Manipulation of protein fingerprints during on-column fluorescent labeling: protein fingerprinting of six Staphylococcus species by capillary electrophoresis

Bacterial proteomes were analyzed by use of electrophoretically mediated microanalysis (EMMA) and field-enhanced stacking. A water-soluble protein fraction was injected onto a capillary. Next, a fluorogenic reagent was injected and allowed to react with the protein mixture, producing fluorescent products that were separated by submicellar capillary electrophoresis and detected by laser-induced fluorescence. By use of a low-ionic strength sample buffer and a brief electrophoretic step, slow moving anionic proteins were stacked at the reagent-sample interface and were preferentially labeled. By reversing the order of sample injection and labeling reagent, fast moving cationic proteins were preferentially labeled. By adjustment of the sample buffer pH, proteins with different isoelectric points were selectively labeled. Electrophoresis fingerprints were generated for the water-soluble protein fraction from six Staphylococcus species. The protein patterns produced were species-specific and were used to construct a phylogenetic tree.