Quasi-chemical theory for anion hydration and specific ion effects:<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si36.svg"><mml:mrow><mml:msup><mml:mrow><mml:mi mathvariant="normal">Cl</mml:mi></mml:mrow><mml:mrow><mml:mo>-</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>(aq) vs.<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si37.svg"><mml:mrow><mml:msup><mml:mrow><mml:mi mathvariant="normal">F</mml:mi></mml:mrow><mml:mrow><mml:mo>-</mml:mo></mml:mrow></mml:msup></m

Muralidharan, Ajay; Pratt, Lawrence R.; Chaudhari, Mangesh I.; Rempe, Susan

doi:10.1016/j.cpletx.2019.100037

Cited by 22 publications

(60 citation statements)

References 123 publications

(196 reference statements)

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“…Therefore, it may not be very surprising that the stability of the water wire in gA is not optimally modeled by these water models. Recent ab initio MD simulations have shown that, while interacting with a chloride ion, the water dipole flips rapidly on the picosecond timescale, but, with a fluoride ion where the proton approaches more closely, the water dipole becomes stable (50). This work hints that a quantum treatment of the water wire in the gA pore, where waters are restricted in orientation to form strong interactions with carbonyls, may have a much longer lifetime than in the classical MD simulations.…”

Section: Resultsmentioning

confidence: 92%

Functional stability of water wire–carbonyl interactions in an ion channel

Paulino

Hung

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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Water wires are critical for the functioning of many membrane proteins, as in channels that conduct water, protons, and other ions. Here, in liquid crystalline lipid bilayers under symmetric environmental conditions, the selective hydrogen bonding interactions between eight waters comprising a water wire and a subset of 26 carbonyl oxygens lining the antiparallel dimeric gramicidin A channel are characterized by17O NMR spectroscopy at 35.2 T (or 1,500 MHz for1H) and computational studies. While backbone15N spectra clearly indicate structural symmetry between the two subunits, single site17O labels of the pore-lining carbonyls report two resonances, implying a break in dimer symmetry caused by the selective interactions with the water wire. The17O shifts document selective water hydrogen bonding with carbonyl oxygens that are stable on the millisecond timescale. Such interactions are supported by density functional theory calculations on snapshots taken from molecular dynamics simulations. Water hydrogen bonding in the pore is restricted to just three simultaneous interactions, unlike bulk water environs. The stability of the water wire orientation and its electric dipole leads to opposite charge-dipole interactions for K+ions bound at the two ends of the pore, thereby providing a simple explanation for an ∼20-fold difference in K+affinity between two binding sites that are ∼24 Å apart. The17O NMR spectroscopy reported here represents a breakthrough in high field NMR technology that will have applications throughout molecular biophysics, because of the acute sensitivity of the17O nucleus to its chemical environment.

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Section: Resultsmentioning

confidence: 92%

Functional stability of water wire–carbonyl interactions in an ion channel

Paulino

Hung

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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“…The polar character of water leads to the dissociation of salts in aqueous solution and the dispersion of the resulting ions. The solvation of anions through hydrogen bonding in aqueous solution [2] has been investigated theoretically for a number of anions [3,4], including Fand Cl - [5][6][7][8][9], BF 4 - [10] and PF 6 - [11]. Among the myriad of possible anions, we have turned our attention to BeF 3 -1 and BeF 4 -2 .…”

Section: Introductionmentioning

confidence: 99%

Microsolvation of the Be-F bond in complexes of BeF₂, BeF₃^–1, and BeF₄^–2with nH₂O, forn = 1–6

2021

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Ab initio MP2/aug'-cc-pVTZ calculations have been carried out to determine the structures and binding energies of complexes of BeF 2 , BeF 3 -1 , and BeF 4 -2 with n H 2 O molecules, with n = 1-6. For each series of complexes with BeF 2 , BeF 3 -1 , and BeF 4 -2 , the binding energies increase as the number of water molecules increases, but the binding energies per intermolecular bond for complexes formed between BeF 2 and BeF 4 -2 and nH 2 O decrease as the number of water molecules increases. The binding energies per bond of the BeF 3 -1 complexes show little dependence on the number of H 2 O molecules present. Intermolecular O-H ... F hydrogen bonds (HB) stabilise all complexes of H 2 O with the beryllium bases except for BeF 2 :1H 2 O and BeF 2 :2H 2 O. Complexes of BeF 2 are also stabilised by O ... Be beryllium bonds (BeB) and O-H ... O hydrogen bonds. EOM-CCSD calculations have also been performed to determine the spin-spin coupling constants. The one-bond coupling constants 1 J(Be-F) increase as the Be-F distance decreases, and exhibit an excellent second-order correlation with that distance. 2h J(O-F) coupling constants across O-H ... F hydrogen bonds also exhibit a secondorder dependence on distance. Coupling constants 1be J(O-Be) and 2h J(O-O) are found in complexes with BeF 2 and exhibit a linear dependence on the Be-O and O-O distances, respectively.

