SIZE-DEPENDENT SEPARATION OF PROTEINS IN THE PRESENCE OF SODIUM DODECYL-SULFATE AND DEXTRAN IN CAPILLARY ELECTROPHORESIS - EFFECT OF MOLECULAR-WEIGHT OF DEXTRAN

Dextran solutions are widely used as sieving medium in protein analysi s by capillary electrophoresis in the presence of sodium dodecyl sulfa te. We studied the effect of dextran molecular weight on the separatio n efficiency using different dextran preparations with wide and very n arrow molecular weight distributions, in the range between 1270 and 20 00000. Migration times and band broadening of proteins were significan tly affected by the molecular weight of dextran. Migration times of pr oteins decreased as molecular weights of the dextrans decreased. Satis factory separation of all the proteins was possible with all dextrans except those with molecular weights of 70000 and 23800 where bovine se rum albumin and phosphorylase b failed to be separated. Unexpectedly r apid separation of all the proteins with enhanced resolution could be observed using two dextrans with a narrow molecular weight distributio n, with molecular weights of 1270 and 5220. Clearly the use of dextran with higher molecular weight is not the only way to achieve efficient separation of proteins. The separation mechanism in the presence of t he low molecular weight dextrans remains to be made clear in a future study.