Poses of docked compound 21 in to the DNA binding region of NF-kappaB p50. A. monomer and B. homodimer (chain A, shown in grey). The inhibitory activity of 21 may be due to its ability to form a stable complex with the active conformation of the dimer and/or blocking the interaction of DNA with the monomer filling the protein binding site. The DNA was obtained from the crystal structure of the homodimer NF-kappaB (pdb code:1NFK). The surface of the protein is represented in wire frame, the ligand and DNA are highlighted in VDW and stick representation respectively.