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“…Important aspects of those mecha-23 nisms in aqueous solution involves the local ion hydration properties, and exchange of 24 hydrating water molecules for molecular ligating groups [3,5,[10][11][12]. As a step toward 25 enhancing our understanding of ion-specific effects, this paper studies the structures 26 and free energies of hydration clusters of the anions F − , Cl − , Br − , and I − in the dilute 27 gas-phase, with the longer term goal of addressing the comparative behavior of this se-28 ries of ions in liquid water on the basis of quasi-chemical theory (QCT) [12][13][14][15]. Accurate 29 characterization of gas-phase clusters can indeed helpfully inform QCT applications, 30 and has been successful for cations [12].…”

Section: Introduction 17mentioning

confidence: 99%

“…We compared: i) the experimental values determined from mass spectrometry [45]: ii) 85 the quantum-mechanical rigid rotor harmonic oscillator approximation (Figure 1), and 86 iii) the rough-energy landscape procedure proposed in Ref [15]. Figure 2 summarizes all 87 results graphically.…”

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confidence: 99%

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Free Energies of Hydrated Halide Anions: High throughput Computations on Clusters to Treat Rough Energy-Landscapes

Gomez¹,

Pratt²,

Rogers³

et al. 2021

Preprint

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With a longer-term goal of addressing the comparative behavior of the aqueous halides F$^-$, Cl$^-$, Br$^-$, and I$^-$ on the basis of quasi-chemical theory (QCT), here we study structures and free energies of hydration clusters for those anions. We confirm that energetically optimal $(\mathrm{H_2O})_n\mathrm{X}$ clusters, with X = Cl$^-$, Br$^-$, and I$^-$, exhibit \emph{surface} hydration structures. Computed free energies based on optimized surface hydration structures utilizing a harmonic approximation, typically (but not always) disagree with experimental free energies. To remedy the harmonic approximation, we utilize single-point electronic structure calculations on cluster geometries sampled from an AIMD (\emph{ab initio} molecular dynamics) simulation stream. This \emph{rough-landscape} procedure is broadly satisfactory and suggests unfavorable ligand crowding as the physical effect corrected. Nevertheless, this procedure can break down when $n \gtrsim 4$, with the characteristic discrepancy resulting from a relaxed definition of clustering in the identification of $(\mathrm{H_2O})_n\mathrm{X}$ clusters, including ramified structures natural in \emph{physical cluster theories.} With ramified structures, the central equation for the present rough-landscape approach can acquire some inconsistency. Extension of these physical cluster theories in the direction of QCT should remedy that issue, and should be the next step in this research direction.

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Quasi-chemical theory for anion hydration and specific ion effects:Cl-(aq) vs.F-

Cited by 22 publications

References 123 publications

Functional stability of water wire–carbonyl interactions in an ion channel

Functional stability of water wire–carbonyl interactions in an ion channel

Microsolvation of the Be-F bond in complexes of BeF₂, BeF₃^–1, and BeF₄^–2with nH₂O, forn = 1–6

Free Energies of Hydrated Halide Anions: High throughput Computations on Clusters to Treat Rough Energy-Landscapes

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Quasi-chemical theory for anion hydration and specific ion effects:Cl-(aq) vs.F-

Cited by 22 publications

References 123 publications

Functional stability of water wire–carbonyl interactions in an ion channel

Functional stability of water wire–carbonyl interactions in an ion channel

Microsolvation of the Be-F bond in complexes of BeF2, BeF3–1, and BeF4–2with nH2O, forn = 1–6

Free Energies of Hydrated Halide Anions: High throughput Computations on Clusters to Treat Rough Energy-Landscapes

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Microsolvation of the Be-F bond in complexes of BeF₂, BeF₃^–1, and BeF₄^–2with nH₂O, forn = 1–6