Improved isolation and characterization procedure of sialylglycopeptide from egg yolk powder.

Sialylglycopeptide (SGP) is a complex bi-antennary N-glycan bearing a short peptide fragment that can be isolated from the yolk of hen eggs. This natural product has gained popularity as a starting material for the semi-synthesis of N-glycans. We have found that current isolation methods provide a glycopeptide contaminated with several related structures, one being a glycopeptide having a hexose directly attached to peptide backbone, most like through the hydroxyl containing side chain of the threonine moiety. Furthermore, current methods employ fresh egg yolks that need to be lyophilized and involve several tedious purification steps. Herein, we report a convenient method for the isolation of gram quantities of homogeneous SGP from commercially available egg yolk powder using solid/liquid extraction and HILIC-HPLC purification.