The electrostatic energy of dipole molecules in different media

Bell, R. P.

doi:10.1039/tf9312700797

Cited by 83 publications

(43 citation statements)

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“…⌽ RF ͑r i ͒ is the so-called "reaction field" potential, that is the electric field generated by the polarization of the dielectric continuum induced by the molecular charge distribution. Since the works of Bell 21 and Onsager 22 in the 1930s, many different approaches have been developed to describe this phenomenon. 23,24 Within the continuum approximations, the reaction field and its potential can be expressed analytically using the multipole expansion of the charge distribution 20 and the generalized Born theory 25 or numerically by solving the Poisson equation with either the finite difference method 26,27 or the boundary element ͑BE͒ method.…”

Section: B Electrostatic Term "Reaction Field…mentioning

confidence: 99%

A mean field approach for molecular simulations of fluid systems

Brancato

Nola

Barone

et al. 2005

The Journal of Chemical Physics

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In this paper we introduce a mean field method for simulating complex molecular systems like liquids and solutions. Using well-established theoretical principles and models, we obtained a relatively simple approach which seems to provide a reliable description of the bulk molecular behavior of liquid water. Moreover, we have applied this approach to study simple solutes in solution, like sodium and chloride ions and acetone. Comparison with standard simulations, performed with periodic boundary conditions, shows that such a mean field method can reproduce the same structural and thermodynamical properties at low computational costs and represents a valid alternative for simulating solute-solvent systems, like solutions of large biomolecules.

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Section: B Electrostatic Term "Reaction Field…mentioning

confidence: 99%

A mean field approach for molecular simulations of fluid systems

Brancato

Nola

Barone

et al. 2005

The Journal of Chemical Physics

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“…47,48 The assumption is one of a nonpolarizable point dipole isolated in the center of a cavity in a uniform dielectric medium. The spectral shift in energy is then given by 49 where is the static dielectric constant of the solvent (for argon at high pressure see ref 50), ∆(µ 2 ) is the difference in the squares of the ground-and excited-state dipole moments, and a is the diameter of the cavity, which we assume to be pressure independent.…”

Section: Preliminariesmentioning

confidence: 99%

Solvation Ultrafast Dynamics of Reactions. 12. Probing along the Reaction Coordinate and Dynamics in Supercritical Argon

1996

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In this paper, our focus is on the influence of the solvent density on the caging, recombination dynamics, and the nature of the reaction coordinate of iodine in supercritical argon at pressures of 0-2500 bar. Femtosecond probing with widely tunable pulses allows us to directly resolve the geminate recombination of iodine atoms and the subsequent relaxation processes. A nonzero recombination yield is found at argon pressures as low as 200 bar, and this yield increases strongly with increasing solvent density. The mechanism involves recombination onto the A/A′ states. At high pressures, a large fraction of the iodine atoms undergo an ultrafast "in-cage" recombination which is measured on the subpicosecond time scale at 2500 bar of argon. In addition, a fraction of the iodine atoms break through the solvent cage and begin a diffusive motion through the raregas solvent. Experimental evidence is presented and indicates that this diffusive motion leads to reencounters and subsequent recombination of the geminate iodine pair. This diffusive recombination occurs on a significantly longer time scale than the rapid "in-cage" recombination. The newly-formed iodine molecules undergo vibrational relaxation within the A/A′ state, and the dynamics of this process and its dependence on the solvent density are revealed. A key concept here is the solvent density-induced control of the rigidity of the first solvent shell surrounding the dissociating iodine atoms. As shown before [Liu et al. Nature 1993, 364, 427], such studies of solvation present a unique opportunity of examining the microscopic influence of the solvent structure on reaction dynamics in clusters and solutions.

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“…Channel-forming Potencies and Single-channel Lifetimes It is energetically unfavorable to transfer dipolar groups into low dielectric media (Bell, 1931), although factors other than the dipole moment may be significant for determining the partition energy. The variations in channel-forming potencies and average single-channel lifetimes are qualitatively consistent with the predictions of such a simple electrostatic argument.…”

Section: Ion Permeationmentioning

confidence: 99%

Single-channel studies on linear gramicidins with altered amino acid side chains. Effects of altering the polarity of the side chain at position 1 in gramicidin A

Russell¹,

Weiss²,

Navetta³

et al. 1986

Biophysical Journal

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The modulation of gramicidin A single-channel characteristics by the amino acid side chains was investigated using gramicidin A analogues in which the NH2 terminal valine was chemically replaced by other amino acids. The replacements were chosen such that pairs of analogues would have essentially isosteric side chains of different polarities at position 1 (valine vs. trifluorovaline or hexafluorovaline; norvaline vs. S-methyl-cysteine; and norleucine vs. methionine). Even though the side chains are not in direct contact with the permeating ions, the single-channel conductances for Na+ and Cs+ are markedly affected by the changes in the physico-chemical characteristics of the side chains. The maximum single-channel conductance for Na+ is decreased by as much as 10-fold in channels formed by analogues with polar side chains at position 1 compared with their counterparts with nonpolar side chains, while the Na+ affinity is fairly insensitive to these changes. The relative conductance changes seen with Cs+ were less than those seen with Na+; the ion selectivity of the channels with polar side chains at position 1 was increased. Hybrid channels could form between compounds with a polar side chain at position 1 and either valine gramicidin A or their counterparts with a nonpolar side chain at position 1. The structure of channels formed by the modified gramicidins is thus essentially identical to the structure of channels formed by valine gramicidin A. The polarity of the side chain at position 1 is an important determinant of the permeability characteristics of the gramicidin A channel. We discuss the importance of having structural information when interpreting the functional consequences of site-directed amino acid modifications.

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The electrostatic energy of dipole molecules in different media

Cited by 83 publications

References 0 publications

A mean field approach for molecular simulations of fluid systems

A mean field approach for molecular simulations of fluid systems

Solvation Ultrafast Dynamics of Reactions. 12. Probing along the Reaction Coordinate and Dynamics in Supercritical Argon

Single-channel studies on linear gramicidins with altered amino acid side chains. Effects of altering the polarity of the side chain at position 1 in gramicidin A

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