Positive ions article 18 priority journal 7 unclassified drug 7 Animals 6 Density functional theory 6 Kinetics 6 Negative ions 6 cation 6 Calcium 5 Electronic structure 5 Enzymes 5 Hydrogen bonds 5 Oxygen 5 chemical structure 5 chemistry 5 controlled study 5 Charge transfer 4 Electron energy levels 4 Ligands 4 Lithium 4 Mass spectrometers 4 Mass spectrometry 4 Organic compounds 4 Quantum Theory 4 Rubidium 4 Sodium 4 Swine 4 adenosine triphosphatase (potassium sodium) 4 nonhuman 4