text: The bioactive structures (native or 3D conformation or shape) of the isolated protein molecules do not undergo any significant conformational changes. Thus, active metal cofactor-containing proteins can be isolated reproducibly in the same fractions after a PAGE run. A shifting peak in the respective electropherogram indicates that the standardized time of gel polymerization (69 hr, RT) is not implemented in a PAGE experiment. A lower deviation of the standardized polymerization time (< 69 hr) stands for incomplete polymerization, and thus, for inherent instability due to gel softening during the cross-linking of polymers as the material reaches swelling equilibrium, whereas exceeding this time limit (> 69 hr) is an indicator of gel aging (cf. fig. Electropherogram). The phenomenon of gel aging is closely connected to long-term viscosity decrease of aqueous polyacrylamide solutions and increased swelling of hydrogels.
  Under standard conditions, metalloproteins with different molecular mass ranges and isoelectric points have been recovered in biologically active form at a quantitative yield of more than 95%. By preparative SDS-PAGE standard proteins (cytochrome c, aldolase, ovalbumin and bovine serum albumin) with molecular masses of 14–66 ku can be recovered with an average yield of about 73.6%. Preparative isotachophoresis (ITP) is applied for isolating palladium-containing proteins with molecular masses of 362 ku (recovery: 67%) and 158 ku (recovery: 97%).