Polysaccharide ionic

Reid, D. S. (1983). Ionic polysaccharides. In Wilson, A. D. Prosser, H. J. (eds.) Developments in Ionic Polymers-1, Chapter 6. London and New York Applied Science Publishers. 

The zero-shear viscosity r 0 has been measured for isotropic solutions of various liquid-crystalline polymers over wide ranges of polymer concentration and molecular weight [70,128,132-139]. This quantity is convenient for studying the stiff-chain dynamics in concentrated solution, because its measurement is relatively easy and it is less sensitive to the molecular weight distribution (see below). Here we deal with four stiff-chain polymers well characterized molecu-larly schizophyllan (a triple-helical polysaccharide), xanthan (double-helical ionic polysaccharide), PBLG, and poly (p-phenylene terephthalamide) (PPTA Kevlar). The wormlike chain parameters of these polymers are listed in Tables... 

Let us consider now the case of a specific ionic polysaccharide. The unique properties of complexes of the cationic chitosan with non-ionic sorbitan esters provides an interesting example. Grant and co-workers (2006) have established that mixtures of chitosan and surfactant form emulsion-like solutions and/or creams, where the surfactant component is present as droplets or micelle-like particles and the chitosan solution acts as the system s continuous phase. It was established that the length and the degree of saturation of the surfactant hydrocarbon chain have a significant impact on the development of the chitosan-surfactant complexes. Moreover, an optimal distance between the chitosan s protonated amine groups is required for effective interactions to occur between the polysaccharide and the sorbitan esters. 

N 148 "Ionic Polysaccharides. V. Conformational Studies of Hyaluronic Acid, Cellulose, and Lamlnaran"... 

Xanthan gum was shown to be stiffer than CMC and alginate all three are ionic polysaccharides, with CMC having slightly more flexibility than alginate under identical conditions (R. C. Clark, 1992). The invariant nature of xanthan dispersion properties is attributed to the stability of the tertiary structure. The indifference of this gum to salt is explained by its already rigid conformation (Morris, 1976). 

Electrolytes affect dispersed polysaccharides through water inactivation, specific ion binding, and polyanion neutralization. Each effect is valence-dependent, but is less on neutral polysaccharides than on ionic polysaccharides. Di- and polyvalent cations gel or precipitate a constant amount of polysacchride at much lower concentrations than do monovalent cations. The precipitation reaction is used to advantage in isolating pectin with alkaline Al3+, because this cation and polymeric forms of Al(OH)3 readily precipitate and entrain pectinic acid from apple tissue homogenates. Other di- and polyvalent cation effects are crosslinking (Prud homme et al., 1989) and an increased rate of (3 elimination over monovalent cations (Sajjaanan-... 

It used to be thought that cations simply precipitated polyanions, but it was recognized later that electrolytes had special valence and solvent-mediated effects on a hydrosol other than neutralization of opposite charges (Holmes, 1922). It is now firmly established that ionization of the carboxyl and sulfuric acid groups in ionic polysaccharides, or adsorption of ions on neutral macromolecules, is an initial step in electrokinetic mechanisms of stabilization and destabilization. 

The pH and Ionization Constant (K,) of Some Washed, Aqueous Dispersed Ionic Polysaccharides (< 1%)"... 

The identicalness of the ionization sites in a linear polyelectrolyte (Tanford, 1961) stimulated the interest of Walter and Jacon (1994) in a possible relationship between Kz and M of ionic polysaccharides displaying the characteristic titration curve of a weak, monobasic acid. Without any theoretical assumption, Eq. (S.4) was derived from simple algebra by combining elementary principles of the dissociation theory of weak acids with polymer segment theory ... 

As shown in Eqs. (3.9) and (3.10), the concentration of migrating cations is a squared function of the adsorbate concentration in the outer volume of the solution. The Donnan distribution is a source of serious error when determining M of ionic polysaccharides by membrane osmometry. Polyanions may be freed of cations and excess HsO+ by electrodialysis. 

Many naturally occurring ionic polysaccharides are mixed salts of alkali, alkali-earth, and transition metals with different insolubilities. Salts of alkali metals are invariably soluble. Sodium, the most ubiquitous alkali, possesses a single valence electron, large atomic and ionic radii, and very low ionization potential. Na+ hydrates in aqueous solution and retains its coordination water in the solid state. Prior to use, native polysaccharide salts are usually converted to the sodium form whence they acquire functionality. 

