Isoelectric focusing charge standards

Internal markers or standard proteins have most often been used by researchers to assure themselves that separations by electrophoresis are consistent and reproducible (21). In addition, charge markers In Isoelectric focusing are also used, although standard preparations of these materials are less reliable, especially under denaturing conditions. Other Internal standards that are often reported are materials for assuring radlolabel activity, enzyme activity, or other materials to monitor repeatability of measurements. In all cases, the stability of the standard material Is the key to long-term quality control. Large, batches of standards that are reproducible from lot to lot would also be useful. 

Different proteins have been carbamylated to be used as charge standards. Carbamylated beta chains of hemoglobin (38) were reported to be stable standards, while Fawcett (39) took the approach of acetylation of myoglobin to produce charge standards for isoelectric focusing. Building on these standards, Tollaksen et al. 

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