Polyvalent cations, binding

Torchilin, V.P. Klibanov, A.L. Nossiff, N.D. Slinkin, M.A. Strauss, H.W. Haber, E. Smirnov, V.N. Khaw, B.A. Monoclonal antibody modification with chelate-linked high-molecular-weight polymers major increases in polyvalent cation binding without loss of antigen binding. Hybridoma 1987, 6, 229-240. 

With strong cation-exchangers (e.g. with SO3H groups), the usual sequence is that polyvalent ions bind more firmly than mono- or di- valent ones, a typical series being as follows ... 

The tetracyclines are well known for their ability to form complexes with polyvalent cations. This property changes their solubility characteristics in the mobile solvents and often results in troublesome streaking. To overcome this difficulty, Selzer and Wright used paper dipped in Mcllvaine s buffer (pH 3.5) which contains citrate ions capable of binding the metallic ions. The chromatograms were developed with a mixture of nitromethane, chloroform, and pyridine (20 10 3) on paper still damp from the treatment with the buffer solution. 

Traditionally, polyvalent cation-phytate complexes have been considered uniformly insoluble, and this dogma has been the basis of most methods for the determination of phytate (31). In 1976, however, soluble monoferric phytate was isolated (32), and most recently, Cai- and Ca2 phytate were also found to be soluble (27). Figure 2 shows a Scatchard plot of Ca2+ binding to phytate at pH 4.8. At a ratio of 2.2 to 2.4 the complex precipitates. This ratio is independent of the phytate concentration over a 100-... 

Humus can form stable complexes such as chelates with polyvalent cations. SOM is capable of strong polydentate binding to transition metals in a chelate [17,19,45, 65-67]. The complexation of metal ions by SOM is extremely important in affecting the retention and mobility of metal contaminants in solid phases and waters [45]. Several different types of SOM/humus-metal reactions can occur (Fig. 11), and include reactions between DOC-metal ions, complexation reactions between SOM-metal ions, and bottom sediments-metal ions. The functional groups of SOM (Fig. 10) have different affinities for metal ions as shown below ... 

Ion bridging is a specific type of Coulombic interaction involving the simultaneous binding of polyvalent cations (e.g., Ca, Fe, Cu ) to two different anionic functional groups on biopolymer molecules. This type of ionic interaction is commonly involved in associative self-assembly of biopolymers. As a consequence it is also an important contributory factor in the flocculation (via bridging or depletion) of colloidal particles or emulsion droplets in aqueous media containing adsorbed or non-adsorbed biopolymers (Dickinson and McClements, 1995). 

In a continuation of studies with pAPhEDTA, it has been shown that monoclonal antibodies raised against antigens bearing a chelated polyvalent cation exhibit a high specificity for the trivalent metal ion. Replacement of indium(III), for instance, by scandium(III) or gallium(III) can decrease the antibody-binding constant by more than three orders of magnitude223. ... 

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-... 

The above interpretation appears to explain many membrane fusion events observed for model membrane systems the divalent or polyvalent cation-induced membrane fusion is directly related to the surface energy increase (to become more hydrophobic) of the membrane caused by binding of these ions to the membranes. The increased temperature or osmotic pressure-... 

Zn conclusion, one can say that the iduronic acid of heparin is a prefarential complexing site for polyvalent cations as shown by a set of different MMR data. This result is in agreement with the recent fit ing of Lasslo (17) on how heparin binds sodium. 

Several naturally occurring anionic polysaccharides exist alginic acid, pectin, carrageenans, xanthan gum, hyaluronic acidic, gum exudates (gum arabic, karaya, traganth, etc.). Cross-linking sites that occur when a polyvalent cation (e.g. Ca +) causes interpolysaccharide binding are called "junction zones . 

Fulvic acids are the primary type of humic substances that bind metal ions since they contain many oxygen-containing functional groups. Many of the low-molecular-mass ligands, however, can form more stable complexes with polyvalent cations than do fulvic acids. 

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