The DRG Amyloid ? 1-40 (human) ELISA (Abeta-40 ELISA) is an enzyme immunoassay for the quantitative in vitro measurement of human Amyloid ? peptide 1-40 in serum, plasma and CSF. The DRG Abeta-40 ELISA Kit is a solid phase enzyme-linked immunosorbent assay (ELISA) based on the sandwich principle. The microtiter wells are coated with a monoclonal [mouse] antibody directed towards a unique antigenic site on the Abeta-40 peptide. An aliquot of patient sample containing endogenous Abeta-40 peptide is incubated in the coated well with enzyme conjugate, which is a biotinylated anti-Abeta-40 antibody. After incubation the unbound conjugate is washed off. Finally, Enzyme Complex, which is streptavidin conjugated with horseradish peroxidase is added, and after incubation, unbound enzyme complex is washed off. The amount of bound peroxidase is proportional to the concentration of Abeta-40 peptide in the sample. Having added the substrate solution, the intensity of colour developed is proportional to the concentration of Abeta-40 in the patient sample.