PubMed · 4592777
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O Nordland. 1973-11-12. [Shock lung].. https://pubmed.ncbi.nlm.nih.gov/4592777/
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Recently, branching sucrases encoded in the genomes of certain Lactic Acid Bacteria (LAB) strains have become novel enzymes to obtain branched α-glucans. In this study an active α-(1 → 2) branching sucrase from Apilactobacillus kunkeei PDER37 was expressed, characterised and distinct branched dextrans was obtained with reactions under different sucrose: dextran ratio. Structural characterisation by 1H and 13C NMR analysis demonstrated the branching of the dextran with (1 → 2)-linked α-d-glucose units with no alteration in the final structure depending on sucrose: dextran ratio (D0) but this ratio was effective for the determination of the molecular weights of the branched dextrans (D1, D2 and D3). FTIR analysis further supported the dextran structures and suggested the higher accumulation of the α-Glc units in the branched dextrans. Thermal characterisation of the branched dextrans obtained by TGA and DSC analysis suggested the increased hygroscopicity of the branching units. Both SEM and AFM analysis demonstrated more porous chain like structures in the branched dextrans. This study provides valuable information on the role of active α-(1 → 2) branching sucrase (BS37) for the production of branched dextrans with potential increased physicochemical status applicable for food and other industries.
A novel procedure to prepare dextran microspheres, without the use of organic solvents was developed. The method is based on phase separation which occurs in aqueous solutions of PEG and methacrylated dextran (dexMA). After stirring this two phase system a water-in-water emulsion is formed. When dexMA forms the discontinuous phase, dextran microspheres can be obtained by polymerization of the methacryloyl groups attached to dextran. The aim of this study was to gain insight into the formulation parameters that affect the particle characteristics. Therefore, it was necessary to establish dexMA/PEG/water phase diagrams. Lower polymer molecular weights and higher degrees of MA substitution resulted in less pronounced phase separation (binodal shifts to higher concentrations). The volume weight mean microsphere diameter varied between 2.5 and 20 microm, depending on the viscosities of both phases and the PEG/dexMA volume ratio. A more viscous continuous phase and/or a less viscous discontinuous phase resulted in smaller microspheres. Furthermore, the particle size increased with decreasing PEG/dexMA volume ratios. The particle characteristics, like cross-link density, initial water content and size can be tailored by adjusting the formulation parameters.
Bacterial polysaccharides, including capsular polysaccharides, are poor immunogens particularly in young infants. However, conjugation of bacterial polysaccharides to immunogenic carrier proteins generally results in conjugates that induce strong antipolysaccharide T-helper-cell dependent immune responses, also in young infants. The magnitude of the response and the extent of the T-helper-cell dependency is related to the chemical characteristics of the particular conjugate such as presence or absence of polysaccharide-protein cross-linking, presence or absence of spacer arms, character of spacer arms, type of carrier protein, size of conjugated polysaccharide hapten and molar degree of substitution. In the present study a new, general and simple method for the preparation of poly- and oligosaccharide-protein conjugates is presented. This new method is based on spacer-introducing chemistry that allowed for conjugation of a model polysaccharide, dextran, ranging in size from 0.5 to 150 kDa, to tetanus toxoid (TTd). The developed conjugation method involves derivatization of polysaccharide with 2-iminothiolane (2-IT) and activation of carrier protein, such as TTd, with N-hydroxysuccinimide ester of bromoacetic acid. Reaction rates and accordingly the substitution of the conjugates, could be controlled by varying time, pH and concentration of the reactants. Unlike direct reductive amination, the 2-IT based conjugation technology is fast and made it possible to couple fairly large polysaccharides to TTd.