ERROR opening https://cactus.nci.nih.gov/chemical/structure/NH4%20.NH4%20.O-2.O-2.O-2.O-2.O-2.O-2.O-2.U.U/file?format=sdf&get3d=True  -- NH4%20.NH4%20.O-2.O-2.O-2.O-2.O-2.O-2.O-2.U.U could not be loaded.