Table I.

K+/Na+ selectivity by experiment and calculation

Method Solvent ΔΔG (kcal/mol) Selective for 
Experiment Formamidea −0.9 Na+ 
Formamidebc −0.7 Na+ 
NMAbd −1.1 Na+ 
Pairwise Additive Formamidec 0.9 K+ 
(CHARMM27)   
Formamidec 1.3 K+ 
(OPLS-AA)   
NMAe 1.6 K+ 
(CHARMM22/NBFIX)   
NMAdg 0.7* K+ 
(CHARMM27)   
NMAdg 2.6* K+ 
(CHAEMM27/NBFIX)   
Polarizable Formamidec −1.3 Na+ 
(AMOEBA)   
Formamidef −2.2 Na+ 
(QM/MM)   
NMAd −0.3 Na+ 
(Drude)   
Method Solvent ΔΔG (kcal/mol) Selective for 
Experiment Formamidea −0.9 Na+ 
Formamidebc −0.7 Na+ 
NMAbd −1.1 Na+ 
Pairwise Additive Formamidec 0.9 K+ 
(CHARMM27)   
Formamidec 1.3 K+ 
(OPLS-AA)   
NMAe 1.6 K+ 
(CHARMM22/NBFIX)   
NMAdg 0.7* K+ 
(CHARMM27)   
NMAdg 2.6* K+ 
(CHAEMM27/NBFIX)   
Polarizable Formamidec −1.3 Na+ 
(AMOEBA)   
Formamidef −2.2 Na+ 
(QM/MM)   
NMAd −0.3 Na+ 
(Drude)   

K+/Na+ selectivity of bulk liquid formamide and NMA as determined by experimental work, pairwise-additive (nonpolarizable) force field calculation, 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.

a

Marcus, 1983.

b

Cox and Parker, 1973, and Schmid et.al., 2000.

c

Grossfield et al., 2003.

d

Yu et al., 2010a

e

Noskov et al., 2004.

f

Varma and Rempe, 2008.

g

Noskov and Roux, 2008.

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