On the reproducibility of band position in electrophoretic separations

The reproducibility of protein migration was studied in three electrophoretic systems: sodium dodecyl‐sulfate electrophoresis on polyacrylamide gradient, isoelectric focusing on immobilized pH gradients and two‐dimensional charge‐size separations. The gradient gels were poured either with a two‐vessel apparatus or with a set of computer‐driven burettes, as described by Altland and Altland ( Electrophoresis 1984, 5 , 143–147). Standard deviation on band position was cut by 20–50% with the latter approach in comparison with the former. Typical results were: sodium dodecyl sulfate‐polyacrylamide gel electrophoresis, 0.6 mm (over a total length of 135 mm); immobilized pH gradients, 0.6 mm (for 179 mm length); two‐dimensional separations, 0.8 mm (χ‐axis), 0.6 mm ( y ‐axis).