Accounting for electronic polarization in non-polarizable force fields

Leontyev, Igor; Stuchebrukhov, Alexei A.

doi:10.1039/c0cp01971b

Cited by 434 publications

(669 citation statements)

References 74 publications

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“…20 Polarizability can be treated phenomenologically by reducing the charges by a scaling factor that depends on the solvent's dielectric constant, in a method termed electronic continuum correction (ECC) or molecular dynamics in an electronic continuum (MDEC). 21,22 This results in ions that have charges of around ±0.7 e to ±0.9 e. 14,21,22 Treating the charges as variational parameters leads to charges of ±0.80 e. 18 These values are close to those that result from charge transfer to the solvent. [23][24][25][26][27] However, in the charge transfer models, unlike in ECC, all ions are not necessarily reduced in charge by the same amount, the charge of an ion fluctuates in time, and the water acquires transient charges.…”

Section: Introductionmentioning

confidence: 69%

The influence of polarizability and charge transfer on specific ion effects in the dynamics of aqueous salt solutions

Nguyen

Rick

2018

The Journal of Chemical Physics

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A relationship between the effect of uni-univalent electrolytes on the structure of water and on its volatility The Journal of Chemical Physics 148, 222807 (2018) The influence of polarizability and charge transfer on specific ion effects in the dynamics of aqueous salt solutions The diffusion rates for water molecules in salt solutions depend on the identity of the ions, as well as their concentration. Among the alkali metal ions, cesium and potassium increase and sodium strongly decreases the diffusion constant of water. The origin of the difference can be understood by examining the simulation results using different potential models. In this work, aqueous solutions of salts are simulated with a variety of models. Commonly used non-polarizable models, which otherwise reproduce many experimental properties, do not capture the trend in the diffusion constant, while models which include polarization and/or charge transfer interactions do. For the non-polarizable models, the diffusion constant decreases too strongly with salt concentration. The changes in the water diffusion constant with increasing salt concentration match the diffusion constant of the ion. The ion diffusion constant is dependent on the residence time for water in the ion solvation shell. The non-polarizable models over-estimate the residence time, relative to the translational diffusion constant and so tend to under-estimate the ion and water diffusion constants. Published by AIP Publishing.

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Section: Introductionmentioning

confidence: 69%

The influence of polarizability and charge transfer on specific ion effects in the dynamics of aqueous salt solutions

Nguyen

Rick

2018

The Journal of Chemical Physics

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“…In this respect, it is interesting to note that three recent approaches for improving the description of ion-water interactions at the MM level rely in effect on a weakening of the ion-solvent Coulombic interactions. These are: the induction-type 66,67,104,107,[278][279][280][281]284 force fields, where CT effects are included explicitly, the molecular dynamics in electric continuum (MDEC) approach, [285][286][287] where the ion charge is effectively scaled 75,[77][78][79]288 by a factor of about 0.7-0.9 (in line with QM results 282 ), and the multisite ion description, [289][290][291][292][293][294][295] where the ion charge is redistributed over virtual off-center sites within the ion. The observation made here that the features of the QM/MM RDFs can be reproduced more accurately with a MM model when reducing the nominal charge of the ion to +0.75 e is perfectly in line with these considerations.…”

Section: Discussionmentioning

confidence: 99%

Absolute proton hydration free energy, surface potential of water, and redox potential of the hydrogen electrode from first principles: QM/MM MD free-energy simulations of sodium and potassium hydration

