Description(s):
Pappalysin-1 (PAPPA) is a protein secreted by the embryo and the placenta during pregnancy. PAPPA is a metalloproteinase which cleaves insulin-like growth factor binding proteins. Low plasma levels of PAPPA are commonly observed in pregnancies with aneuploid fetuses. Because of this, PAPPA can be used as a biomarker for conditions such as Down syndrome.
Principle
The wells of the plate are coated with capture antibody specific to PAPPA. In this assay, the test sample initially reacts with the solid phase capture antibody, resulting in PAPPA being bound to the well. The wells are then washed to remove unbound proteins, and biotin-linked antibodies are added to bind to the immobilized PAPPA. After washing away the unbound antibodies, Streptavidin-HRP conjugate is added to form a complex with the antibody-bound PAPPA. After incubation, the wells are washed to remove unbound Streptavidin-HRP conjugate. TMB substrate is then added and forms a blue color when the HRP-linked antibodies are detected. The reaction is then terminated with Stop Solution, which changes the color from blue to yellow. The PAPPA concentration in each well is directly proportional to its color intensity and can be quantified by measuring its optical density at 450 nm (OD450) in a microplate reader.
