PROTEIN ELECTROPHORESIS IN POLYACRYLAMIDE GELS WITH TEMPLATED PORES

An approach is described for the synthesis of nanostructured hydrogels with defined size channels or pores for separations of biological mac romolecules. Polyacrylamide gels (15-20% acrylamide) were cast in the presence of high concentrations (5%-28%) of hydrophilic, macromolecula r cosolutes either semirigid, rod-like polyelectrolytes (short fragmen ts of DNA or xanthan) or spherical micelles of sodium dodecyl sulfate (SDS). Polyanionic cosolutes were then removed by a combination of dif fusion and electrophoresis. These processes are expected to yield gels with 'templated' channels having dimensions near those of the double helical polymers (diameters approximate to 2-3 nm, lengths of 50-200 n m) or pores near the size of the spherical SDS micelles (approximate t o 4-5 nm). This hypothesis was tested by comparing the relative electr ophoretic mobilities of proteins (3400 to 43 000 Da) complexed with SD S on templated and conventional gels. Differences in electrophoretic m obilities were observed between all templated gels and control normal gels, demonstrating that the templating process altered the polyacryla mide network. No evidence was found for phase separation of cosolutes from the polyacrylamide network during polymerization. Templated pores are expected to enhance the mobilities of molecules in a particular s ize range relative to smaller and larger molecules. Gels templated wit h DNA or xanthan (8-10% final concentration) exhibited little size sel ectivity, but selectivity was observed for gels templated with SDS (17 -20% final concentration). The degree of selectivity of gels templated with SDS varied with polyacrylamide concentration in a manner consist ent with the creation of templated pores approximately the size of SDS micelles and larger than the average pore size in a surrounding polya crylamide network.