K+/Na+ selectivity by experiment and calculation
| Method | Solvent | ΔΔG (kcal/mol) | Selective for |
| Formamidea | −0.9 | Na+ | |
| Experiment | Formamidebc | −0.7 | Na+ |
| NMAbd | −1.1 | Na+ | |
| Formamidec (CHARMM27) | 0.9 | K+ | |
| Formamidec (OPLS-AA) | 1.3 | K+ | |
| Pairwise Additive | NMAe (CHARMM22) | 1.6 | K+ |
| NMAcd (CHARMM27) | 2.8 | K+ | |
| NMAcd (CHARMM27/NBFIX) | 4.7 | K+ | |
| Formamidec (AMOEBA) | −1.3 | Na+ | |
| Polarizable | Formamidef (QM/MM) | −2.2 | Na+ |
| NMAd (Drude) | −0.3 | Na+ |
| Method | Solvent | ΔΔG (kcal/mol) | Selective for |
| Formamidea | −0.9 | Na+ | |
| Experiment | Formamidebc | −0.7 | Na+ |
| NMAbd | −1.1 | Na+ | |
| Formamidec (CHARMM27) | 0.9 | K+ | |
| Formamidec (OPLS-AA) | 1.3 | K+ | |
| Pairwise Additive | NMAe (CHARMM22) | 1.6 | K+ |
| NMAcd (CHARMM27) | 2.8 | K+ | |
| NMAcd (CHARMM27/NBFIX) | 4.7 | K+ | |
| Formamidec (AMOEBA) | −1.3 | Na+ | |
| Polarizable | Formamidef (QM/MM) | −2.2 | Na+ |
| NMAd (Drude) | −0.3 | Na+ |
K+/Na+ selectivity of bulk liquid formamide and NMA as determined by experimental work, pairwise-additive (nonpolarizable) force field calculations, polarizable force field (AMOEBA and Drude) calculations, and QM/MM (hybrid quantum mechanical and molecular mechanical) calculations. Note that the pairwise-additive force field calculations display positive (K+) selectivity, whereas all other determinations display negative (Na+) selectivity.
Marcus, 1983.
Cox and Parker, 1973, and Schmid et al., 2000.
Grossfield et al., 2003.
Yu et al., 2010a.
Noskov et al., 2004.
Varma and Rempe, 2008.