Multivalent inhibition of the Aspergillus fumigatus KDNase.

Aspergillus fumigatus is a saprophytic fungus and opportunistic pathogen often causing fatal infections in immunocompromised patients. Recently AfKDNAse, an exoglycosidase hydrolyzing 3-deoxy-D-galacto-D-glycero-nonulosonic acid (KDN), a rare sugar from the sialic acid family, was identified and characterized. The principal function of AfKDNAse is still unclear, but a study suggests a critical role in fungal cell wall morphology and virulence. Potent AfKDNAse inhibitors are required to better probe the enzyme's biological role and as potential antivirulence factors. In this work, we developed a set of AfKDNAse inhibitors based on enzymatically stable thio-KDN motifs. C2, C9-linked heterodi-KDN were designed to fit into unusually close KDN sugar binding pockets in the protein. A polymeric compound with an average of 54 KDN motifs was also designed by click chemistry. Inhibitory assays performed on recombinant AfKDNAse showed a moderate and strong enzymatic inhibition for the two classes of compounds, respectively. The poly-KDN showed more than a nine hundred fold improved inhibitory activity (IC50 = 1.52 ± 0.37 µM, 17-fold in a KDN molar basis) compared to a monovalent KDN reference, and is to our knowledge, the best synthetic inhibitor described for a KDNase. Multivalency appears to be a relevant strategy for the design of potent KDNase inhibitors. Importantly, poly-KDN was shown to strongly decrease filamentation when co-cultured with A. fumigatus at micromolar concentrations, opening interesting perspectives in the development of antivirulence factors.

ROMP-based Glycopolymers with High Affinity for Mannose-Binding Lectins.

Well-defined, highly reactive poly(norbornenyl azlactone)s of controlled length (number-average degree of polymerization DPn¯ = 10 to 1,000) were made by ring-opening metathesis polymerization (ROMP) of pure exo-norbornenyl azlactone. These were converted into glycopolymers using a facile postpolymerization modification (PPM) strategy based on click aminolysis of azlactone side groups by amino-functionalized glycosides. Pegylated mannoside, heptyl-mannoside, and pegylated glucoside were used in the PPM. Binding inhibition of the resulting glycopolymers was evaluated against a lectin panel (Bc2L-A, FimH, langerin, DC-SIGN, ConA). Inhibition profiles depended on the sugars and the degrees of polymerization. Glycopolymers from pegylated-mannoside-functionalized polynorbornene, with DPn¯ = 100, showed strong binding inhibition, with subnanomolar range inhibitory concentrations (IC50s). Polymers surpassed the inhibitory potential of their monovalent analogues by four to five orders of magnitude thanks to a multivalent (synergistic) effect. Sugar-functionalized poly(norbornenyl azlactone)s are therefore promising tools to study multivalent carbohydrate-lectin interactions and for applications against lectin-promoted bacterial/viral binding to host cells.

Pseudomonas aeruginosa resistance of monosaccharide-functionalized glass surfaces.

Preventing microorganism colonization on a surface is a great challenge in the conception of medical, food and marine devices. Here, we describe the formation of carbohydrate functionalized glass surfaces with D-glucose, D-galactose and D-mannose and how they efficiently affected the bacterial attachment. The carbohydrate entities were covalently attached to the pre-functionalized surface by click chemistry thanks the copper catalysed alkyl-azide cycloaddition. Water contact angle and X-ray photoelectron spectroscopy characterisations showed a homogeneous and quantitative cycloaddition at the scale of microorganisms. The adhesion assays with Pseudomonas aeruginosa, used as model of opportunistic pathogen, indicated a significant diminution of almost 40% of the bacterial accumulation on glycosidic surfaces with respect to initial surface. This activity was further compared with a surface presenting a simple hydroxyl residue. Exploration of specific interactions through Lectin A deficient Pseudomonas aeruginosa mutant strain provided new evidences that Lectin A was involved in biofilm maturation, rather than bacterial attachment. Subsequently, the determination of surface free energy and the adhesion free energy between surfaces and bacterial cell wall showed that the adhesion was thermodynamically unfavourable.

Deprotometalation-iodolysis and computed CH acidity of 1,2,3- and 1,2,4-triazoles. Application to the synthesis of resveratrol analogues.

1-Aryl- and 2-aryl-1,2,3-triazoles were synthesized by N-arylation of the corresponding azoles using aryl iodides. The deprotometalations of 1-phenyl-1,2,3-triazole and -1,2,4-triazole were performed using a 2,2,6,6-tetramethylpiperidino-based mixed lithium-zinc combination and occurred at the most acidic site, affording by iodolysis the 5-substituted derivatives. Dideprotonation was noted from 1-(2-thienyl)-1,2,4-triazole by increasing the amount of base. From 2-phenyl-1,2,3-triazoles, and in particular from 2-(4-trifluoromethoxy)phenyl-1,2,3-triazole, reactions at the 4 position of the triazolyl, but also ortho to the triazolyl on the phenyl group, were observed. The results were analyzed with the help of the CH acidities of the substrates, determined in THF solution using the DFT B3LYP method. 4-Iodo-2-phenyl-1,2,3-triazole and 4-iodo-2-(2-iodophenyl)-1,2,3-triazole were next involved in Suzuki coupling reactions to furnish the corresponding 4-arylated and 4,2'-diarylated derivatives. When evaluated for biological activities, the latter (which are resveratrol analogues) showed moderate antibacterial activity and promising antiproliferative effect against MDA-MB-231 cell line.