Linkage Analysis:
Unlike proteins and nucleic acids which are linear polymers with monomers linked in defined manner, the monosaccharides of a glycan polymer can link to one another in diverse ways.  Even a single hexose residue can have 4 hydroxyls capable of linking to other monomers of the chain (the hydroxyl at C1 is always linked in a polymer):

            Our lab uses the partially methylated alditol acetates analysis developed by Ciucanu and Kerek (link) to reveal just where these linkages are.  In this method, free hydroxyls are first methylated:

And the polymer is hydrolyzed then reduced with borodeuteride.  Lastly, the remaining hydroxyls, the ones which were involved in linkages are acetylated:

            Lastly the resulting molecules are subjected to GCMS with both the retention times and mass spectra compared to standards for identification: