An enzyme-linked immunosorbent assay for zein and other proteins using unconventional solvents for antigen adsorption

An enzyme-linked immunosorbent assay (ELISA) performed in polystyrene microtiter plates that can detect and quantitate the maize prolamin zein is described. The assay yields positive reactions with as little as 1 ng of antigen and uses solvents not ordinarily employed in ELISA methods. A systematic investigation of zein adsorption to polystyrene in various solvents supports the hypothesis that antigen binding occurs through nonpolar interactions. The method was also used to determine structural relationships among three zein polypeptides differing in size and charge. Additional experiments indicate that a number of soluble proteins are absorbed to polystyrene in the denaturing agent urea and retain immunological reactivity. The retention of antigen reactivity after solubilization in 6-8 M urea suggests that ELISA methods may be applicable to other proteins which are insoluble, or rendered insoluble, in aqueous buffers.