Band 95, Heft 9

Owing to the relevance of fluorescently labeled carbohydrates in the study of biological processes, we have investigated several routes for the preparation of saccharides covalently linked to borondipyrromethene (BODIPY) fluorophores. We have shown that BODIPY dyes can be used as aglycons through synthetic saccharide protocols. In particular, a per-alkylated 8-(2-hydroxy-methylphenyl)-4,4′-dicyano-BODIPY derivative, which withstands glycosylation and protection/deprotection reaction conditions without decomposition, has been used in the stepwise synthesis of two fluorescently labeled trisaccharides. These saccharides displayed high water solubility and a low tendency to (H-)aggregation, a phenomenon that causes loss of photophysical efficiency in BODIPYs. Two additional synthetic strategies toward glyco-BODIPYs have also been described. The first method relies on a Ferrier-type C -glycosylation of the BODIPY core, leading to linker-free carbohydrate–BODIPY hybrids. Secondly, the application of the Nicholas propargylation reaction to 1,3,5,7-tetramethyl BODIPYs provides access to 2,6-dipropargylated BODIPYs that readily undergo CuAAC reactions with azido-containing sugars. From a photophysical standpoint, the BODIPY-labeled saccharides could be used as stable and fluorescent water-soluble chromophores, thereby addressing one of the current challenges in molecular imaging.

d -Arabinofuranosidases (Ara f ases) degrade the arabinan in the cell wall of acid-fast bacteria like Mycobacterium. Synthetic arabinan fragment probes could be used to investigate the function of d -Ara f ases, whose synthetic studies had been reported previously. The homologue of one of the arabinan-degrading enzymes, exo-α- d -Ara f ase, was identified as BBDE_2040 from Bifidobacterium dentium . BBDE_2040, which is a homologue of α- d -Ara f ase, was also observed to hydrolyze α- d -fructofuranosides (Fru f ), whose linkage is found in food. In this paper, we present synthetic studies and structural analysis of the α- d -Ara f and α- d -Fru f derivatives as substrates and products of the enzymatic reaction for a thorough examination of BBDE_2040. The results indicated that BBDE_2040 is a glycoside hydrolase (GH) family 172 difructose dianhydride I synthase/hydrolase and an anomer-retaining GH.

We have disclosed that 3,5-dimethyl-4-(2′-phenylethynylphenyl)phenyl (EPP) glycosides could be employed as glycosylation donors via an unprecedented activation mechanism. Here we report that the EPP glycosides without the 3,5-dimethyl groups, which were previously installed to prevent the plausible Friedel-Crafts-type side reactions, can also undergo glycosylation effectively. Employing such an EPP 2-azidoglucoside as donor, the construction of the challenging α-GlcN-(1→4)-GlcA linkage is realized, leading to a heparin trisaccharides precursor.

Glycosphingolipids (GSLs) in the mammalian plasma membrane are essential for various biological events that occur on cell membranes by forming glycolipid-rich membrane domains, such as lipid rafts. Lactosylceramide (LacCer) forms a highly ordered phase in model and biological membranes. However, the details of this domain remain unclear. We examined the dynamic assembly of LacCer in cholesterol-containing phase-separated membranes by fluorescence imaging and solid-state NMR. Solid-state 2 H NMR of the deuterated LacCer probes in the membranes indicated that the potent LacCer–LacCer interaction significantly reduced the incorporation of cholesterol in the LacCer domains. Moreover, increasing the amount of cholesterol induced the formation of nanometer-scale LacCer domains, which can be biologically relevant. The lateral interaction of ganglioside GM3 with the epidermal growth factor receptor (EGFR) transmembrane segment was examined using fluorescence spectroscopy under membrane conditions. Lateral FRET between the NBD fluorophore on the EGFR transmembrane segment and the ATTO594 fluorophore on the GM3 head group suggested that GM3 interacts with the transmembrane segment and partially inhibits the EGFR dimerization by stabilizing the peptide monomer. More precise investigations of GSL–GSL and GSL-protein interactions occurring in membrane environments can lead to the elucidation of the cellular functions of GSL from structural points of view.

