Models of three glutathion S-transferase (GST) isozymes with bound Meisenheimer complex of compound 1, 2, and 4 (PABA/NO). The GST active sites are illustrated as non-transparent surfaces, except for a transparent surface in panels c and g to show the unfavorable interaction between the ligand and the protein (indicated with red arrows), and the ligands as stick models in atomic color scheme (carbon in green, nitrogen in blue, oxygen in red, and sulfur in orange). (Ji, Pal, Kalathur, Hu, Gu, Saavedra, Buzard, Srinivasan, Keefer, and Singh. Drug Design, Development and Therapy 2008; 2:123-130. Full Text).