Synthesis of a cyclic tetramer of 3-amino-3-deoxyallose with axially oriented amino groups.

A linear tetramer of β-(1 → 6)-linked 3-azido-3-deoxy-d-allose containing glycosyl donor and glycosyl acceptor functions in the terminal monosaccharide units was prepared starting from 3-azido-3-deoxy-1,2:5,6-di-O-isopropylidene-α-d-allofuranose. Cyclization of the linear tetramer under glycosylation conditions afforded the corresponding cyclic tetrasaccharide in 77% yield; its deprotection and reduction of the azido groups resulted in the formation of the cyclic tetramer of 3-amino-3-deoxy-d-allose with axial amino groups, a potential scaffold for the synthesis of tetravalent functional clusters.

Broadly protective semi-synthetic glycoconjugate vaccine against pathogens capable of producing poly-β-(1→6)-N-acetyl-d-glucosamine exopolysaccharide.

Poly-β-(1→6)-N-acetylglucosamine (PNAG) was first discovered as a major component of biofilms formed by Staphylococcus aureus and some other staphylococci but later this exopolysaccharide was also found to be produced by pathogens of various nature. This common antigen is considered as a promising target for construction of a broadly protective vaccine. Extensive studies of PNAG, its de-N-acetylated derivative (dPNAG, containing around 15% of residual N-acetates) and their conjugates with Tetanus Toxoid (TT) revealed the crucial role of de-N-acetylated glucosamine units for the induction of protective immunity.

Tandem Electrospray Mass Spectrometry of Cyclic -Substituted Oligo-β-(1→6)-D-glucosamines.

High-resolution electrospray mass spectra (MS and MS/MS CID) of positive ions of a series of protonated, ammoniated, and metallated molecules of cyclic -substituted oligo-β-(1→6)-D-glucosamines differing in cycle size and -acyl substituents were registered and interpreted. It was shown that the main type of fragmentation is a cleavage of glycosidic bonds of a cycle, and in some cases fragmentation of amide side chains is possible. If labile fragments in substituents (e.

Neoglycoconjugate of Tetrasaccharide Representing One Repeating Unit of the Type 14 Capsular Polysaccharide Induces the Production of Opsonizing IgG1 Antibodies and Possesses the Highest Protective Activity As Compared to Hexa- and Octasaccharide Conjugates.

Identifying protective synthetic oligosaccharide (OS) epitopes of capsular polysaccharides (CPs) is an indispensable step in the development of third-generation carbohydrate pneumococcal vaccines. Synthetic tetra-, hexa-, and octasaccharide structurally related to CP of type 14 were coupled to bovine serum albumin (BSA), adjuvanted with aluminum hydroxide, and tested for their immunogenicity in mice upon intraperitoneal prime-boost immunizations. Injections of the conjugates induced production of opsonizing anti-OS IgG1 antibodies (Abs).

Trimodal Control of Ion-Transport Activity on Cyclo-oligo-(1→6)-β-D-glucosamine-Based Artificial Ion-Transport Systems.

Cyclo-oligo-(1→6)-β-D-glucosamines functionalized with hydrophobic tails are reported as a new class of transmembrane ion-transport system. These macrocycles with hydrophilic cavities were introduced as an alternative to cyclodextrins, which are supramolecular systems with hydrophobic cavities. The transport activities of these glycoconjugates were manipulated by altering the oligomericity of the macrocycles, as well as the length and number of attached tails.

High-resolution electrospray mass spectra of hexaethylene glycol connected biotinylated HNK-1 antigenic trisaccharide molecular probe and its non-sulfated analogue.

High-resolution electrospray mass spectra in positive and negative ion modes (MS and MS/MS) were measured and described for biotinylated hexaethylene glycol (HEG) connected molecular probes bearing HNK-1 (abbreviation of human natural killer cell-1 epitope) antigenic trisaccharide (1) and its non-sulfated analogue (2). For molecular probe 2, in its CID MS/MS of [M+2Na](2+), unexpected peak at m/z 530.2475 [C22H41N3O8SNa](+) was observed and attributed to the fragmentation of the aglycone at the end of the HEG chain distant from the biotin fragment.

Cyclo-oligo-(1 → 6)-β-D-glucosamine based artificial channels for tunable transmembrane ion transport.

Unimolecular ion channels were designed by functionalization of a new type of cyclic oligosaccharides, cyclo-oligo-(1 → 6)-β-d-glucosamines, with pentabutylene glycol chains. Their ion transporting activity was tuned by varying oligomericity. A halide selectivity sequence, Cl(-) > Br(-) > I(-) was observed.

A Poly-N-acetylglucosamine-Shiga toxin broad-spectrum conjugate vaccine for Shiga toxin-producing Escherichia coli.

