Individual Polysaccharides

Standardization and Testing". The Center for Biologies Evaluation and Research has set guidelines for the vaccine which include standards for si2e of the individual polysaccharides and specifications for both purity (absence of protein and nucleic acid) and chemical and immunological identity. 

In dimorphic fungi, the composition of constituent polysaccharides is sensitive to morphology and to the cultural conditions. These effects are accentuated in the case of Sporothrix schenckii, and 13C-n.m.r. spectroscopy can be used to detect individual polysaccharides in a qualitative way. The 13C-n.m.r. spectra of mannose-containing polysaccharides of ten Sporothrix schenckii and three Ceratocystis stenoceras species, grown under various conditions, were distinguishable in terms of the presence of signals,130 at 8C 103.3 to 103.7, which arose from 0-a-L-rhamnopyranosyl-(l- 2)-0-a-L-rhamnopyranosyl-(1— 3)-side-chains (14 C-l, 103.7 C-l, 96.8), and were not present in... 

Lamport40 considered the primary cell-wall to be a single, bagshaped macromolecule having a coherent, cross-linked structure, with bonds both between the hydroxy-L-proline-rich, wall protein extensin and wall polysaccharides, and between individual polysaccharides. 

The dimensions of the xylan unit cell are slightly different a = b = 1.340 nm, (fibre axis) = 0.598 nm.) Atkins and Parker T6) were able to interpret such a diffraction pattern in terms of a triple-stranded structure. Three chains, of the same polarity, intertwine about a common axis to form a triple-strand molecular rope. The individual polysaccharide chains trace out a helix with six saccharide units per turn and are related to their neighbours by azimuthal rotations of 2ir/3 and 4ir/3 respectively, with zero relative translation. A similar model for curdlan is illustrated in Figure 6. Examinations of this model shows that each chain repeats at a distance 3 x 0.582 = 1.746 nm. Thus if for any reason the precise symmetrical arrangement between chains (or with their associated water of crystallization) is disrupted, we would expect reflections to occur on layer lines which are orders of 1.746 nm. Indeed such additional reflections have been observed via patterns obtained from specimens at different relative humidity (4) offering confirmation for the triple-stranded model. 

A few pyrolysis studies done on yeasts and yeast-like fungi did not attempt to analyze individual polysaccharides but to obtain a fingerprint characterization [67], It was also common to use statistical techniques such as factor analysis for the data interpretation. It was not unusual to find N-acetylamino sugar units in fungal polysaccharides. These units showed characteristic peaks in Py-MS that allowed the distinction of different materials. 

In the limiting case of very dilute concentration (cq), close to ideal conditions, interaction between polysaccharide molecules may be considered negligible, and material qualities are primarily correlated with isolated and independent conformations and dimensions of individual polysaccharide molecules. 

Modification of the atomic force microscope with feedback loops enabled force-extension curves for individual polysaccharide molecules to be measured under constantly increasing force (rather than constant displacement), in a nanoscale version of the INSTRON tester for measuring paper strength. ... 

A variety of monomers such as glucose, galactose, etc., and linkage positions such as 1- 2, 1 3, 1- 4, etc., can have anomeric forms such as a or j3, with a degree of branching which leads to an extraordinary variety of primary structures for polysaccharides. The secondary structure of an individual polysaccharide is defined by a set of torsion angles , [Pg.891]

Polysaccharides contain as few as 10 or as many as several thousand monosaccharide units joined together by glycosidic linkages. The molecular weight of the individual polysaccharide chains is variable. The most common polysaccharides are starch and cellulose. 

Our approach to these and similar question has been to investigate the mechanisms by which pure cultures of colon bacteria utilize individual polysaccharides in vitro, with a view to determining what factors affect the organism s decision to utilize a particular type of carbohydrate. This approach is based on the assumption that information about the specific features and limitations of polysaccharide-catabolizing systems in colon bacteria will permit us either to make predictions about the extent to which catabolism of a particular class of polysaccharides can occur in vivo or to develop specific methods for detecting metabolic states in bacteria in vivo. 

A concentration gradient of NaCI/KCl-based eluent moves the polysaccharide molecules bound to diethylaminoethane exchange column leading to their separation based on their net charge. The strength of interaction between the polysaccharide molecules and the ionic column depends on the net charge on individual polysaccharide molecules and hence elute at differing chloride ion concentrations [95]. 

Glycosaminoglycans, solubilized from articular cartilage and synovial fluid by proteolysis, have been separated by electrophoresis, allowing microgram quantities of individual polysaccharides to be detected. i e electrophoretic separation of glycosaminoglycans in cationic media may not represent a normal electrophoresis but has more in common with phenomena that are associated with electrofocusing techniques. Caution in interpreting data from this and similar electrophoretic techniques has ben advocated. ... 

These properties and their utilization in food products are described in more detail in section 4.4.4, where individual polysaccharides are covered. Here, only a brief account will be given to relate their properties to their structures in a general way. 

The addition of two ether-forming reagents will often give products with completely new properties, compared with the individual polysaccharide ethers, or compared with a physical mixture of the two polysaccharide ether derivatives [8]. 

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