Polyanion-polycation complexes

The polyanion-polycation complex (symplex) formation process is a phenomenon that had long been known on an empirical base from the mutual precipitation of proteins [150]. The internal structure and the properties of the resulting complexes are strongly influenced by the nature of the polymeric components and the system conditions. The polymer parameters include the molar mass, the... 

Laugel N, Betscha C, Winterhalter M et al (2006) Relationship between the growth regime of polyelectrolyte multilayers and the polyanion/polycation complexation enthalpy. J Phys ChemB 110 19443-19449... 

K5tz, J. Koepke, H. Schmidt-Naake, G. Zarras, P. Vogl, O. Polyanion-polycation complex formation as a function of the functional-groups. Polymer 1996, 57 (13), 2775-2781. 

In former investigations by using a combined titration technique [25] we could already show that the turbidimetric endpoint of the polyanion-polycation complex formation in the absence of kaolin correlates quite well with the one in the presence of kaolin. This agreement means that polyanion-polycation interactions are dominant in this system and the complexes with kaolin were formed due to an interparticle bridging through the polyelectrolyte complexes formed on kaolin. 

Synthesis and characterization of some insoluble polyanion—polycation complexes. J Polym Sci Part A Polym Chem 1996 34(17) 3485-3494. 

Cellulose sulfate, in particular C6 sulfates, can be used for preparing polyanion-polycation complexes for pervaporation membranes (43 5). 

Michaels AS, Falkenstein GL, Schneidta- NS (1965) Dielectric properties of polyanion-polycation complexes. J Phys Chem 69 1456-1465... 

Polyanion-polycation-complexes are known for a long time on an empirical basis from the mutual precipitation of proteins. Already at the end of the previous century Kossel [1] recognized the electrostatic interaction between the oppositely charged polyions as the driving force for precipitation. Willstaetter [2] also introduced the term symplexes for polyelectrolyte complexes. 

On the other hand polyanions modulate the behavior of polycations through formation of polyanion-polycation complexes. For instance, heparin reversed the anatomo-pathological abnormalities induced by poly(L-lysine) (PLL). In contrast, it had little effect on the in vivo toxicity of a polybase of the partially quatemized poly(tertiary amine)-type, namely poly[thio-l diethyl-aminomethyl)- -ethylene], (Q-P(TDAE)x with x = percentage of quatemized subunits). It was thus observed that a same poly anion, namely heparin, can alleviate harmful effects of one polycation and have little effect on the toxicity of another one. The latter author even noticed that a polyanion-polycation complex can unexpectedly be more toxic than the isolated polycation in the case of a poly(ethyleneglycol)-block-poly(aspartic acid) and Q-P(TDAE)x. 

Based on the present understanding of polyanion-polycation complexes and given the complexity of the composition of plasma in proteins with various polyelectrolyte properties, one can consider that a synthetic polycation faces a great number of competing polyanionic systems, including RBC, when introduced in whole blood. The identification of the... 

Table 5 summarizes the type of complex produced for each polyanion-polycation pair investigated. There are relatively few systems which yielded soluble complexes (13.6%) with the majority of polyanion-polycation reactions yielding either precipitates (43.7%) or weak membranes (30.7%). Indeed, as one scans across rows of polycations or down columns of polyanions, many of the naturally occurring or synthetic species predominantly form precipitates. This is, perhaps, due to the high content of ionic groups (one per repeat unit) charac-... 

The behaviour of ternary systems consisting of two polymers and a solvent depends largely on the nature of interactions between components (1-4). Two types of limiting behaviour can be observed. The first one occurs in non-polar systems, where polymer-polymer interactions are very low. In such systems a liquid-liquid phase separation is usually observed each liquid phase contains almost the total quantity of one polymer species. The second type of behaviour often occurs in aqueous polymer solutions. The polar or ionic water-soluble polymers can interact to form macromolecular aggregates, occasionally insoluble, called "polymer complexes". Examples are polyanion-polycation couples stabilized through electrostatic interactions, or polyacid-polybase couples stabilized through hydrogen bonds. 

Previous synthesis of this complex at twice the present scale gave a yield of 70% (see refs. 1 and 2a), the present synthesis gives a 52% yield, and syntheses done at one-third of the present scale are less satisfactory, giving overall yields of approximately 30°/. Clearly, the observed yields are significantly concentration-dependent (as perhaps would be expected given the polyanion-polycation nature of the complex), and it appears that yields > 70% are possible from syntheses done at larger scale. 

All these results clearly indicate that the BT-HAase activity towards HA can be either enhance or suppress by formation of electrostatic complexes. The BT-HAase activity can be enhance by polycations, which in vivo are mainly proteins, to the condition that (i) they are able, by forming electrostatic complexes with HA, to avoid, or at least to limit, the formation of electrostatic complexes between HA and BT-HAase and, (ii) the ratio of the polycation over HA quantities in the HA-polycation complexes allows enough HA P(l,4) bonds to remain accessible to BT-HAase. Suppression of the BT-HAase activity may result from the formation of two types of electrostatic complexes (i) HA-polycation complexes in which the accessibility of BT-HAase to the HA P(l,4) bonds is hindered because of a too high value of the ratio of the polycation over HA quantities in the complexes and, (ii) polyanion-BT-HAase complexes in which BT-HAase is catalytically inactive. In our study, the only one polyanion was HA and we showed that it is able to form electrostatic complexes with BT-HAase in which BT-HAase is catalytically inactive. Nevertheless, many polyanions, including GAG other than HA (heparin, heparan sulfate, dermatan sulfate), HA derivatives (0-sulfonated HA) and synthetic polyanions (poly(styrene-4-sulfonate)) are known to inhibit HAase (Aronson and Davidson, 1967 Girish and Kemparaju, 2005 Isoyama et al., 2006 Mathews and Dorfman, 1955 Toida et al., 1999). In the case of heparin, Maksimenko et al. (2001) demonstrated that the inhibition results from the formation of electrostatic heparin-HAase complexes. 

Since the complexation between proteins and polyelectrolytes is caused by Coulomb interaction, it has been evident that increasing pH promotes the formation of protein-polycation complexes, and decreasing pH enhances complexation of proteins and polyanions [19]. From the fluorescence study of papain-PVS complex, Cha et al. [29] found the the emission shift for the complex strongly depends on the pH, as shown in Fig. 15.13. 

Danielsen, S., Maurstad, G., Stokke, B.T. DNA-polycation complexation and polyplex stability in the presence of competing polyanions. Biopolymers 77, 86-97 (2004). doiilO. 1002/bip.20170... 

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