Charge, polysaccharides

Most frequently, SEC with dextran-, pullulan-, or polystyrene calibration standards has been used to characterize the molecular properties of xylans. However, as for viscometric studies [108], a sufficient solvent ionic strength is a prerequisite for useful SEC measurements of charged polysaccharides, including glucuronoxylans [111-113]. An advantage of the SEC technique is that the presence of protein and phenolic components or oxidative changes can be detected by simultaneous ultraviolet (UV) detection. 

The 5 and 520,w obtained from Eqs. 1-3 will be apparent values because of the effects of solution non-ideality, deriving from co-exclusion and—for charged polysaccharides—polyelectrolyte effects [30]. To eUminate the effects of non-ideality it is necessary to measure either s or S2o,w for a range of different cell loading concentrations c, and perform an extrapolation to zero concentration. For polysaccharides this has been conventionally achieved from a plot of I/5 (or 1/S20,w) versus c [30] ... 

In a typical equilibrium dialysis study of charged polysaccharides an indicator ion, L (chromate), is included in the supporting electrolyte medium (phosphate buffer, pH 6.8, I 0.08) to allow assessment of the effective net charge of the polyanions via a modified form of Eq. 31, namely. 

Charged polysaccharides can also serve as templates for the growth of metallic, semiconductor and magnetic nanoparticles. For instance, chitosan has been reported as a catalyst and stabilizing agent in the production of gold nanoparticles by the reduction oftetrachloroauric (III) acid by acetic acid. The biopolymer controls the size and the distribution of the synthesized Au nanoparticles and allows the preparation... 

Figure 8.15 Cartoon showing how proteins, polysaccharides and surfactants (emulsifiers) might be distributed at the triglyceride-water interface. Inter-facial complexation in vivo between adsorbed protein and charged polysaccharide in the gastrointestinal tract could affect digestion of protein and fat by forming structures that inhibit the accessibility and activity of enzymes (proteases and lipases). Reproduced from Dickinson (2008) with permission.

The interaction with polysaccharides closely related structurally to galactomannans has been studied less for Xanthomonas polysaccharide than for agar. No interaction is observed between Xanthomonas polysaccharide and sodium O-(carboxymethyl)-cellulose (degree of substitution 0.7), probably because of electrostatic repulsion between the two negatively charged polysaccharides.178 Xanthomonas polysaccharide can, however, interact with polysaccharides based on /3-l>(l — 4)-linked D-glucan backbones, as... 

The ideal surface for contact with human blood is the surface of blood vessels, and the immediate surface contains heparinoid complexes. Heparin, a negatively charged polysaccharide, has been bonded to silicon rubber and other polymers. In one procedure, a quaternary ammonium compound is first adsorbed on die polymer substrate and heparin is 111 turn adsorbed on the positively charged surface. Chemical bonding of heparin has also been achieved. Such surfaces do not cause clotting of contacted blood. 

Hayes and Swift (1978), Theng (1979), and Clapp et al. (1991,2005) have dealt in depth with the adsorption of neutral and charged polysaccharides by clays. 

A natural SP OKU-40 was extracted from the marine microalga Dinoflag-ellata and was found to inhibit the replication of HIV, RSV, influenza A and B viruses, measles virus, and parainfluenza viruses type 2 (PIV-2). However, it did not inhibit the replication of mumps virus or PIV-3 [98]. The action of negatively charged polysaccharides is not merely one of nonspecific inhibition of the binding of an enveloped virus to receptors. In fact, OKU-40 did not inhibit the binding of HIV or influenza A virus to the cell membrane, but it did inhibit the fusion of the membranes of HIV-infected MOLT-4 cells to those of uninfected cells and the fusion of the influenza A virus envelope to uninfected MDCK cells [99]. 

The large dimensions necessary for biological responses to weak microwave fields might be achieved by a cooperative reaction of a number of cells or macromolecules to the microwave stimulus, which increases the effective size of the structure and correspondingly reduces the threshold that is required for an effect. Adey suggested that such cooperativity might be induced in the counterions loosely bound near membrane surfaces which contain a loose frame work of charged polysaccharides (32). 

Given the charge, polysaccharide polyanions are electrically conducting in sols and gels, and move in an electrical field (electrophoresis) in compliance with the equation... 

Infrared spectroscopy (IR) exploits the absorption of infrared radiation in the 400-4000-cm 1 segment of the radiation spectrum. IR is a generally useful method to help elucidate organic chemical structures (Barker et al., 1956), including the identification of ionizable groups. Thus, IR spectroscopy is an indirect means of detecting charge. Polysaccharides are best examined... 

Two "non-effects" of conjugation may also be mentioned briefly. In no case does carbohydrate attachment markedly affect the pH-activity relationship of any of the enzymes we have conjugated. This observation is not surprising since we have always conjugated enzymes with uncharged polysaccharide. It remains to be determined whether attachment of an enzyme to a charged polysaccharide affects its pH optimum. 

M. Duckworth and W. Yaphe, The structure of agar. Part II. The use of a bacterial agarase to elucidate structural features of the charged polysaccharides in agar, Carbohydr. Res., 16 (1971) 435-445. 

Felt, O., Baeyens, V., Buri, E, and Gurny, R. (2001), Delivery of antibiotics to the eye using a positively charged polysaccharide as vehicle, Aaps Pharmsci, 3(4), E34. 

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