By way of example, and not of limitation, proteins may be separated on the basis of isoelectric point (e.g. by chromatofocusing or isoelectric focusing), of electrophoretic mobility (e.g. by non-denaturing electrophoresis or by electrophoresis in the presence of a denaturing agent such as urea or sodium dodecyl sulfate (SDS), with or without prior exposure to a reducing agent such as 2-mercaptoeth