TOWARDS NEW FORMULATIONS FOR POLYACRYLAMIDE MATRICES, AS INVESTIGATED BY CAPILLARY ZONE ELECTROPHORESIS

Several new aspects of polyacrylamide gel polymerization were investigated. First, a series of mono- and disubstituted acrylamide monomers were evaluated as potential candidates of a novel class of polyacrylamide matrices, exhibiting high hydrophilicity, high resistance to hydrolysis and larger pore size than conventional polyacrylamide gels. A series of cross-linkers were also assessed and their contributions to the gel stability and hydrophilicity evaluated. A novel method of photopolymerization is described, consisting of photoinitiating the reaction with methylene blue in the presence of a redox couple (sodium toluenesulphinate and diphenyliodonium chloride). The photobleaching curve gives direct information on the conversion efficiency of monomers into the growing polymer. In addition, photopolymerized gels have a better elastic modulus than peroxodisulphate-initiated gels. A unique correlation is described between the Phantom modulus and protein mobilities as a function of the percentage of cross-linker: a maximum of Phantom modulus corresponds to a minimum of mobility and both of these values occur at 5% of cross-linker. A novel method is described for producing extremely large-pore gels: polymerization in presence of a preformed, hydrophilic polymer (typically PEG 20 000 or PEG 10 000). In the presence of the latter polymers (up to 2-2.5%), ''lateral-chain aggregation'' occurs, with an extremely large expansion of pore size. For example, while a 5%T, 4%C gel typically has an average pore diameter of 5-6 nm, the same gel, in the presence of a ''laterally aggregating agent'' exhibits an average pore size of 500 nm.