PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “POLYSACCHARIDES, BACTERIAL”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources
PubMed1979

Conformational investigation on the bacterial polysaccharide xanthan.

The conformation of xanthan has been investigated as a function of temperature, ionic strength, and polymer concentration. A reversible transition induced by temperature is demonstrated; the melting temperature (TM) is directly correlated to the total ionic-strength and is independent of the polymer concentration. Measurements of circular dichroism show that the polysaccharide exists in a combination of only two characteristic conformations (random and ordered), regardless of the temperature and the concentrations of salt and polymer. Hydrodynamic measurements show that the hydrodynamic volume of both conformations is almost constant over the range of temperature investigated. The mechanism proposed by Morris for melting is confirmed, and a multichain process is excluded. The birefringence stability of the concentrated solutions is discussed.

Carbohydrate Conformation↗
PubMed1983

Immunochemical studies on Shigella dysenteriae type 9 bacterial polysaccharide.

On graded hydrolysis and Smith degradation, the O-somatic polysaccharide isolated from Shigella dysenteriae type 9 bacteria, strain NCTC 7919, yielded five oligosaccharides which were characterized. The positions of the O-acetyl and pyruvic acetal groups in the repeating unit were identified. Immunochemical studies indicated that D-galactose is the immunodominant sugar in the polysaccharide, and one of the oligomers, having the structure Gal-(1 leads to 3)-GlcNAc-(1 leads to 3)-Gal-(1 leads to 4)-Man, showed maximum inhibition of the homologous precipitation.

Antigen-Antibody Complex↗
PubMed1983

Immunochemical studies on Shigella dysenteriae type 10 bacterial polysaccharide.

On graded hydrolysis and Smith degradation, the O-somatic polysaccharide isolated from Shigella dysenteriae type 10 bacteria yielded four oligosaccharides which were characterized by methylation studies. Immunochemical studies using constituent monosaccharides and the oligosaccharides indicated that the sugar grouping leads to 3)-ManNAc-(1 leads to 3)-Rha-(1 leads to 4)-GlcNAc-(1 leads to was the immunodominant part in the polysaccharide molecule, and that 2-acetamido-2-deoxy-D-mannose contributed maximally to the immunological specificity of the macromolecule.

Carbohydrate Conformation↗
PubMed1992

On the solution properties of bacterial polysaccharides of the gellan family.

The influence of side chains and substituents on the polyelectrolyte behaviour of aqueous solutions of polysaccharides of the gellan family has been studied. The results of conductimetric and potentiometric titrations suggest that each of these polysaccharides adopts a double-helix conformation. Deacetylation destabilises the helix of rhamsan and gellan, and optical rotation data confirm these results. The side chain in rhamsan is more flexible and is remote from the carboxylate groups, and the behavior of this polysaccharide is similar to that of gellan. Gelation of deacetylated rhamsan occurs in the presence of calcium ions. The intrinsic viscosity as a function of ionic strength depends on the structure of the polysaccharide and on the presence of acetyl groups.

Carbohydrate Conformation↗
PubMed1992

Synthesis and preliminary characterisation of new esters of the bacterial polysaccharide gellan.

Under the appropriate experimental conditions, ethyl, propyl, and methylprednisolon-21-yl esters of gellan can be obtained without significant degradation. At low degrees of esterification (de), depending on the ester moiety, the products are water-soluble, which allows the influence of hydrophilicity and charge density on their ability to assume an ordered conformation in dilute aqueous solution to be studied. With high de, the products were soluble only in organic solvents (e.g., methyl sulphoxide) with good film-forming capacity. The methylprednisolon-21-yl esters have been characterised in a preliminary manner in terms of drug-release kinetics.

Alcohols↗
PubMed1994

O-acetylation affects the binding properties of the carboxyl groups on the Vi bacterial polysaccharide.

The capsular polysaccharide of Salmonella typhi and Citrobacter freundii (Vi) is a linear homopolymer of (1-->4)-linked 2-acetamido-2-deoxy-alpha-D-galactopyranosyluronic acid partially O-acetylated at the C-3 position. The physico-chemical properties of the carboxyl groups of the Vi polysaccharide, as a function of different degrees of O-acetylation, were studied by potentiometric titration, circular dichroism, and their reaction with the bulky nucleophile 2-nitro-phenylhydrazine (NPH). Potentiometric titrations with K+ and Ca2+ hydroxides showed that the difference in the free energy of binding between the two cations (delta GKCa) was inversely proportional to the degree of O-acetylation. Similar cationic effects were found when measuring circular dichroism. Moreover there was also an inverse relation between the degree of O-acetylation and the extent of binding of NPH to the carboxyl groups. These data all indicate that O-acetyl groups hinder the association of carboxyls with cations and nucleophilic reagents. This provides a possible explanation for the importance of the O-acetyl and the relative unimportance of the carboxyl groups in contributing to the immunologic properties of the Vi.

Acetylation↗
PubMed2003

Characterisation of bacterial polysaccharides: steps towards single-molecular studies.

Techniques used in studies of polysaccharides, including chemical composition, linkage pattern, and higher order structures are in constant development. They provide information necessary for understanding of the polysaccharide properties and functions. Here, recent advancements in studies of the polysaccharides at the single-molecule level are highlighted. Over the last few years, single-molecule techniques such as force spectroscopy have improved in sensitivity and can today be used to detect forces in the pN range. In addition, these techniques can be used to investigate properties of single molecules close to physiological conditions. The challenges in the interpretation of the observations are aided by control experiments using well-characterised polysaccharides and by data provided by complementary methods. This field is expected to have increasing impact on the further advancement of the molecular understanding of the role of polysaccharides in various biological processes such as recognition and cell adhesion.

Biochemistry↗
PubMed1983

Visualization of bacterial polysaccharides by scanning transmission electron microscopy.

Highly purified capsular polysaccharides of Neisseria meningitidis groups A, B, and C have been visualized by high resolution Scanning Transmission Electron Microscopy (STEM). Spheroidal macromolecules approximately 200 A in diameter are characteristic of the Meningococcus A and C polysaccharides whereas filaments that are 400-600 A in length are found in Meningococcus B polysaccharide preparations. Filaments are occasionally found associated with the spheroidal Meningococcus A and C polysaccharides and it is proposed that these structures are composed of a long (1-4 microns) filament or filaments that are arranged in spheroidal molecules or micelles of high molecular weight. The Meningococcus B polysaccharide, by contrast, is a short flexuous filament or strand of relatively low molecular weight. A relationship between morphology and antigenicity is proposed.

Freeze Drying↗