Distribution of cytochrome c in polyacrylate microgels

Abstract

The uptake of cytochrome c from aqueous solution (pH = 7, ionic strength 40 mM) into weakly cross-linked sodium polyacrylate microgels is investigated by means of micromanipulator-assisted light microscopy and laser scanning confocal microscopy. It is shown that the protein is distributed uniformly in the gels at equilibrium. The kinetics of the interaction is investigated by means of time-resolved deswelling curves, and by observations of the diffusion fronts of fluorescently labeled cytochrome c in single gel particles. The time to reach the deswollen equilibrium state of the gels is short, in general, and decreases rapidly with increasing protein concentration in the solution, indicative of a rapid diffusive transport inside the microgels. The results are compared with results for lysozyme binding with the same type of network, and with results for macrogels in the literature. The importance of net attractive protein–protein forces for the mechanism of binding is highlighted.