Group A Carbohydrate (GAC), conjugated to an appropriate carrier protein, has been proposed as an attractive vaccine candidate against Group A Streptococcus infections. Native GAC consists of a... Show moreGroup A Carbohydrate (GAC), conjugated to an appropriate carrier protein, has been proposed as an attractive vaccine candidate against Group A Streptococcus infections. Native GAC consists of a polyrhamnose (polyRha) backbone with N-acetylglucosamine (GlcNAc) at every second rhamnose residue. Both native GAC and the polyRha backbone have been proposed as vaccine components. Here, chemical synthesis and glycoengineering were used to generate a panel of different length GAC and polyrhamnose fragments. Biochemical analyses were performed confirming that the epitope motif of GAC is composed of GlcNAc in the context of the polyrhamnose backbone. Conjugates from GAC isolated and purified from a bacterial strain and polyRha genetically expressed in E. coli and with similar molecular size to GAC were compared in different animal models. The GAC conjugate elicited higher anti-GAC IgG levels with stronger binding capacity to Group A Streptococcus strains than the polyRha one, both in mice and in rabbits. This work contributes to the development of a vaccine against Group A Streptococcus suggesting GAC as preferable saccharide antigen to include in the vaccine. Show less
Endolysin enzymes from bacteriophage cause bacterial lysis by degrading the peptidoglycan cell wall. The streptococcal C1 phage endolysin PlyC, is the most potent endolysin described to date and... Show moreEndolysin enzymes from bacteriophage cause bacterial lysis by degrading the peptidoglycan cell wall. The streptococcal C1 phage endolysin PlyC, is the most potent endolysin described to date and can rapidly lyse group A, C, and E streptococci. PlyC is known to bind the Group A streptococcal cell wall, but the specific molecular target or the binding site within PlyC remain uncharacterized. Here we report for the first time, that the polyrhamnose backbone of the Group A streptococcal cell wall is the binding target of PlyC. We have also characterized the putative rhamnose binding groove of PlyC and found four key residues that were critical to either the folding or the cell wall binding action of PlyC. Based on our results, we suggest that the interaction between PlyC and the cell wall may not be a high-affinity interaction as previously proposed, but rather a high avidity one, allowing for PlyC's remarkable lytic activity. Resistance to our current antibiotics is reaching crisis levels and there is an urgent need to develop the antibacterial agents with new modes of action. A detailed understanding of this potent endolysin may facilitate future developments of PlyC as a tool against the rise of antibiotic resistance. Show less
In this work a photosubstitution strategy is presented that can be used for the isolation of chiral organometallic complexes. A series of five cyclometalated complexes Ru(phbpy)(N−N)(DMSO-κS)](PF6)... Show moreIn this work a photosubstitution strategy is presented that can be used for the isolation of chiral organometallic complexes. A series of five cyclometalated complexes Ru(phbpy)(N−N)(DMSO-κS)](PF6) ([1]PF6-[5]PF6) were synthesized and characterized, where Hphbpy = 6′-phenyl-2,2′-bipyridyl, and N–N = bpy (2,2′-bipyridine), phen (1,10-phenanthroline), dpq (pyrazino[2,3-f][1,10]phenanthroline), dppz (dipyrido[3,2-a:2′,3′-c]phenazine, or dppn (benzo[i]dipyrido[3,2-a,2′,3′-c]phenazine), respectively. Due to the asymmetry of the cyclometalated phbpy– ligand, the corresponding [Ru(phbpy)(N–N)(DMSO-κS)]+complexes are chiral. The exceptional thermal inertness of the Ru–S bond made chiral resolution of these complexes by thermal ligand exchange impossible. However, photosubstitution by visible light irradiation in acetonitrile was possible for three of the five complexes ([1]PF6-[3]PF6). Further thermal coordination of the chiral sulfoxide (R)-methyl p-tolylsulfoxide to the photoproduct [Ru(phbpy)(phen)(NCMe)]PF6, followed by reverse phase HPLC, led to the separation and characterization of the two diastereoisomers of [Ru(phbpy)(phen)(MeSO(C7H7))]PF6, thus providing a new photochemical approach toward the synthesis of chiral cyclometalated ruthenium(II) complexes. Full photochemical, electrochemical, and frontier orbital characterization of the cyclometalated complexes [1]PF6-[5]PF6 was performed to explain why [4]PF6 and [5]PF6 are photochemically inert while [1]PF6-[3]PF6 perform selective photosubstitution. Show less
Volbeda, A.G.; Marel, G.A. van der; Codée, J.D.C. 2018
Carbohydrates are the most densely functionalized class of biopolymers in nature. This chapter describes the differences in the reactivity of the various functional groups on a carbohydrate ring... Show moreCarbohydrates are the most densely functionalized class of biopolymers in nature. This chapter describes the differences in the reactivity of the various functional groups on a carbohydrate ring and how to exploit these in the design of effective protecting group strategies. It then describes how protecting group effects can be used to control stereoselective transformations and reactivity‐controlled one‐pot synthesis strategies. The chapter highlights applications and strategies in automated synthesis. Different strategies have been developed to automate oligosaccharide assembly based on either solution‐phase synthesis or solid‐phase techniques, and automated solid‐phase synthesizers are now commercially available. Protecting group chemistry can make or break any (oligo)saccharide synthesis effort. The impact of protecting groups on the stereochemical outcome of a glycosylation reaction is best illustrated by the anchimeric assistance that neighboring groups can provide during a glycosylation reaction. Show less
The thesis focuses on synthesis strategies in oligosaccharide campaigns, and the influence of protecting groups. New protecting group deprotection methods and protecting groups are developed.... Show moreThe thesis focuses on synthesis strategies in oligosaccharide campaigns, and the influence of protecting groups. New protecting group deprotection methods and protecting groups are developed. These novelties are applied in the synthesis of oligosaccharides which represent interesting biological targets. A solid phase approach is used to construct a library of oligorhamnans, employing a protecting group developed in this thesis. A fast deprotection method is employed to selectively remove fucntionalized benzyl ethers, which allows for the introduction of functional groups on a mannuronic acid molecule. Future synthesis campaigns are drafted combining the methods used in the previous chapters. Show less
Volbeda, A.G.; Mechelen, J. van; Meeuwenoord, N.; Overkleeft, H.S.; Marel, G.A. van der; Codee, J.D.C. 2017
