Sensitive competitive enzyme-linked immunoassay for quantitation of modified bases in DNA

A widely used configuration for competitive enzyme-linked immunosorbent assay (ELISA) of modified regions in polymeric DNA involves competition between a standardized quantity of antigen bound to the assay well and a variable quantity and/or quality of antigen in solution. These are competing for a limited standardized quantity of antibody in solution. The amount of antibody that binds to the immobilized antigen is measured and expressed as a percentage of the amount that binds in the absence of competing dissolved antigen. In this situation the amount of immobilized antigen is not generally known, but this is of no consequence, the essential feature being that the amount is highly uniform from well to well (see ref. 1 for a treatise on enzyme immunoassays).