Flattening and/or expanding of pH gradients in isoelectric focusing gels exemplified with PhastSystem.

A simple method of flattening and/or expanding of pH gradients in isoelectric focusing is described for any pH interval desired: to modify pH gradients near one electrode a paper strip soaked with carrier ampholytes is applied onto the gel close to the opposite electrode. In order to flatten central parts of pH intervals paper strips are applied onto the gel at both electrodes. Conditions and criteria (e.g. amount and pH intervals of carrier ampholytes, width and localization of the paper strip, separation period) for optimization are presented with PhastSystem using ready-made gels with three different pH intervals and pI marker proteins (Pharmacia). Examples utilizing erythrocyte lysates are presented.