Patent ID: 7691603

Claim:
A method of forming a peptide conjugate comprising a covalent linkage between a modifying group and a glycosylated or non-glycosylated peptide, wherein said modifying group is conjugated to the peptide via a glycosyl linking group interposed between and covalently linked to both said peptide and said modifying group, said method comprising: a. contacting a cell with a modified sugar comprising a sialic acid moiety covalently functionalized with at least one modifying group, wherein said at least one modifying group is a water-soluble polymer; b. incubating said cell under conditions in which said cell internalizes said modified sugar; c. after step b, intracellularly contacting said modified sugar with a glycosylated or non-glycosylated peptide and a glycosyltransferase for which said modified sugar is a substrate, thereby forming said peptide conjugate.