The Eagle Biosciences Apolipoprotein B ELISA Assay Kit employs the sandwhich enzyme immunoassay technique for the detection of Human Apolipoprotein B in human plasma, serum, and urine samples. Human Apolipoprotein B will bind to the capture antibody coated on the microtiter plate. After appropriate washing steps, anti-Human Apolipoprotein B primary antibody binds to the captured protein. Following a washing to remove unbound substances, secondary antibody conjugated to Horseradise Peroxidase (HRP) is added to each microplate well and incubated. After washing away any unbound antibody-enyme reagent, a substrate solution (TMB) is added to the wells and color develops in proportion to the amount of Apolipoprotein B bound in the initial step. The color development is stopped by the addition of acid and the intensity of the color is measured at a wavelength of 450nm ±2nm. The concentration of Apolipoprotein B in the sample is then determined by comparing the O.D. of samples to the standard curve. Sample Types: plasma, serum and urine. Range: 5 - 5000 ng/ml. Sensitivity: 1.5 ng/ml. Time: 4.5 hours ? Apolipoprotein B is the main apolipoprotein of chylomicrons and low density lipoproteins. It occurs in plasma as two main isoforms, apoB-48 and apoB-100: the former is synthesized exclusively in the gut and the latter in the liver. The intestinal and the hepatic forms of apoB are encoded by a single gene from a single, very long mRNA. The two isoforms share a common N-terminal sequence. The shorter apoB-48 protein is produced after RNA editing of the apoB-100 transcript at residue 2180 (CAA->UAA), resulting in the creation of a stop codon, and early translation termination. Mutations in this gene or its regulatory region cause hypobetalipoproteinemia, normotriglyceridemic hypobetalipoproteinemia, and hypercholesterolemia due to ligand-defective apoB, diseases affecting plasma cholesterol and apoB levels. Apolipoprotein B is a major protein constituent of chylomicrons (apo B-48), LDL (apo B-100) and VLDL (apo B-100). Apo B-100 functions as a recognition signal for the cellular binding and internalization of LDL particles by the apoB/E receptor.