Anti-B9 antibodies enable researchers to detect and measure the B9 antigen in biological samples. This target is a reported synonym of the NDUFA3 gene, which encodes NADH:ubiquinone oxidoreductase subunit A3. This protein is known to function in electron transport, among other biological roles. The human version of B9 has a canonical amino acid length of 84 residues and a protein mass of 9.3 kilodaltons. It is reported to be localized in the mitochondria of cells and widely expressed in many tissue types. B9 is a member of the Complex I NDUFA3 subunit protein family.