Biotin-modified submicron latex particles for affinity precipitation of avidin

The negatively-charged latex particles (latex-COO-) is more effective in binding lysozyme via electrostatic interactions than avidin. The zeta potential data suggest that a portion of the carboxyl groups can be trapped inside the network of large flocs formed during the precipitation process. Thus the entrapped binding sites are no longer available for protein as the precipitation process proceeds. This action can reduce the maximum amount of protein adsorbed on the particle surface. The selectivity of the precipitation process using latex-COO- as the polymeric support is in favor of lysozyme for the mixture of avidin and lysozyme. Latex-COO- can be used to concentrate the target protein avidin from a crude extract. The biotin-modified latex (latex-biotin) can then be used in a subsequent step to purify avidin via affinity interactions from an intermediate product containing avidin and lysozyme. The selectivity of the affinity precipitation process using latex-biotin as the support is satisfactory with respect to the protein mixture containing avidin and lysozyme.