Acetylcholine (top) and nicotine (bottom) docked to the agonist binding site of human nAChR alpha4-beta2. Left: the ligands would form a polar interaction with the delocalized electron of Trp182, and with a water molecule (green) coordinated by Trp182, Leu146 and Ser133. Right: space filling representation shows how the ligands occupy the binding pocket (yellow). Color coding is magenta: ligand, gold: subunit alpha4, cyan: subunit beta2, blue: nitrogen, red: oxygen, yellow: sulfur. Most hydrogen atoms (gray) are not shown for clarity.