Sodium, complex with polysaccharides

Alkali-earth metals (calcium, barium, and magnesium) complex with polysaccharides extensively (Reisenhofer et al., 1984). Calcium has a smaller atomic and ionic radius than does sodium and, because it has two valence electrons, it is endowed with greater polarizing and bonding ability than Na+. Ca and Ca2+ easily form insoluble complexes with oxygenated compounds. Polysaccharide salts of alkali-earth metals are generally insoluble. 

The action of chlorine in alkaline media is much slower than that of bromine. Lewin29 reported that the rate of oxidation of D-glucose at pH 9.8 by hypobromite is 1360 times higher than that by hypochlorite at the same pH. For cellulose, the ratio is much smaller (33 to 1). The complexity of the latter system is, however, revealed by the variability of this ratio over the pH range of 8-13 at pH 6-7, the action of hypochlorite is actually slightly faster than that of hypobromite. Maltodextrins and starch have been oxidized with alkaline sodium hypochlorite. The resulting oxidized polysaccharide formed stable complexes with calcium cations.30... 

Amylose is a unique polysaccharide which forms a helical blue-coloured complex with iodine (I5). It also forms helical complexes with a variety of organic compounds such as 1-butanol, 1-pentanol, cyclohexanol, SDS etc. The interaction of SDS, a competing ligand with iodine (I ) complexes of amylose and amylopectin is studied spectrophotometrically. It is observed that the reduction in absorbance at 640 nm accompanied by the blue shift (640-570 nm) in the absorption spectrum is governed by the sequence of addition of the reagents, implying that this Interaction is closely associated with the coil—>hellx transition of the polymer chain. Perturbation of this complex with sodium thiosulphate and urea has revealed that the transition from helix—>coil is rather sluggish and hydrophobic interactions play an important role in the stability of this complex. 

Figure 4.17 shows key aspects of phase behavior of the system water (H20)/Ci4 tiimethylammonium bromide/hyaluronan (an anionic polysaccharide) as a function of added sodium bromide (NaBr) (Lindman and Thalberg, 1993). With no added salt, a region with two liquid phases is seen for a range of surfactant polymer ratios. One phase is rich in both polymer and surfactant. The phase separation stems from complexation with a low net charge on each polymer chain, as discussed above. As salt is added, the eharges on both surfactant and... 

Anionic polysaccharides respond in similar fashion to surfactants. They are relatively unaffected by anionic surfactants like sodium or ammonium lauryl sulfate. On the other hand, they form strong ionic complexes with cationic surfactants like dodecyltrimethylam-monium chloride, even at cationic surfactant concentrations below the critical micelle concentration (cmc), or concentration at which the surfactant molecules form micelles in solution (92,93). The behavior of polyelectrolytes in the presence of surfactants is summarized in Chapter 5 and has been reviewed (94). 

Figure 10.3 Antibody molecules oxidized with sodium periodate to create aldehyde groups on their polysaccharide chains can be modified with PDPH to produce thiols after reduction of the pyridyl disulfide. Direct labeling of the sulfhydryls with "Tc produces a radioactive complex.

Figure 7.16 Dependence on tlie polysaccharide concentration CDS of (a) tlie second virial coefficient A2 and (b) tlie stmcture-sensitive parameter p of complexes of sodium caseinate + dextran sulfate , complexes prepared in bulk solution a, complexes prepared at tlie interface in a protein-stabilized foam , sodium caseinate alone. Reproduced from Semenova et al. (2009) with permission.

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