrophoresis in a conductivity gradient column. However, in comparison with isoelectric focusing, this concentration technique has the drawback of not permitting further purification of the eluted protein.