CAPILLARY ELECTROPHORETIC RESOLUTION OF PHOSPHORYLATED PEPTIDE ISOMERS USING MICELLAR SOLUTIONS AND COATED CAPILLARIES

The addition of sodium dodecyl sulfate (SDS) micelles in the running b uffer can be used to resolve mono- and diphosphorylated isomers of the insulin receptor peptide by capillary electrophoresis. The effect of SDS on peptide resolution is very dependent on pH. Complete resolution of three monophosphorylated isomers is achieved in uncoated capillari es filled with phosphate buffer containing 25 mM SDS and buffered at p H 6.1. Resolution of the diphosphorylated isomers can be significantly improved by using polyacrylamide coated capillaries. In coated capill aries electroosmotic flow is negligible and the migration order of the isomers is reversed. This allows for a longer period of interaction b etween the diphosphorylated isomers and the micelle and therefore sele ctivity is improved. Efficiency of all peptide isomers was also improv ed in coated capillaries due to reduced adsorption to the capillary wa ll.