Many pathogens produce the β-(1-6)-linked poly-N-acetylglucosamine (PNAG) surface polysaccharide that is being developed as a broadly protective antimicrobial vaccine. However, it is unknown whether systemically injected PNAG vaccines or antibodies would provide protective immunity against pathogens confined to the gastrointestinal tract such as Shiga toxin (Stx)-producing Escherichia coli (STEC), an important group of gastrointestinal (GI) pathogens for which effective immunotherapeutics are lacking. To ascertain whether systemic IgG antibody to PNAG impacts this infectious situation, a vaccine consisting of a synthetic nonamer of nonacetylated PNAG, 9GlcNH2, conjugated to the Shiga toxin 1b subunit (9GlcNH2-Stx1b) was produced.

Synthesis of multivalent carbohydrate-centered glycoclusters as nanomolar ligands of the bacterial lectin LecA from Pseudomonas aeruginosa.

A family of fifteen glycoclusters based on a cyclic oligo-(1→6)-β-D-glucosamine core has been designed as potential inhibitors of the bacterial lectin LecA with various valencies (from 2 to 4) and linkers. Evaluation of their binding properties towards LecA has been performed by a combination of hemagglutination inhibition assays (HIA), enzyme-linked lectin assays (ELLA), and isothermal titration microcalorimetry (ITC). Divalent ligands displayed dissociation constants in the sub-micromolar range and tetravalent ligands displayed low nanomolar affinities for this lectin.

Antibody to a conserved antigenic target is protective against diverse prokaryotic and eukaryotic pathogens.

Microbial capsular antigens are effective vaccines but are chemically and immunologically diverse, resulting in a major barrier to their use against multiple pathogens. A β-(1→6)-linked poly-N-acetyl-d-glucosamine (PNAG) surface capsule is synthesized by four proteins encoded in genetic loci designated intercellular adhesion in Staphylococcus aureus or polyglucosamine in selected Gram-negative bacterial pathogens. We report that many microbial pathogens lacking an identifiable intercellular adhesion or polyglucosamine locus produce PNAG, including Gram-positive, Gram-negative, and fungal pathogens, as well as protozoa, e.

Stereochemistry of intramolecular cyclization of tetra-β-(1→6)-D-glucosamines and related tetrasaccharides: the role of the conformational stereocontrol and the neighboring group participation.

The effect of reaction conditions, the nature of a leaving group, and a substituent at C-2 in the glycosylating monosaccharide on the stereochemical outcome of cyclization of linear tetra-β-(1→6)-d-glucosamines and some 'mixed' tetrasaccharides comprising glucose and glucosamine residues has been examined. Toluene and nitrile solvents improved the β-stereoselectivity of cyclization, however, the overall efficiency of the formation of cyclic products in these solvents was lower than that in dichloromethane. The use of bromide or pentenyl glycoside as leaving groups instead of the thioglycoside did not increase the β-stereoselectivity.

NMR and conformational studies of linear and cyclic oligo-(1→6)-β-D-glucosamines.

The conformational behavior of a series of linear and cyclic oligo-(1→6)-β-D-glucosamines and their N-acetylated derivatives, which are related to fragments of natural poly-N-acetylglucosamine, was studied by theoretical molecular modeling and experimental determination of transglycosidic vicinal coupling constants (3)J(C,H) and (3)J(H,H). Molecular dynamics simulations were performed under several types of conditions varying in the consideration of ionization of amino groups, solvent effect, and temperature. Neural network clustering and asphericity calculations were performed on the basis of molecular dynamics data.

Synthesis of five nona-β-(1→6)-d-glucosamines with various patterns of N-acetylation corresponding to the fragments of exopolysaccharide of Staphylococcus aureus.

A series of five 3-acetamidopropyl β-glycosides of nona-β-(1→6)-glucosamines containing two N-acetylglucosamine residues separated by a different number of glucosamine units with free amino groups have been synthesized using a convergent blockwise approach. Oxazoline glycosylation was used to introduce N-acetylglucosamine residues. These nonasaccharides are structurally related to the poly-N-acetylglucosamine (PNAG) extracellular polysaccharide of Staphylococcus aureus and can be used as models for biochemical and immunological studies.

Synthetic {beta}-(1->6)-linked N-acetylated and nonacetylated oligoglucosamines used to produce conjugate vaccines for bacterial pathogens.

Vaccines for pathogens usually target strain-specific surface antigens or toxins, and rarely is there broad antigenic specificity extending across multiple species. Protective antibodies for bacteria are usually specific for surface or capsular antigens. beta-(1-->6)-Poly-N-acetyl-d-glucosamine (PNAG) is a surface polysaccharide produced by many pathogens, including Staphylococcus aureus, Escherichia coli, Yersinia pestis, Bordetella pertussis, Acinetobacter baumannii, and others.

Synthesis of beta-(1-->6)-linked glucosamine oligosaccharides corresponding to fragments of the bacterial surface polysaccharide poly-N-acetylglucosamine.

A series of 3-beta-acetamidopropyl oligo-beta-(1-->6)-glucosamines consisting of 5, 7, 9 and 11 glucosamine residues, and a series of corresponding per-N-acetylated derivatives were synthesized using a convergent blockwise approach. These compounds represent fragments of a bacterial surface polysaccharide produced by numerous bacterial pathogens, including Staphylococcus aureus, and will be used as models for its biochemical and immunological properties.