Yx. Sun et al., MOLECULAR-DYNAMICS AND FREE-ENERGY PERTURBATION STUDY OF SPHERAND COMPLEXATION WITH METAL-IONS EMPLOYING ADDITIVE AND NONADDITIVE FORCE-FIELDS, Journal of physical chemistry, 99(25), 1995, pp. 10081-10085
Molecular dynamics and free energy perturbation have been applied to s
tudy the complexation and the selectivity of a host molecule hexaaniso
le spherand (1) with its metal ion ligands, Two different potential fu
nction force fields were tested: a two-body interactive potential with
the TIP3P water model and a recently derived polarizable and three-bo
dy interactive potential including a polarizable water model. Our resu
lts show that the two-body additive potential is able to provide usefu
l information on the relative binding affinities of alkali metal ions,
although for the Na+ --> Li+ case the agreement with experiment is on
ly qualitative. The relative binding free energy of Li+ and Na with th
e hexaanisole spherand is calculated to be -2.7 kcal/mol, compared to
the experimental value of < -3.8 kcal/mol. The agreement improved when
the mole sophisticated polarizable and three-body interactive potenti
al force field was employed, resulting in a relative binding free ener
gy of Li+ and Na+ of -3.7 kcal/mol. We have also tested different elec
trostatic charge fitting protocols and models, and the results showed
that the choice of protocol is of critical importance for obtaining qu
antitative agreement with experiment.