Hofer

Hünenberger

2018

The Journal of Chemical Physics

104

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The absolute intrinsic hydration free energy G • H + ,wat of the proton, the surface electric potential jump χ • wat upon entering bulk water, and the absolute redox potential V • H + ,wat of the reference hydrogen electrode are cornerstone quantities for formulating single-ion thermodynamics on absolute scales. They can be easily calculated from each other but remain fundamentally elusive, i.e., they cannot be determined experimentally without invoking some extra-thermodynamic assumption (ETA). The Born model provides a natural framework to formulate such an assumption (Born ETA), as it automatically factors out the contribution of crossing the water surface from the hydration free energy. However, this model describes the short-range solvation inaccurately and relies on the choice of arbitrary ion-size parameters. In the present study, both shortcomings are alleviated by performing first-principle calculations of the hydration free energies of the sodium (Na + ) and potassium (K + ) ions. The calculations rely on thermodynamic integration based on quantum-mechanical molecular-mechanical (QM/MM) molecular dynamics (MD) simulations involving the ion and 2000 water molecules. The ion and its first hydration shell are described using a correlated ab initio method, namely resolution-of-identity second-order Møller-Plesset perturbation (RIMP2). The next hydration shells are described using the extended simple point charge water model (SPC/E). The hydration free energy is first calculated at the MM level and subsequently increased by a quantization term accounting for the transformation to a QM/MM description. It is also corrected for finite-size, approximate-electrostatics, and potentialsummation errors, as well as standard-state definition. These computationally intensive simulations provide accurate first-principle estimates for G • H + ,wat , χ • wat , and V • H + ,wat , reported with statistical errors based on a confidence interval of 99%. The values obtained from the independent Na + and K + simulations are in excellent agreement. In particular, the difference between the two hydration free energies, which is not an elusive quantity, is 73.9 ± 5.4 kJ mol 1 (K + minus Na + ), to be compared with the experimental value of 71.7 ± 2.8 kJ mol 1 . The calculated values of G • H + ,wat , χ • wat , and V • H + ,wat ( 1096.7 ± 6.1 kJ mol 1 , 0.10 ± 0.10 V, and 4.32 ± 0.06 V, respectively, averaging over the two ions) are also in remarkable agreement with the values recommended by Reif and Hünenberger based on a thorough analysis of the experimental literature ( 1100 ± 5 kJ mol 1 , 0.13 ± 0.10 V, and 4.28 ± 0.13 V, respectively). The QM/MM MD simulations are also shown to provide an accurate description of the hydration structure, dynamics, and energetics. Published by AIP Publishing.

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“…4). Further, compensation of missing electronic polarizability by scaling the ion charge 112,114 76 significantly reduced Ca 2+ binding in CHARMM36 (Fig. 6), however, the model must be further analysed to fully interpret the results.…”

Section: Cation Binding In Different Simulation Modelsmentioning

confidence: 99%

“…Potential candidates are, e.g., discrepancies in the ion models [109][110][111] , incomplete treatment of electronic polarizability 112 , and inaccuracies in the lipid headgroup description 45 .…”

Section: Cation Binding In Different Simulation Modelsmentioning

confidence: 99%

Molecular electrometer and binding of cations to phospholipid bilayers

Catte

Girych

Javanainen

et al. 2016

Phys. Chem. Chem. Phys.

256

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Despite the vast amount of experimental and theoretical studies on the binding affinity of cations -especially the biologically relevant Na + and Ca 2+ -for phospholipid bilayers, there is no consensus in the literature. Here we show that by interpreting changes in the choline headgroup order parameters according to the 'molecular electrometer' concept [Seelig et al., Biochemistry, 1987, 26, 7535], one can directly compare the ion binding affinities between simulations and experiments. Our findings strongly support the view that in contrast to Ca 2+ and other multivalent ions, Na + and other monovalent ions (except Li + ) do not specifically bind to phosphatidylcholine lipid bilayers at sub-molar concentrations. However, the Na + binding affinity was overestimated by several molecular dynamics simulation models, resulting in artificially positively charged bilayers and exaggerated structural effects in the lipid headgroups. While qualitatively correct headgroup order parameter response was observed with Ca 2+ binding in all the tested models, no model had sufficient quantitative accuracy to interpret the Ca 2+ :lipid stoichiometry or the induced atomistic resolution structural changes. All scientific contributions to this open collaboration work were made publicly, using nmrlipids.blogspot.fi as the main communication platform.

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Accounting for electronic polarization in non-polarizable force fields

Cited by 434 publications

References 74 publications

The influence of polarizability and charge transfer on specific ion effects in the dynamics of aqueous salt solutions

The influence of polarizability and charge transfer on specific ion effects in the dynamics of aqueous salt solutions

Absolute proton hydration free energy, surface potential of water, and redox potential of the hydrogen electrode from first principles: QM/MM MD free-energy simulations of sodium and potassium hydration

Molecular electrometer and binding of cations to phospholipid bilayers

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