Anti-p21 antibodies enable researchers to detect and measure the p21 antigen in biological samples. This target is a reported synonym of the NSG1 gene, which encodes neuronal vesicle trafficking associated 1. This protein is known to function in the apoptotic pathway, among other biological roles. The human version of p21 has a canonical amino acid length of 185 residues and a protein mass of 20.9 kilodaltons, although 2 isoforms have been identified. p21 is a member of the NSG protein family.