Amyloid beta (A4) Precursor Protein (APP) ELISA Kit: The microtiter plate provided in this kit has been pre-coated with an antibody specific to Ab1-40. Standards or samples are then added to the appropriate microtiter plate wells with a biotin-conjugated antibody specific to Ab1-40. Next, Avidin conjugated to Horseradish Peroxidase (HRP) is added to each microplate well and incubated. After TMB substrate solution is added, only those wells that contain Ab1-40, biotin-conjugated antibody and enzyme-conjugated Avidin will exhibit a change in color. The enzyme-substrate reaction is terminated by the addition of sulphuric acid solution and the color change is measured spectrophotometrically at a wavelength of 450 nm