Date of Award

5-4-2020

Degree Type

Closed Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor

Jun Yin

Second Advisor

Binghe Wang

Third Advisor

Suri S. Iyer

Abstract

Glycans and glycoconjugates play pivotal roles in biology process, due to the diversity of glycans and the high complexity of glycan linkages, the obtains of glycan and glycoconjugates hinder the study of those structures. This work mainly focused on the synthesis of glycans, glycopeptides. Additionally, the application of those glycans and glycoconjugates were also demonstrated.

O-mannosyl glycans account for up to 30% of total O-linked glycans in the mammalian brain and play critical roles in cellular interaction-based pathologies. An efficient base synthesis/enzymatic extension (BSEE) strategy was developed to synthesize 45 O-mannosyl glycans. A disaccharide and two tetra-saccharide base structures linked with an N-a-Fmoc-threonine were firstly prepared via convergent chemistry in gram scale, followed by enzymatic extension utilizing a panel of robust bacterial glycosyltransferases and HPLC-based separation to afford a library of structurally well-defined O-mannosyl glycans. Glycan microarray analysis of lectins, anti-glycan antibodies and anti-sera against such glycans revealed fine specificities of these glycan binding proteins (GBPs), including branch preferences, side-chain influences.

O-GalNAc glycans play pivotal roles in diverse biological processes and aberrant O-GalNAc glycosylation is highly associated with tumor growth and progression. Efficient methods to assemble structurally defined O-glycans are limited. Herein, we report a facile chemoenzymatic strategy to systematically access diverse O-GalNAc glycans library. Additionally, the first O-GalNAc glycans array platform was established by using those glycans. The binding profiles of various glycan binding proteins was investigated by this platform. This strategy paves the way for collective synthesis of O-GalNAc glycans and the O-glycan array provides an efficient and convenient platform for the characterize of O-glycan binding proteins.

Glycosylations of IgG antibodies are known to influence their functions in physiological and pathological conditions. Changes in the glycosylation pattern of IgG antibodies affect their biological activity. Human serum IgG contain a single N-glycosylation site in the constant region of their heavy chain, which is occupied by biantennary, predominantly core-fucosylated and partially truncated oligosaccharides. Rapid identification and quantification of those glycosylation is currently unsolved. Herein, we reported a rapid quantification strategy of serum Ig glycosylation by using isotope labelled glycopeptides.

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