R-Spondin 1 (RSPO1) BioAssay? ELISA Kit (Human) is a Sandwich enzyme immunoassay. The microtiter plate provided in this kit has been pre-coated with an antibody specific to R-Spondin 1 (RSPO1). Standards or samples are then added to the appropriate microtiter plate wells with a biotin-conjugated antibody specific to R-Spondin 1 (RSPO1). 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 R-Spondin 1 (RSPO1), 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 450nm±10nm. The concentration of R-Spondin 1 (RSPO1) in the samples is then determined by comparing the O.D. of the samples to the standard curve. Detection Range: 15.625-1000pg/ml Sensitivity: <5.8pg/ml