Approximate evaluations of the electrostatic free energy and internal energy changes in solution processes

Miertus, Stanislav; Tomasi, Jacopo

doi:10.1016/0301-0104(82)85072-6

Cited by 2,342 publications

(748 citation statements)

References 14 publications

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“…Existing continuum models, e.g. the polarizable continuum model, takes into account the influence of the solvent through an effective dielectric constant [41,42,43]. The solvation model density (SMD) by Marenich et al [44] provides another alternative to handle these effects.…”

Section: Atomic Charges Via Ab Initio Computationsmentioning

confidence: 99%

A New Force Field of Formamide and the Effect of the Dielectric Constant on Miscibility

Luz

Méndez-Maldonado

Núñez-Rojas

et al. 2015

J. Chem. Theory Comput.

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Current force fields underestimate significantly the dielectric constant of formamide at standard conditions. We present a derivation of an accurate potential for formamide, which functional form builds on the OPLS/AA force field. Our procedure follows the approach introduced by Salas et al. (J. Chem. Theory and Comp., Just accepted, 2015), that can use information from ab initio calculations and molecular dynamics simulations. We consider several strategies to derive the atomic charges of formamide. We find that the inclusion of polarization effects in the quantum mechanical computations is essential to obtain reliable force fields. By varying the atomic charges and the LennardJones parameters describing the dispersion interactions in the OPLS/AA force field, we derive an optimum set of parameters to obtain accurate results for the dielectric constant, surface tension and bulk density of liquid formamide in a wide range of thermodynamic states. We test the transferability of our parameters to investigate liquid/liquid mixtures. We have chosen as case study an equimolar mixture of formamide and hexan-2-one. This mixture involves two fluids with very different polar characteristics, namely, large differences in their dielectric constants and their performance as polar solvents. The new potential highlights the importance of the correct parametrization of the pure liquid phases to investigate liquid mixtures. Finally, we examine the microscopic origin of the observed inmiscibility between formamide and hexa-2-one.

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Section: Atomic Charges Via Ab Initio Computationsmentioning

confidence: 99%

A New Force Field of Formamide and the Effect of the Dielectric Constant on Miscibility

Luz

Méndez-Maldonado

Núñez-Rojas

et al. 2015

J. Chem. Theory Comput.

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“…The free energies of solvation were determined using a semiempirical adapted version (Negre et al, 1992;Luque et al, 1994) of the SCRF developed by Miertus, Scrocco, and Tomasi (MST) (Miertus et al, 1981;Miertus and Tomasi, 1982). According to this method, the free energy of solvation was determined by addition of electrostatic and steric contributions [Eqn (3)], where the latter was computed as the sum of cavitation and van der Waals terms.…”

Section: Gas Phase Conformations Conformational Preferences Ofmentioning

confidence: 99%

Intrinsic Conformational Preferences of the Hoechst Dye Family and their Influence on DNA Binding

Vega

Coll

Alemán

1996

European Journal of Biochemistry

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Quantum mechanical calculations have been used to investigate the molecular conformation of the Hoechst family of DNA-binding dyestuffs. Compounds in which the phenolic substituent adopts either a meta or (tam position were studied. Two different environments have been considered, which are the gas phase and aqueous solution; the conformation in aquaeous solution has been modeled through a selfconsistent reaction field strategy. The results clearly indicate that Hoechst dyes do not adopt a planar conformation and that the degree of planarity is controlled by the external environment. A comparison with experimental data reveals that the conformation of Hoechst dyes in the gas phase is similar to that observed in DNA complexes by X-ray crystallography. In aqueous solution, the conformation deviates from planarity more than in the gas phase, since non-bonded interactions with the solvent offset the loss of conjugative interactions. The role of the drug conformation in the binding mechanism with DNA is discussed.

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“…They make up proteins and therefore are called the building blocks of the default convergence criteria. To analyze the solvent effects on all the species involved in the proposed ionization reactions, the polarized continuum model (PCM) of Tomasi's et al is used [32].…”

Section: Resultsmentioning

confidence: 99%

Determination of acidic dissociation constants of glutamine and isoleucine in water using ab initio methods

Koohyar¹

2014

Turk J Bioch

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Determination of acidic dissociation constants of glutamine and isoleucine in water using ab initio methods [Ab initio yöntemler kullanılarak glutamin ve izolösinin sudaki asidik ayrışma sabitlerinin saptanması] ABSTRACT Objective: In this study, pKa values of glutamine and isoleucine were determined in aqueous solution by ab initio and DFT methods. To explain the obtained values of pKa, the molecular conformations and solute-solvent interactions of the anions, cations, and neutrals molecules of glutamine and isoleucine were investigated. The experimental determination of these values, apart from been laborious, is a challenge because of the low water solubility of these compounds. Methods: We have evaluated different models to determination of pKa, using the density functional theory (DFT) method at the B3LYP level of the theory. Results: this study shows the several ionization reactions and equilibriums in protic solvent, which possess a high hydrogen-band-donor capability. These reactions and equilibriums constitute the indispensable theoretical basis for calculation of glutamine and isoleucine acidity constants. Tomasi's method was used to analyze the formation of intermolecular hydrogen bonds between the existent species and water molecules. In this way, it is proposed that in alkaline aqueous solutions the cation, anion, and neutral species of glutamine and isoleucine are solvated with one, two, three, and four molecules of water, respectively. In this study, there is comparable agreement between the experimental and calculated pKa values for the acid-base reactions proposed. Conclusion: In this paper, The calculations performed at the B3LYP/6-31+G(d) levels of theory using Tomasi's method allowed us to prove that cations, neutral molecules, and anions form IHBs with some molecules of water. It is shown that, theoretically calculated pKa values are in good agreement with the existing experimental pKa values, which are determined from potentiometric titration and UV-visible spectrophotometric measurements. Key Words: Ab initio method, DFT method, ionization constant, isoleucine, glutamine Conflict of Interest: Authors have no conflict of interest. ÖZETAmaç: Çalışmada ab initio ve DFT yöntemleri kullanılarak glutamin ve izolösinin sulu çözel-tideki pKa değerleri saptanmıştır. Elde edilen pKa değerlerini açıklamak amacıyla glutamin ve izolösinin anyon, katyon ve nötral moleküllerinin moleküler konformasyonları ve çözünen-çö-zücü etkileşimleri incelenmiştir. Bu değerlerin deneysel tayini zahmetli olmasının yanı sıra, bu moleküllerin suda çözünürlüğünün az olması nedeniyle oldukça güçtür. Metod: pKa tayini için, B3LYP düzeyinde yoğunluk işlevsel teorisi (density functional theory-DFT) kullanılarak farklı modeller değerlendirilmiştir. Bulgular: Çalışma, yüksek hidrojen-bağı-verici kapasiteye sahip olan protik çözücü içerisinde çeşitli iyonizasyon tepkimelerini ve dengeyi göstermektedir. Bu tepkimeler ve denge glutamin ve izolösinin asitlik sabitlerinin hesaplanması için teorik temel oluşturmaktadır. Varolan türl...

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Approximate evaluations of the electrostatic free energy and internal energy changes in solution processes

Cited by 2,342 publications

References 14 publications

A New Force Field of Formamide and the Effect of the Dielectric Constant on Miscibility

A New Force Field of Formamide and the Effect of the Dielectric Constant on Miscibility

Intrinsic Conformational Preferences of the Hoechst Dye Family and their Influence on DNA Binding

Determination of acidic dissociation constants of glutamine and isoleucine in water using ab initio methods

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