Synthesis, Conformal Analysis, and Antibody Binding of Staphylococcus aureus Capsular Polysaccharide Type 5 Oligosaccharides.

Staphylococcus aureus is one of the most prominent pathogens responsible for life-threatening hospital acquired infections. Most clinical isolates belong to serotype 5 or 8, which express unique capsular polysaccharides (CP), composed of the rare N-acetyl-β-d-mannosaminuronic acid (β-d-ManNAcA), N-acetyl-α-l-fucosamine (α-l-FucNAc) and N-acetyl-β-d-fucosamine (β-d-FucNAc) that can be used for the development of conjugate vaccines. Different acetylation patterns of CP5 create microheterogeneous polymers, carrying partial zwitterionic character, which may be important for immunological activity.

Mycobacterial Phenolic Glycolipid Triggers ATP-Mediated Neuronal P2X3 Signaling and Cough.

Cough drives respiratory pathogen transmission, yet how microbes directly engage host sensory neurons to trigger cough is largely unknown. We previously demonstrated that the (Mtb) glycolipid sulfolipid-1 (SL-1) activates neurons and induces cough. Here, we reveal that phenolic glycolipid (PGL) produced by the hypertransmissible HN878 Mtb strain activates both mouse and human nociceptive neurons in vitro using calcium imaging and electrophysiology and is sufficient to induce cough using plethysmography.

Influence of Halogen Atoms and the Reactivity of Nucleophiles on Reactions of Tetrahydropyran and Tetrahydrofuran Acetals with -Nucleophiles: Hyperconjugation and Inductive Effects.

Tetrahydropyran acetals bearing a fluorine atom adjacent to the acetal carbon atom can undergo highly stereoselective substitution reactions with nucleophilic alkenes to give the 1,2- products. By contrast, the chlorine- and bromine-substituted acetals give the 1,2- products. These results can be understood by considering oxocarbenium ion intermediates and their conformational preferences, which are dictated by hyperconjugative effects from axial substituents, with F ≪ H < Cl < Br.

Convergent Approach Toward ADP-Ribosylated Peptides via a Chemoselective Phosphate Condensation.

The preparation of well-defined ADP-ribosylated peptides is essential for studying the functional implications of this post-translational modification. While methodologies exist for the chemical synthesis of short oligo-ADPr fragments and mono-ADP-ribosylated peptides separately, combining the two distinct chemistries, required to assemble them, has remained challenging. In this research, we employ a methodology for the regio- and chemoselective condensation of two phosphomonoesters to convergently install the pyrophosphate bond in ADP-ribosylated constructs.

Photocatalytic Nitrene Radical Anion Generation from Sulfonyl Azides for Intermolecular Aziridination of Unactivated Alkenes.

Aziridines are important structures in the contemporary organic synthesis and are used for several biological applications. Herein, we show that aziridines can be readily synthesized from alkenes by the reductive activation of sulfonyl azides, mediated by photoredox catalysis. Mechanistic studies indicate that the reaction proceeds through reactive nitrene radical anions instead of the more commonly encountered triplet nitrenes.

Activity-Based Profiling of Retaining Glycosidases in Disease Diagnosis and Their Application in Drug Discovery.

Retaining glycosidases employ a two-step double displacement mechanism to hydrolyze their substrate glycosides. This mechanism involves a covalent enzyme-substrate adduct, and irreversible retaining glycosidase inhibitors have been designed based on this mechanism. Tagging such inhibitors with a reported moiety (biotin, fluorophore, bioorthogonal tag) provides activity-based retaining glycosidase probes.

Synthesis of a Set of Staphylococcus Aureus Capsular Polysaccharide Type 1 Oligosaccharides Carrying Taurine Esters.

Staphylococcus aureus is a Gram-positive bacterium that is responsible for severe nosocomial infections. The protective capsular polysaccharides (CPs), which are key elements of the cell wall, have been proposed as promising candidate antigens. Several CP types have been identified including CP1, CP5, and CP8, and serotype 1 has been associated with increased resistance to phagocytosis and virulence.

Bespoke Activity-Based Probes Reveal that the Endoglycosidase, PslG, Is an Endo-β-glucanase.

During infection, the human opportunistic pathogen Pseudomonas aeruginosa forms protective biofilms, whose matrix consists of proteins, nucleic acids, and polysaccharides such as alginate, Psl, and Pel. Psl, a polymeric pentasaccharide composed of mannose, rhamnose, and glucose, is produced during the early stages of biofilm formation, serving as a protective barrier against antibiotics and the immune system. The Psl biosynthesis gene cluster, besides encoding various glycosyltransferases, also includes an endoglycosidase, PslG.

