Highly sensitive periodic acid/Schiff detection of bovine milk glycoproteins electrotransferred after nondenaturing electrophoresis, urea electrophoresis, and isoelectric focusing

Due to its lack of sensitivity, periodic acid/Schiff (PAS) staining of gels is not considered to be relevant for the detection of glycoproteins other than mucin-type glycoproteins after nondenaturing or urea polyacrylamide gel electrophoresis (PAGE). A simple and highly sensitive method was developed for the detection of bovine milk glycoproteins separated by nondenaturing PAGE, urea-PAGE, and isoelectric focusing. After electrophoresis, proteins were electrotransferred onto a polyvinylidene difluoride (PVDF) membrane and then glycoproteins were specifically stained by the Schiff's reagent after periodic acid oxidation. This method allowed the detection of the glycosylated forms of bovine -lactalbumin with sufficient sensitivity after nondenaturing PAGE or isoelectric focusing of whey proteins. Combination of isoelectric focusing and PAS detection on a PVDF membrane provided a resolutive tool in the characterization of the different glycoforms of casein and also of component PP3 of proteose peptones. Distinction between the non-glycosylated and glycoforms of -casein separated by urea-PAGE or isoelectric focusing was performed by comparing Coomassie blue staining and PAS staining. Moreover, amino-terminal microsequencing of glycoproteins immobilized on the membrane could be performed after PAS staining. bovine milk protein / glycoprotein / electrophoresis / isoelectric focusing / electroblotting / Schiff's reagent Rsum -Rvlation trs sensible des glycoprotines du lait bovin par le ractif de Schiff aprs lectrotransfert des protines spares par lectrophorse non dnaturante, lectrophorse en prsence d'ure et isolectrofocalisation. cause de sa faible sensibilit, la rvlation acide priodique / Schiff (PAS) n'est pas applicable pour la dtection des glycoprotines autres que les 775