Pseudomonas Aeruginosa is a Gram-negative bacterium which can form biofilms, increasing its resistance against antibiotics and the host immune system. Polysaccharides are an integral part of this... Show morePseudomonas Aeruginosa is a Gram-negative bacterium which can form biofilms, increasing its resistance against antibiotics and the host immune system. Polysaccharides are an integral part of this biofilm, one of these polysaccharides is called Psl. PslG is a glycosidase, able to cleave this polysaccharide, Psl, into smaller fragments. This decreases the antibiotic resistance of P. Aeruginosa. Interestingly PslG is produced by P. Aeruginosa itself, where it is found on the synthesis gene of Psl. The exact effects of PslG remain partly unknown. Moreover, only hypotheses have been made as to why P. Aeruginosa expresses such an enzyme. Here we have developed a set of activity-based probes based on Psl to discover the mode of action of PslG. Subsequently, a set of inhibitors have been designed based on the Psl motive and the mechanism of action of PslG. PslG was then co-crystallized with the inhibitors in order to study their binding interactions. Show less
In a typical glycosylation reaction, a donor is activated to form a (variety of) electrophilic species which can react with a nucleophilic acceptor, following a reaction mechanism having both SN1... Show moreIn a typical glycosylation reaction, a donor is activated to form a (variety of) electrophilic species which can react with a nucleophilic acceptor, following a reaction mechanism having both SN1 and SN2 character. On the SN1-side of the spectrum oxocarbenium ions partake in the mechanism while covalent intermediates act as the product forming intermediates on the SN2-side. The result of a glycosylation reaction is influenced by the properties of both donor and acceptor and can be affected by external factors as well. Because the challenges in carbohydrate synthesis are typically solved for a specific synthetic problem, a general understanding of what effect changing a single variable has on the mechanistic pathway, and thus the (stereochemical) outcome is not available. This in turn means that synthesis of glycosidic bonds typically requires a considerable amount of optimisation at the expense of a significant amount of time and resources. The goal of this thesis is to systematically investigate how changes in stereochemistry and protecting group patterns on the donor and acceptor affect the mechanism and outcome of glycosylation reactions, to enable a more rational design of synthesis routes. Show less