Collagen Type I Alpha 2 (COL1a2) ?is a major component of collagen type I found in skin, bone, muscle, tendons, ligaments and other connective tissues.The COL1a2 protein is essential for the assembly, secretion, and stability of collagen fibers, which are vital for tissue development and repair.Mutations in COL1A2 are associated with a variety of genetic disorders, such as osteogenesis imperfecta (dysplasia of the bones) and cutis laxa. These diseases are often accompanied by weak bones and loss of skin elasticity. Besides, Fibrillin 1 (FBN1) has been identified as an interactor of COL1a2, thus a functional binding ELISA assay was conducted to detect the interaction of recombinant rat COL1a2 and recombinant human FBN1. Briefly, COL1a2 was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to FBN1-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-COL1a2 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 450/630 nm immediately. The binding activity of recombinant rat COL1a2 and recombinant human FBN1 was shown in Figure 1, the EC50?for this effect is 2.53 ug/mL.