Gram-preparative protein fractionation by isotachophoresis: isolation of human growth hormone isohormones.

Steady-state stacking (isotachophoresis) provides a preparative method in zone electrophoresis for the isolation of proteins in gram amounts. Up to four components were separated in 1000-fold larger quantities than those used in conventional electrophoresis. Separation occurs in order of free electrophoretic mobility. Recovery is nearly quantitative. The method was shown to be capable of resolving isohormones of human growth hormone. This fractionation is representative of difficult terminal isolations in biology. The best results are obtained when few components are fractionated at a high load. The method uses simple, small-scale apparatus. It does not utilize spacer ampholytes.