Polysaccharides experimental

Two helices are packed antiparallel in the orthorhombic unit cell. Association of the helices occurs through a series of periodic carboxylate potassium water - carboxylate interactions. An axial projection of the unit-cell contents (Fig. 23b) shows that the helices and guest molecules are closely packed. This is the first crystal structure of a polysaccharide in which all the guest molecules in the unit cell, consistent with the measured fiber density, have been experimentally located from difference electron-density maps. The final / -value is 0.26 for 54 reflections, of which 43 are observed, and it is based on normal scattering factors.15... 

Interactions with xanthan were investigated for some GAX fractions of wheat bran [109]. Whereas, for lowly substituted GaMs a synergy in viscosity was observed at low total polymer concentrations, yielding a maximum of the relative viscosity at nearly equal proportions of both polysaccharides [124], the xanthan/xylan mixtures at the same experimental conditions showed no synergy. The observed decrease in the relative viscosity values upon addition of the xylan indicates that a certain interaction with xanthan takes place, but that it leads to a contraction in the hydrodynamic volume. The authors suggested that structural and conformational differences between GaM and GAX might be the reason for this observation. 

The relaxation data for the anomeric protons of the polysaccharides (see Table II) lack utility, inasmuch as the / ,(ns) values are identical within experimental error. Obviously, the distribution of correlation times associated with backbone and side-chain motions, complex patterns of intramolecular interaction, and significant cross-relaxation and cross-correlation effects dramatically lessen the diagnostic potential of these relaxation rates. 

Determination of number o/per/ro/jenZ-exudative cells after i.p. (intraperitoneal) application of polysaccharide fractions and during infection with Y. pseudotuberculosis in experimental animals. 

Fig. 3.5 Representation of a scheme of an experiment (upper set of drawings) and the obtained experimental results presented as AFM images (middle part) and cross-sectional profiles (bottom) that provides evidence of silica nucleation and shell formation on biopolymer macromolecules. Scheme of experiment. This includes the following main steps. 1. Protection of the mica surface against silica precipitation. It was covered with a fatty (ara-chidic) acid monolayer transferred from a water substrate with the Langmuir-Blodgett technique. This made the mica surface hydrophobic because of the orientation of the acid molecules with their hydrocarbon chains pointing outwards. 2. Adsorption of carbohydrate macromolecules. Hydrophobically modified cationic hydroxyethylcellulose was adsorbed from an aqueous solution. Hydrocarbon chains of polysaccharide served as anchors to fix the biomacromolecules firmly onto the acid monolayer. 3. Surface treatment by silica precursor. The mica covered with an acid mono-...

We may return now to the polysaccharides present in the peanut for a brief consideration of the relationship of the other components present in the pectic materials to the araban constituent. All the evidence indicates that the pectic acid portion of the peanut is identical with normal pectic acid and, as was indicated in the previous section, this material, which is very stable to acid hydrolysis and possesses a high positive rotation contains a main chain which is built up of D-galac-turonic acid residues of the pyranose type. If, therefore, the araban associated with the pectic acid had been derived directly from the pectic acid by decarboxylation without intermediate hydrolysis of the poly-galacturonide, the sugar residues in the araban should also be in the pyranose form. The experimental evidence shows clearly, however, that the arabinose residues in araban are furanose in type and it follows that any hypothesis concerning the direct conversion of pectic acid into the araban by decarboxylation is untenable. 

Table I lists physical data for a number of the carbamate and ester derivatives of cellulose, chitin, amylose, amylopectin, and dextran synthesized as described in the Experimental Section. The solubility of the polysaccharide starting materials as well as that of the produced derivatives allows for macromolecular characterization through techniques including UV, NMR, IR, high pressure liquid chromatography, etc.

Indeed, these results are qualitatively similar to those depicted in Figs. 12 and 13, and it is therefore tempting to ascribe them to the presence, on the bacterial cell walk, of polyanionic environments surrounding the sites where lysozyme cleaves the polysaccharide network. However, the point is that, although several authors have concluded from various experimental observations that the cell walls of bacteria such as Escherichia coli and Micrococcus luteus are predominantly negatively charged (Katerakky et al, 1953 Salton, 1964 Davies et al, 1969), the complexity of the bacterial cell wall architecture means that little is known about the... 

---