article chemical structure chemistry Molecular Structure 137 Models, Molecular 123 unclassified drug 52 metabolism 50 Crystallography, X-Ray 46 X ray crystallography 46 synthesis 44 animal 39 nuclear magnetic resonance spectroscopy 39 Humans 38 human 38 Animals 37 Ligands 37 Magnetic Resonance Spectroscopy 36 conformation 35 ligand 35 methodology 34 nonhuman 33 isolation and purification 32 controlled study 28 drug effect 27 Oxidation-Reduction 26 Quantum Theory 26 hydrogen bond 26 oxidation reduction reaction 26 quantum theory 26 Solvents 23