Anion polyanions

Coles and Gross (5, 6) have found that some of the penicillinase of Staphylococcus aureus is bound ionically to the surface of the cell wall and can be liberated by low concentrations of anions. Polyanions that do not penetrate the cell wall and tricarboxylic acids were particularly effective as release agents Weimberg and Orton (16) had found earlier that acid phosphatase could be released from the cell surface of Saccharo-myces mellis by chloride ions in combination with 2-mercaptoethanol and concluded that this enzyme is held on the cell surface by a combination of electrostatic forces and disulfide bonds. Likewise, polygalacturonase is released from the surface of spores of Geotrichum candidum with polyanions and 2-mercaptoethanol (2). 

CMC hydrates rapidly and forms clear solutions. Viscosity buUding is the single most important property of CMC. DUute solutions of CMC exhibit stable viscosity because each polymer chain is hydrated, extended, and independent. The sodium carboxylate groups are highly hydrated, and the ceUulose molecule itself is hydrated. The ceUulose molecule is linear, and conversion of it into a polyanion (polycarboxylate) tends to keep it in an extended form by reason of coulombic repulsion. This same coulombic repulsion between the carboxylate anions prevents aggregation of the polymer chains. Solutions of CMC are either pseudoplastic or thixotropic, depending on the type. 

Anions with 8, and probably 16-18, Mo atoms also appear to be formed, before increasing acidity suffices to precipitate the hydrous oxide. It is clear from the above equation that the condensation of M0O4 polyhedra to produce these large polyanions requires large quantities of strong acid as the supemumary oxygen atoms are removed in the form of water molecules. Careful... 

Since multiple electrical and optical functionality must be combined in the fabrication of an OLED, many workers have turned to the techniques of molecular self-assembly in order to optimize the microstructure of the materials used. In turn, such approaches necessitate the incorporation of additional chemical functionality into the molecules. For example, the successive dipping of a substrate into solutions of polyanion and polycation leads to the deposition of poly-ionic bilayers [59, 60]. Since the precursor form of PPV is cationic, this is a very appealing way to tailor its properties. Anionic polymers that have been studied include sulfonatcd polystyrene [59] and sulfonatcd polyanilinc 159, 60]. Thermal conversion of the precursor PPV then results in an electroluminescent blended polymer film. 

The tendency of the halogens to form chain-like polyanions that are stabilized by delocalization of the negative charge [15,34] is a basic chemical principle. Donor-acceptor interactions between Lewis-acidic Br2 and halide anions, but also with polyhalides acting as Lewis bases, give rise to the formation of a variety of homo and heteroatomic adducts. The maximum number of atoms in these chains increases with the atomic weights... 

Ladenheim and Morawetz [23] also showed that the reactivity of the carboxylate units in partially ionized poly(methacrylic acid) (PMA) toward BrCH2COO in the bromine displacement reaction was greatly diminished, while the reaction proceeded at an appreciable rate with uncharged p-bromoacetamide [23]. This inhibition of the reaction of the polyanion with a small anionic reagent can be attributed to the electrostatic repulsion between the polymer and the reagent. 

In most cases the microspheres were insoluble. The polysaccharides might be partially cross-linked via amido groups formed by the carboxyl groups of the polyanion and the restored free amino group of chitosan. The susceptibility to enzymatic hydrolysis by lysozyme was poor, mainly because lysozyme, a strongly cationic protein, can be inactivated by anionic polysaccharides [207]. 

In equilibrium dialysis of a solution of a polyanion (valence Zp negative) with molar concentration Cp against a solution of imi-imivalent electrolyte CA (C = cation, A = anion) with molar concentration Cqa it was shown that the requirement for equal chemical potentials of the salt in the polyanion (a) and diffusate ()) phases results in the following relation... 

Comparison of the concentrations of either the cation or the anion in the two phases thus has potential for evaluating the polyanion valence provided that estimates of the mean ion activity coefficient (y ) are available. Furthermore, as realized by Svensson [165], expression of the Donnan distribution of small ions in this manner has two advantages in that (i) Eq. 31 applies to each type of small ion in situations where the supporting electrolyte is not restricted to single cationic and anionic species and (ii) multivalence of a small ion is also accommodated. 

Solutions of polyelectrolytes contain polyions and the free (individual) counterions. The dissociation of a polyacid or its salt yields polyanions, and that of a polybase or its salt yields polycations, in addition to the simple counterions. The polyampholytes are amphoteric their dissociation yields polyions that have anionic and cationic functions in the same ion and often are called zwitterions (as in the case of amino acids having HjN and COO groups in the same molecule). Such an amphoter will behave as a base toward a stronger acid and as an acid toward a stronger base its solution properties (particularly its effective charge) will be pH dependent, and an isoelectric point (pH value) exists where anionic and cationic dissociation is balanced so that the polyion s charges add up to zero net charge (and solubility is minimal). 

Previously, Osaka and coworkers [29-31] employed ion-transfer voltammetry to determine the standard ion-transfer potentials (Aq 4> ) of heteropoly- and isopolyoxome-talate anions (in short, polyanions) at the nitrobenzene (NB)/W and 1,2-dichloroethane (1,2-DCE)/W interfaces is directly related to the transfer energy by... 

The coefficients Co, nnd C2 (denoted as mq, ai, and aj in Ref. 33) are influenced by various molecular properties of the solvent and an ion, including their electron-donating or accepting abilities. Hence, these coefficients are specific to the ion. Nevertheless, they may be considered as common to a family of ions such as the polyanions whose surface atoms, directly interacting with solvents, are oxygens. This is the case for hydrated cations or anions whose surfaces are composed of some water molecules that interact with outer water molecules in the W phase or with organic solvents in the O phase. 

In the present analyses [49], 34 ions are classified into five groups (1) hydrated cations, (2) nonhydrated cations, (3) hydrated anions, (4) nonhydrated anions, and (5) polyanions. Here, the term hydrated or nonhydrated means that the ion is associated with some water molecules in the O phase or not, respectively. 

The numbers ( ) of coextracted water molecules shown in Table 3 are from Table 2 [46]. In the case of -Pr4N, metal complex cations, larger anions of r > 0.23 nm, and polyanions, it is assumed that n = 0. Although the n value of [Fe(phen)3] or CIO4 was reported to be as small as 0.3 or 0.2 [46], these ions have been classified as nonhydrated (i.e., = 0) so that comparatively better results may be obtained. 

FIG. 11 Plots of AGtr z-d p)/ Aitr ) against E for nonhydrated cations (A) and anions (A) and polyanions ( ). Solid lines show the regression curves [Eqs. (49), (50), and (51)]. (From Ref. 49. Copyright 1998 American Chemical Society.)... 

These results indicate that the surface-anchored DNA blocks the electrochemical reaction of [Fe(CN)6]" with the underlying Au electrode, due to the electrostatic repulsion between the polyanionic DNA and the anionic redox couple ions. 

Table 13.1 Examples of polyanionic compounds which have integral valence electron concentrations per anion atom...

Fig. 1.15 A schematic representation of a polyacid solution including polyanions , anions of an added low molecular electrolyte O and positive counterions ...

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