Protein concentration and recovery from gel slabs by displacement electrophoresis (isotachophoresis) and the effects of electroosmosis and counter flow

Alternative technical solutions of the concentration of protein samples or the recovery of proteins from gel slabs by displacement electrophoresis are demonstrated. The samples are collected at a boundary between high‐mobility leading ion and a low‐mobility terminating ion either in a small Sephadex G‐25 columns or in free solution in a rotating‐tube free electrophoresis apparatus. The boundary is kept stationary during electrophoresis by a counter flow of leading solution. Spacers and colored markers can be used to facilitate the collection of the proteins. Investigations showed that electroomosis is a very local phenomenon and that, as expected, the magnitude of the effects depends on the conductivity (field strength) of the solution. This implies that electroomosis will vary among different zones in a discontinuous system (as in displacement electrophoresis). Therefore, in most experiments om free solution it is very advantageous to arrange the system such that electrophoresis does not occur.