The effect of heat on the polysaccharide-water interaction in several dispersions and suspensions was studied by comparative viscometry and rheometry (Tables I-IV). The polysaccharides were the purest manufacturers grade laboratory washed and dried before dispersion. The dispersion concentrations were below c to accommodate capillary viscometry, and the suspension concentrations were above c to accommodate rheometry. It is seen in Tables I and II that the cellulose derivatives made the most stable dispersions and the propylene glycol alginate made the least. Dispersions of the neutral polysaccharides were more stable than those of the ionic polysaccharides. From Tables III and IV, it can be argued that suspensions benefit... 

Pechanek et al. (1982) determined ionic polysaccharides by fl migration through polyacrylamide and agarose gels and on cellulose acetate membranes the polyanions were detected by staining. At the dimensions found in gel micropores, pairs of surfaces create an adsorption potential ( ) 3.5 times that created at the same distance from a single surface (Void and Void, 1983). 

Figure 6 suggests that the viscosity of ionic polysaccharides in dilute d-tartaric acid (TA) and of nonionic polysaccharides in water (c, = 0.05-0.07%) are in the same general t),- — ci orbit at 28°C. A sample of CMC (0.05 g) was dispersed in 80-mL water in 100-mL beakers to which TA was afterward added to different molarities TA supplied the H+ counterion intrinsic to an ionic polysaccharide and the nonintrusive tartrate ion. The solutions were transferred to 100-mL Erlenmeyer flasks and brought to volume with water prior to dilution viscometry. Judging from Fig. 7, a molar concentration of TA approximating 0.35 ensures an r sp/ci minimum in a dilute CMC dispersion (ci = 0.05-0.07%). 

Cesaro, A., and Villegas, M. (1996). Proton dissociation of ionic polysaccharides can the molecular weight be approximated by pH determinations Food Hydrocoil. 10 45-50. 

Reisenhofer, E., Cesaro, A., Delben, F., Manzini, G., and Paoletti, S. (1984). CoppeKH) binding by natural ionic polysaccharides. Part II. Polarographic data. Bioelectrochem. Bioenerg. 12 455-465 Chem. Abstr. 102 149687, 1985). 

Walter, R. H., and Jacon, S. A. (1994). Molecular weight approximations of ionic polysaccharides by pH determinations. Food Hydrocoll. 8 469-480. 

The ( >p pjj values needed for the computation of the Vp/Op values associated with the linear polyion, DxS, were obtained by interpolation of the ( )p versus a/b plots accessible for ionic polysaccharides (Fig. 12) where the b values were calculated with Eq. (16). Tlie log Kc and the log K, values determined for the commercially available DxS sample (Pharmacia), with a DS value of ca. 2, were also used at under various NaCl concentration levels. The Kf- values were determined in complex-ation studies facilitated by potentiometric measurements, whereas the Kj values due to Mattai and Kwak [46], were obtained by a dye method. In spite of the difference in valence of the counterions and the binding constants, the Vp/np values resolved for both systems are consistent with... 

In the preceding discussion of the relationship of the Donnan potential and the Donnan phase volume terms to the structural parameter of a linear polyion, a/b (A ), it has been shown that the elearostatic effect on the binding equilibria of ionic polysaccharides can be predicted quantitatively by use of the universal curves shown in Figs. 13 and 14. Also, by separating the overall binding equilibria into two processes, i.e., (1) the concentration of counterion in the polyion domain, territorial binding. 

In 1968, already back in Italy, Vittorio was called as full professor to the University of Trieste, where he founded the Macromolecular Chemistry Laboratory, leading a number of young scientists who still are active in the field of carbohydrate and polysaccharide chemistry. His main interest during this period was investigations on the polyelectrolytic properties of synthetic and natural polymers, including the very poorly studied ionic polysaccharides. 

These interactions are frequently ionic in character. The coulombic forces of interaction between macroions and lower molecular weight ionic species are central to the life processes of the cell. For example, intermolecular interactions of nucleic acids with proteins and small ions, of proteins with anionic lipids and surfactants and with the ionic substrates of enzyme catalyzed reactions, and of ionic polysaccharides with a variety of inorganic cations are all improtant natural processes. Intramolecular coulombic interactions are also important for determining the shape and stability of biopolymer structures, the biological function of which frequently depends intimately on the conformational features of the molecule. 

An important aim of physico-chemical studies on natural and synthetic ionic-polysaccharides is to help elucidate the correlations between chemical structure-conformational characteristics of such polymers and their equilibrium properties in solution. 

To our knowledge no calorimetric data of comparable accuracy on ionic polysaccharide solutions can be found in the literature, with the notable exception of the results recently reported by R. 

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