Polyacrylamide gradient electrophoresis for protein purification on the milligram scale.

A preparative-scale electrophoretic technique for protein fractionation and elution on a discontinuous gradient of acrylamide is described, which permits the separation and elution of a pure protein from a mixture containing 4-20 electrophoretically different proteins. The sharpness of the gradient electrophoretic resolution is demonstrated by the separation of proteins consisting of bovine serum albumin polymers and lactate dehydrogenase and enzymes such as acid phosphatase. The compositions of various discontinuous gradients of acrylamide and their application to enzyme purification are discussed. It was found that 60% of the enzyme activity loaded on the gel is recovered after gel fractionation and elution.