Apolipoprotein A2 (APOA2) is a major protein component of serum HDL. It is produced by the liver and is involved in cholesteryl ester formation and cholesterol transport from tissues to the liver. Polymorphisms of APOA2 are associated with disorders of cholesterol and fatty acid metabolism. APOA2 can form disulfide-linked 17 kDa homodimers and heterodimers with other apolipoproteins. Mature human APOA2 shares 96% aa sequence identity with chimpanzee APOA2 and 48% - 66% aa sequence identity with bovine, equine, mouse and rat APOA2. A functional ELISA assay was conducted to detect the interaction of recombinant human APOA2 and recombinant rat APOC1. Briefly, APOC1 was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to APOA2-coated (1ug/ml, 100 ul/well) microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-APOC1 pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody for 1h at 37℃, wells were aspirated and washed 5 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37℃. Finally, add 50 µL stop solution to the wells and read at 450/630nm immediately. The binding activity of recombinant human APOA2 and recombinant rat APOC1 was shown in Figure 1, the concentration of APOC1 that produces 50% optimal binding response is found to be approximately 87.2 ng/mL.