Anti-phenolic glycolipid antibodies in infected cattle.

, the causative agent of bovine tuberculosis (bTB), causes significant financial losses in the agricultural industry. Additionally, transmission from animals to humans can result in zoonotic TB, especially in low- and middle-income countries (LMICs), highlighting the need to enhance One Health surveillance to mitigate this threat. Antibodies directed against a major mycobacterial cell wall component of , phenolic glycolipid-I (PGL-I), have shown excellent performance in identifying infection in humans and animals.

Neighboring-Group Participation by a Less Electron-Donating, Participating C-2-Ester Ensures Higher 1,2- Stereoselectivity in Nucleophilic Substitution Reactions of Furanosyl Acetals.

Nucleophilic substitution reactions of C-2-acyloxy furanosyl acetals can be highly diastereoselective. We here show that the presence of a less electron-donating -nitrobenzoyloxy group at C-2 of a furanosyl acetal can be of use to control the 1,2- stereoselectivity of acetal substitution reactions with higher stereoselectivity than the analogue with the more electron-donating benzoyloxy group, just as what was observed in the pyranosyl system. Computational results support a reaction manifold involving both open oxocarbenium ions and -dioxolenium ions to provide the 1,2- and 1,2- products.

Long, Synthetic Type 8 Capsular Oligosaccharides Reveal Structural Epitopes for Effective Immune Recognition.

is a Gram-positive bacterium that is responsible for severe nosocomial infections. The rise of multidrug-resistant strains, which can pose significant health threats, prompts the development of new treatment interventions, and much attention has been directed at the development of prophylactic and therapeutic vaccination strategies. Capsular polysaccharides (CPs) are key protective elements of the cell wall and have been proposed as promising candidate antigens.

Molecular properties of the RmlT wall teichoic acid rhamnosyltransferase that modulates virulence in Listeria monocytogenes.

Wall teichoic acids (WTAs) from the major Gram-positive foodborne pathogen Listeria monocytogenes are peptidoglycan-associated glycopolymers decorated by monosaccharides that, while not essential for bacterial growth, are required for bacterial virulence and resistance to antimicrobials. Here we report the structure and function of a bacterial WTAs rhamnosyltransferase, RmlT, strictly required for L. monocytogenes WTAs rhamnosylation.

Precision Activity-Based α-Amylase Probes for Dissection and Annotation of Linear and Branched-Chain Starch-Degrading Enzymes.

α-Amylases are the workhorse enzymes of starch degradation. They are central to human health, including as targets for anti-diabetic compounds, but are also the key enzymes in the industrial processing of starch for biofuels, corn syrups, brewing and detergents. Dissection of the activity, specificity and stability of α-amylases is crucial to understanding their biology and allowing their exploitation.

Mono-Palmitoyl-N-Alkylurea Ligands as Specific Activators of Human Toll-Like Receptor 2/6 Heterodimer.

Ligands for Toll-like-receptor 2 (TLR2) have demonstrated significant potential as immune-stimulating components in synthetic vaccines. Activation of TLR2 relies on the formation of dimeric complexes with either TLR1 or TLR6 and the nature of these dimers can impact therapeutic outcomes. The lipopeptide-based TLR2 ligands PamCysSK and PamCysSK have been extensively studied, and their recognition by different TLR-receptor heterodimers, TLR2/TLR1 and TLR2/TLR6, respectively, has been established.

Structure-guided design of C3-branched swainsonine as potent and selective human Golgi α-mannosidase (GMII) inhibitor.

The human Golgi α-mannosidase, hGMII, removes two mannose residues from GlcNAc-ManGlcNAc to produce GlcNAcManGlcNAc, the precursor of all complex -glycans including tumour-associated ones. The natural product GMII inhibitor, swainsonine, blocks processing of cancer-associated -glycans, but also inhibits the four other human α-mannosidases, rendering it unsuitable for clinical use. Our previous structure-guided screening of iminosugar pyrrolidine and piperidine fragments identified two micromolar hGMII inhibitors occupying the enzyme active pockets in adjacent, partially overlapping sites.

Synthesis and Biological Evaluation of Deoxycyclophellitols as Human Retaining β-Glucosidase Inhibitors.

