Human Procollagen III N-Terminal Propeptide / PIIINP ELISA Kit (A75720) employs the sandwich enzyme immunoassay technique for the quantitative measurement of human Procollagen III N-Terminal Propeptide / PIIINP in serum, plasma, tissue homogenates, and other biological fluids. An antibody specific for Procollagen III N-Terminal Propeptide / PIIINP has been pre-coated onto a 96-well microtiter plate. The standards and test samples are added into the wells and the Procollagen III N-Terminal Propeptide / PIIINP present in each sample is bound to the wells by the immobilized antibody. Following incubation, the wells are washed and then incubated with Biotinylated Anti-Procollagen III N-Terminal Propeptide / PIIINP Antibody, which binds the captured Procollagen III N-Terminal Propeptide / PIIINP present in each well. Following incubation, unbound biotinylated detection antibody is removed by washing, and an HRP-Streptavidin conjugate is added to the wells and the microtiter plate is incubated. Following incubation and washing, TMB substrate solution is then used to visualize the HRP enzymatic reaction by catalysis to produce a blue-coloured product that changes to yellow after addition of acidic stop solution. The density of yellow is proportional to the amount of Procollagen III N-Terminal Propeptide / PIIINP captured in each well. The concentration of Procollagen III N-Terminal Propeptide / PIIINP can then be calculated by reading the O.D. absorbance at 450nm in a microplate reader and referring to the standard curve.