We suggest p-Nitrophenyl galacto-N-bioside (Galβ1-3GalNAcα1pNP, or Core1-pNP). Alternatively, fetuin (NEB #P6042S) can be digested with neuraminidase, and neuraminidase plus O-glycosidase. The changes in the molecular weight of fetuin after glycan removal can be observed by SDS-PAGE.