Cyclophellitol is a potent and selective mechanism-based retaining β-glucosidase inhibitor that has served as a versatile starting point for the development of activity-based glycosidase probes (ABPs). We developed routes of synthesis of eight mono- and dideoxycyclophellitols and cyclophellitol aziridines, the latter as ABPs carrying either a biotin or fluorophore linked to the aziridine nitrogen. We reveal the potency of these 24 compounds as inhibitors of the three human retaining β-glucosidases, GBA1, GBA2 and GBA3.

Glycan-specific IgM is critical for human immunity to Staphylococcus aureus.

Staphylococcus aureus is a major human pathogen, yet the immune factors that protect against infection remain elusive. High titers of opsonic IgG antibodies, achieved in preclinical animal immunization studies, have consistently failed to provide protection in humans. Here, we investigate antibody responses to the conserved S.

From Mechanism-Based Retaining Glycosidase Inhibitors to Activity-Based Glycosidase Profiling.

Activity-based protein profiling (ABPP) is an effective technology for the identification and functional annotation of enzymes in complex biological samples. ABP designs are normally directed to an enzyme active site nucleophile, and within the field of Carbohydrate-Active Enzymes (CAZymes), ABPP has been most successful for those enzymes that feature such a residue: retaining glycosidases (GHs). Several mechanism-based covalent and irreversible retaining GH inhibitors have emerged over the past sixty years.

Mono-ADP-Ribosylation of Peptides: An Overview of Synthetic and Chemoenzymatic Methodologies.

Adenosine diphosphate (ADP)-ribosylation is a ubiquitous post-translational modification that regulates vital biological processes like histone reorganization and DNA-damage repair through the modification of various amino acid residues. Due to advances in mass-spectrometry, the collection of long-known ADP-ribose (ADPr) acceptor sites, e. g.

Transition transferases prime bacterial capsule polymerization.

Capsules are long-chain carbohydrate polymers that envelop the surfaces of many bacteria, protecting them from host immune responses. Capsule biosynthesis enzymes are potential drug targets and valuable biotechnological tools for generating vaccine antigens. Despite their importance, it remains unknown how structurally variable capsule polymers of Gram-negative pathogens are linked to the conserved glycolipid anchoring these virulence factors to the bacterial membrane.

Synthesis of Structural ADP-Ribose Analogues as Inhibitors for SARS-CoV-2 Macrodomain 1.

Protein adenosine diphosphate (ADP)-ribosylation is crucial for a proper immune response. Accordingly, viruses have evolved ADP-ribosyl hydrolases to remove these modifications, a prominent example being the SARS-CoV-2 NSP3 macrodomain, "Mac1". Consequently, inhibitors are developed by testing large libraries of small molecule candidates, with considerable success.

Semisynthetic Glycoconjugates as Potential Vaccine Candidates Against Haemophilus influenzae Type a.

Glycoconjugate vaccines are based on chemical conjugation of pathogen-associated carbohydrates with immunogenic carrier proteins and are considered a very cost-effective way to prevent infections. Most of the licensed glycoconjugate vaccines are composed of saccharide antigens extracted from bacterial sources. However, synthetic oligosaccharide antigens have become a promising alternative to natural polysaccharides with the advantage of being well-defined structures providing homogeneous conjugates.

Conformational and Electronic Variations in 1,2- and 1,5a-Cyclophellitols and their Impact on Retaining α-Glucosidase Inhibition.

Glycoside hydrolases (glycosidases) take part in myriad biological processes and are important therapeutic targets. Competitive and mechanism-based inhibitors are useful tools to dissect their biological role and comprise a good starting point for drug discovery. The natural product, cyclophellitol, a mechanism-based, covalent and irreversible retaining β-glucosidase inhibitor has inspired the design of diverse α- and β-glycosidase inhibitor and activity-based probe scaffolds.

Solid-Phase Synthesis and Biological Evaluation of Peptides ADP-Ribosylated at Histidine.

The transfer of an adenosine diphosphate (ADP) ribose moiety to a nucleophilic side chain by consumption of nicotinamide adenine dinucleotide is referred to as ADP-ribosylation, which allows for the spatiotemporal regulation of vital processes such as apoptosis and DNA repair. Recent mass-spectrometry based analyses of the "ADP-ribosylome" have identified histidine as ADP-ribose acceptor site. In order to study this modification, a fully synthetic strategy towards α-configured N(τ)- and N(π)-ADP-ribosylated histidine-containing peptides has been developed.