Polycation salt

Polycation salts systems based on polyblend or polythienyl salts were prepared by synthetic routes (Scheme 3). 

Ionic conductivities of these polycation salts systems are shown in Figs. 23-25, which indicate higher ion conductivities than those of poly(ethylene oxide)-based polymers. The temperature dependence of the ionic conductivity for these polymers are also small in comparison with those of poly(ethylene oxide)-based polymers. Figure 26 summarizes the ion conductivities of these polycation-based SPE to compare their ion conductivities. 

We have studied stoichiometry of complex formation between DNA and PLL and found that the complexes formed in low-salt-buffer solutions are of a 1 1 charge ratio [92]. The same 1 1 stoichiometry was found experimentally for DNA complexed with other synthetic polycations of different nature in low-salt aqueous solutions [such as poly (diallyldimethylammonium chloride), poly(dimethyhmino)ethylene(dimethylimino)ethy-lene-l,4-dimethylphenylmethyl ene dichloride, andpoly(4-vinyl-A-methylpyridinium bromide)] [93]. 

It has been found that DTBP cross-linking substantially increased the salt stability of the complexes. The salt stabilization is reversed upon the addition of DTT, which cleaves the bifunctional reagent, indicating that it is not due to the conversion of the amines to amidines and is dependent upon the cross-linking. Similar results were achieved with other polycations, including poly(allylamine), and histone HI. 

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). 

Let us consider, for instance, the response mechanism of a polycation-selective galvanostatically controlled sensor. The polymeric membrane is in contact with a NaCl solution. The membrane of the sensor is formulated with a lipophilic salt, for instance, tetradodecylammonium dinonylnaphthalenesulfonate (TDDA-DNNS), which has a relatively high affinity to protamine. Even though protamine is presented in the sample, spontaneous extraction does not take place due to the high lipophilicity of TDDA-DNNS, thus the initial concentration of protamine or sodium cations in the membrane is close to zero. 

The majority of the aforementioned capsules were either not sufficiently mechanically stable or suffered from other surface or matrix related deficiencies. These deficiencies include poor morphology, such as capsule sphericity and surface smoothness, which result from an osmolar imbalance. Membranes are also often leaky (an internal polymer slowly diffuses out through the capsule wall) or shrink in either PBS or in culture media over a period of a few hours. Exceptionally, some capsules are observed to swell excessively and burst. Furthermore, some complex membranes, although stable in water, dissolve over several days upon a contact with culture media. This is true for pectin based capsules (pectin/calcium salt) and for alginate-chitosan membranes and maybe a consequence of the polycation substitution by electrolytes present in the media [10]. In order to improve the existing binary capsules several approaches, both traditional and novel, have been considered and tested herein. These are discussed in the following sections. 

Typically, a binary system was selected as the base component of the recipe and the addition of polyelectrolytes to either side (core or receiving bath) was tested to evaluate the change in the capsule properties. The 33 successful multicomponent membrane systems are presented in Table 1. The components of the core material side (21 different chemical compositions) are listed in the first column, while the receiving bath components (20 different chemical compositions) are listed in the second column. With the exception of xanthan and CMC, the first polymer listed on the core side are gelling polymers which form beads with the appropriate ionotropic cation (salt). CMC can also be gelled by ions (alum), although they are considered to be non-compatible for cellular applications. The cations were tested both sequentially, usually with ionotropic cation first, and simultaneously. Walled capsules with adequate mechanical properties were often obtained through the simultaneous application of two polycations. Such a... 

In recent years, it has been shown (Douzou and Maurel, 1976) that some proteins can behave as polyanions or polycations, and the stability of their solid state might be endangered at lower salt concentration due to repulsive forces between protein molecules. Much more important is the problem of enzyme activity in crystals suspended in cooled mixed solvents as a consequence of cosolvent- and temperature-induced changes in salt concentration and therefore in electrostatic potentials. 

The eight-atom systems provide a compelling illustration of the structural diversity of tellurium polycations. There are examples of (a) structural isomers of the monomeric dication Tcg, (b) a polymeric (Teg ) cation and (c) a tetracation Teg" . Unlike cyclo-Sg and -Seg , the Teg dication cannot be made by oxidising tellurium with MF5 (M = As or Sb) in liquid SO2. However, the reactions of (a) the tellurium subhalide Te3Cl2 with ReC at 200 °C and (b) tellurium with WCl6 at 180°C produce the salts Teg[MCl6] (w=l, M = Re ... 

Overall, the effects of polycations on the helix-coil transition of DNA are similar to those exhibited by the small cations both of them induce thermal stabilization of DNA duplex and decrease the cooperativity of the helix-coil transition In both cases the reasons for the stabilization effects are the screening of the negatively charged phosphate groups of the DNA, which reduces their electrostatic repulsion (Schildkraut, 1965). However, the effective concentration of a simple salt at which the same stabilization effect is achieved is ca. 103 times higher than the effective concentrations of a polycation. Consequently, polycations provide for a much more efficient screening of the DNA phosphate groups than the small cations. 

Once DNA has been condensed by a polycation, it is important for these complexes to retain a certain level of stability in salt solutions to allow sufficient time for cellular uptake of the particles. Izumrudov et al. (1999) studied the stability of a variety of polymers including polyvinylpyridines, linear poly amines, branched polyamines, polymethacrylates, and polyamides in salt solutions at a variety of pHs. They observed that polymers with predominantly primary amines produced the most stable polymer/DNA complexes followed by tertiary then quaternary amines, while higher molecular weight polymers resulted in more stable complexes for all amine types. Thus, it may be possible to specifically control complex stability by adjusting the relative amount of each amine type in the polymer. 

This chapter describes the structures and properties of supramolecular silver complexes with specific topologies such as cages, tubes, catenanes and polycate-nanes, rotaxanes and polyrotaxanes, and multidimensional frameworks, as synthesized by reactions of various silver salts with predesigned organic ligands. 

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