Ovine pneumonia is a disease in sheep that is associated with major animal welfare issues and economic losses and for which there is no effective vaccine. We tested the adjuvanticity of our most promising α,α′-trehalose 6,6′-glycolipids, lipidated brartemicin adjuvants p -C18Brar ( 3 ), o -C18Brar ( 4 ), and amide-TDB ( 5 ) in vaccines for ovine pneumonia containing Mannheimia haemolytica and Mycoplasma ovipneumoniae whole cell antigens. p -C18Brar ( 3 ) and o -C18Brar ( 4 ) led to strong antigen-specific IgG antibody titres that were better than those elicited by the prototypical α,α′-trehalose glycolipid trehalose dibehenate (TDB, 2 ) and amide-TDB ( 5 ). T-cell responses, as determined by measuring IFN-γ and IL-17A production from antigen-stimulated whole blood cultures, revealed that p -C18Brar ( 3 ), but not TDB ( 2 ), o -C18Brar ( 4 ), or amide-TDB ( 5 ), led to statistically significant increases in these cytokines. We then optimised the synthesis of p -C18Brar ( 3 ) (3 steps, 72 % overall yield) and undertook further vaccination studies to determine the optimal dose of p -C18Brar ( 3 ) that would be used for future large scale ovine pneumonia field trials. At a dose of 3.75 mg per vaccine, the adjuvanticity of p -C18Brar ( 3 ), as measured by levels of anti- M. haemolytica IgG antibody and T-cell responses (IFN-γ and IL-17A) was better than that elicited by the commercially available adjuvant Quil-A, and had reduced reactogenicity. Taken together, the excellent immunological profile of p -C18Brar ( 3 ) and its ease and efficiency of synthesis makes it an attractive adjuvant for use in veterinary vaccines.

Currently, the agricultural sector is responsible for the contamination of groundwater and springs due to the excessive use of pesticides, which represents a risk to human and environmental health. Among pesticides, glyphosate is the most used herbicide to increase agricultural production, however, it can cause intoxication in humans and has been classified as a potentially carcinogenic agent. Alternatives for removing these contaminants from water have been studied and discussed, including biosorption, a physical-chemical process that removes substances from solutions using a natural and renewable material. In this sense, this work studied the process to obtain cationic cellulose microfibers (cCMF) from sugarcane bagasse residue, by cellulose isolation followed by cationization reaction with Girard T reagent to promote a new adsorbent for glyphosate removal from water. It was observed that cCMF structure maintains the fibrillar morphology after the microfiber production (1.375 mmol g −1 oxidation degree). Results of zero charge of cCMF microfibers showed an isoelectric point pH = 5.4 ± 0.016 and the highest adsorption capacity was reached at pH 14 (59.21 %), showing a clear pH dependence on the adsorption process. Thereby, the cCMF can be produced from sugarcane bagasse residue being applied as a potential biomaterial for removing organic compounds from water.

Glycovesicles mimic synthetic cell membrane surfaces and aid to delineate intricate, weak carbohydrate–protein interactions. In this report, the dependence of the hydrodynamic diameters in relation to the molar fractions of carbohydrate moieties in the mixed polydiacetylene (PDA) glycovesicles is evaluated. The glycovesicles are constituted with diacetylene monomers of varying molar fractions of carbohydrate moieties and the hydrodynamic diameters are assessed without and with polymerization of the vesicles. A strong dependence of the hydrodynamic diameter of glycovesicles is seen as a function of the molar fractions and the nature of the sugar moiety being either mono- or disaccharide. A monotonous increase in the hydrodynamic diameters of the glycovesicles occurs with the increase in mole fractions of the sugar monomer lipids. Upon polymerization, the hydrodynamic diameters reduce for the vesicles with lower mole fractions of sugar monomer, whereas the reverse occurs for glycovesicles possessing higher mole fractions. Disaccharide glycovesicles possess higher hydrodynamic diameters than monosaccharide-containing vesicles. Ligand–lectin interactions were probed with lactose disaccharide-containing glycovesicles with tetrameric peanut agglutinin lectin, from which an increase in the hydrodynamic diameters is observed, as the mole fraction of sugar monomer is increased in the PDA-glycovesicles.

Glutamine:fructose-6-phosphate amidotransferase (GFAT) is the rate-limiting enzyme of the hexosamine biosynthetic pathway (HBP), an important route for de novo synthesis of amino sugars, which are key components of prokaryotic cell walls, chitin, and complex eukaryotic glycoconjugates. GFAT also plays a major role in several pathological processes, including cancer and diabetes. It has been 60 years since GFAT was first characterized. During this time, the knowledge about the enzyme’s mechanisms and biological relevance has increased considerably. We take the anniversary of GFAT’s discovery as an opportunity to discuss the role of GFAT in both health and disease and explore its biotechnological potential as a target for antimicrobial and anticancer chemotherapy.