Purity ≥95% as determined by SDS-PAGE and HPLC. Inhibitor of bone morphogenetic proteins (BMP) signaling which is required for growth and patterning of the neural tube and somite. Essential for cartilage morphogenesis and joint formation. Inhibits chondrocyte differentiation through its interaction with GDF5 (PubMed:21976273). (ECO:0000269|PubMed:12478285, ECO:0000269|PubMed:21976273). Biological Activity: Fully biologically active when compared to standard. The ED50 as determined by inhibiting BMP-4- induced alkaline phosphatase production of murine ATDC5 cells is less than 3.0ng/ml, corresponding to a specific activity of 3.3x10e5 IU/mg in the presence of 5ng/ml rHuBMP-4.