Free flow electrophoresis for the purification of proteins: I. Zone electrophoresis and isotachophoresis

The principles and some applications of free flow zone electrophoresis and isotachophoresis are described. The influence of (i) carrier electrolyte conductivity on the migration velocity and (ii) band shape on zone electrophoresis was investigated. The technique was found convenient for studying the effect of pH on the mobility of proteins to create a mobility curve. The purification of alcohol dehydrogenase from a crude yeast extract revealed the separation power of zone electrophoresis for complex protein mixtures. Without additional steps, a purification factor of 5.4, with a recovery of 97% alcohol dehydrogenase, was achieved. Free flow isotachophoresis was applied to the purification of immunoglobulins from human serum. Disadvantages of this technique are the time-consuming development of an optimized separation system and the empirical search for suitable spacers. Also, reaching of the steady state becomes increasingly difficult as the number of sample components increases.