Peptide mapping by capillary electrophoresis with Pluronic F127

Separation of peptides and proteins by capillary zone electrophoresis suffers from the interaction of these solutes with the capillary wall which results in the formation of broad peaks and low resolution. To minimize the protein/peptide-capillary wall interaction we tried to use Pluronic F127, a triblock copolymer of the general formula (polyethylene oxide)(x)(polypropylene oxide)(y)(polyethylene oxide)(z) when x=106, y=70 and z=106 which can be considered a surfactant capable of self-association both into isotropic and anisotropic gels. The analytes studied were enzymatic digests (obtained by trypsin or pepsin treatment) of insoluble matrix proteins from avian eggshell. The best separations were obtained by a system exploiting 10% Pluronic F127 in 20 mmol/l phosphate buffer, pH 2.5. Electrophoretic peptide profiles obtained were very complex owing to the complicated nature of the samples (the exact composition of the proteinous insoluble part of the eggshell is still unknown). The separation in phosphate buffer only offered complex maps of incompletely resolved peaks. The use of Pluronic F127 distinctly improved the separation with a considerably better resolution regarding both the number of peaks obtained and the quality of the separation.