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At least 343 records · Page 19Linked to original sources
PubMed2001

Ultraweak sugar-sugar interactions for transient cell adhesion.

Carbohydrate-carbohydrate interactions are rarely considered in biologically relevant situations such as cell recognition and adhesion. One Ca(2+)-mediated homotypic interaction between two Lewis(x) determinants (Le(x)) has been proposed to drive cell adhesion in murine embryogenesis. Here, we confirm the existence of this specific interaction by reporting the first direct quantitative measurements in an environment akin to that provided by membranes. The adhesion between giant vesicles functionalized with Le(x) was obtained by micropipette aspiration and contact angle measurements. This interaction is below the thermal energy, and cell-cell adhesion will require a large number of molecules, as illustrated by the Le(x) concentration peak observed at the cell membranes during the morula stage of the embryo. This adhesion is ultralow and therefore difficult to measure. Such small interactions explain why the concept of specific interactions between carbohydrates is often neglected.

Calcium↗
PubMed1976

An approach to the synthesis of branched-chain amino sugars from C-methylene sugars.

The reaction of 1,2:5,6-di-O-isopropylidene-3-C-methylene-alpha-D-ribo-hexofuranose (4) with mercuric azide in hot 50% aqueous tetrahydrofuran yielded, after reductive demercuration, 3-azido-3-deoxy-1,2:5,6-di-O-isopropylidene-3-C-methyl-alpha-D-glucofuranose (5). Partial, acid hydrolysis of 5 afforded the diol 7, which gave 3-azido-3-deoxy-1,2-O-isopropylidene-5,6-di-O-methanesulphonyl-3-C-methyl-alpha-D-glucofuranose (8) on sulphonylation. On hydrogenation over a platinum catalyst and N-acetylation, the dimethanesulphonate 8 furnished 3,6-acetyleprimino-3,6-dideoxy-1,2-O-isopropylidene-5-O-methanesulphonyl-3-C-methyl-alpha-D-glucofuranose (9), which was also prepared by an analogous sequence of reactions on 3-azido-3-deoxy-1,2-O-isopropylidene-5-O-methanesulphonyl-3-C-methyl-6-O-toluene-p-sulphonyl-alpha-D-glucofuranose (13). The formation of the N-acetylepimine 9 establishes the D-gluco configuration for 5. 1,2-O-Isopropylidene-3-C-methylene-alpha-D-ribo-hexofuranose (20) reacted with mercuric azide in aqueous tetrahydrofuran at approximately 85 degrees to give 3,6-anhydro-1,2-O-isopropylidene-3-C-methyl-alpha-D-glucofuranose (22) as a result of intramolecular participation by the C-6 hydroxyl group in the initial intermediate.

Chemical Phenomena↗
PubMed1982

Calorimetric analysis of sugars and sugar derivatives with aid of an enzyme thermistor.

Enzymic determination of L-ascorbic acid, D-galactose, D-glucose, cellobiose, lactose, and sucrose with an enzyme thermistor is described. The enzyme thermistor is a simple flow-calorimeter designed for routine analysis and measures metabolites by the heat produced in a small column with immobilized enzyme. This instrument may be used for determination of discrete samples as well as for continuous monitoring. As the change of enthalpy produced by the primary reaction is usually large enough to make the measurement sufficiently accurate, simple assay procedures can be designed, an advantage of great importance when the samples are crude and complex.

Ascorbate Oxidase↗
PubMedDate not supplied

Gluconacetobacter diazotrophicus, a sugar cane endosymbiont, produces a bacteriocin against Xanthomonas albilineans, a sugar cane pathogen.

Gluconacetobacter diazotrophicus in liquid culture secretes proteins into the medium. Both medium containing Gluconacetobacter protein and a solution of this protein after acetone precipitation appeared to inhibit the growth of Xanthomonas albilineans in solid culture. This apparent inhibition of bacterial growth has, in fact, been revealed to be lysis of bacterial cells, as demonstrated by transmission electron microscopy. Fractionation of the Gluconacetobacter protein mixture in size-exclusion chromatography reveals a main fraction with lysozyme-like activity which produces lysis of both living bacteria and isolated cell walls.

Acetobacteraceae↗