Site-specific methods for preparation of glycoconjugates

Synthetic natural glycoproteins and neoglycoconjugates have multiple applications ranging from the study of glycobiology to potential therapeutics and detection of pathogens. However, the preparation of natural homogeneous glycoproteins or synthetic neoglycoconjugates is a challenging synthetic task. The aim of the research described in this thesis is to develop site-specific chemical and enzymatic methods for the preparation of well-defined glycoconjugates. Firstly, the use of sortase-mediated C-terminal ligation was investigated as a method for the preparation of a series of CTB-MUC1 glycoconjugates with the aim to identify antibody-like binding proteins with affinity for the ligated glycopeptide. Secondly, chemical ligation methods have been used to make multivalent neoglycoconjugate inhibitors of the bacterial enterotoxins, cholera toxin and verotoxin. Site-specific ligation of GM1 or Gb3 to a pentameric protein scaffold using a minimal length, bifunctional, and biorthogonal linker, resulted in inhibitors which display sub-nanomolar and micromolar IC50 values against CTB or VTB respectively, determined by ELLA inhibition studies.