Abstract: The disclosure relates to in vitro methods of detecting presence or absence of a target carbohydrate on a glycoprotein. The disclosure also relates to in vitro methods of detecting presence or absence of a glycan epitope on a glycoprotein.

Abstract: The disclosed methods involve deglycosylating a target molecule to remove target carbohydrates to create vacant glycosylation acceptor sites and then using glycosyltransferases to incorporate replacement carbohydrates into those sites. The methods also involve using glycosytransferases to incorporate new carbohydrates into vacant glycosylation acceptor sites without having to perform in vitro deglycosylation. The replacement or new carbohydrates include a click chemistry moiety that reacts to a click chemistry moiety on a label.