Nonpolar solvation

Giesen, D. J., Storer, J., Cramer, C. J. and Truhlar, D. J. General semiempirical quantum mechanical solvation model for nonpolar solvation free energies, n-hexadacane., J.Am. Chem.Soc., 117 (1995), 1057-1068... 

A further motivation of this study comes from the following observations. Many chemical dynamic processes, such as nonpolar solvation dynamics [70], can be described in terms of the frequency-dependent viscosity because... 

K. Ando and S. Kato, Dielectric relaxation dynamics of water and methanol solutions associated with the ionization of /V,/V-dimcltiylanilinc theoretical analyses, J. Chem. Phys., 95 (1991) 5966-82 D. K. Phelps, M. J. Weaver and B. M. Ladanyi, Solvent dynamic effects in electron transfer molecular dynamics simulations of reactions in methanol, Chem. Phys., 176 (1993) 575-88 M. S. Skaf and B. M. Ladanyi, Molecular dynamics simulation of solvation dynamics in methanol-water mixtures, J. Phys. Chem., 100 (1996) 18258-68 D. Aheme, V. Tran and B. J. Schwartz, Nonlinear, nonpolar solvation dynamics in water the roles of elec-trostriction and solvent translation in the breakdown of linear response, J. Phys. Chem. B, 104 (2000) 5382-94. 

A mode coupling theory is recently developed [135] which goes beyond the time-dependent density functional theory method. In this theory a projection operator formalism is used to derive an expression for the coupling vertex projecting the fluctuating transition frequency onto the subspace spanned by the product of the solvent self-density and solvent collective density modes. The theory has been applied to the case of nonpolar solvation dynamics of dense Lennard-Jones fluid. Also it has been extended to the case of solvation dynamics of the LJ fluid in the supercritical state [135],... 

Figure 2 Normalized instantaneous-normal-mode spectra for high-density supercritical Ar. The overall density of states (DOS) is contrasted with three different INM influence spectra for a diatomic solute for rotational friction, vibrational friction, and (nonpolar) solvation dynamics. Only the spectrum of modes for vibrational friction is of direct relevance to this chapter, but the other influence spectra show the strong similarities in the instantaneous solvent dynamics associated with different kinds of solute relaxation.

The nonpolar solvation free energy is given by the sum of two terms the free energy to form the cavity in solvent filled by the solute and the dispersion attraction between solute and solvent [65,113]. The nonpolar free energy is written as [27]... 

A General Semiempirical Quantum Mechanical Solvation Model for Nonpolar Solvation Free Energies. n-Hexadecane. 

These experiments have shown that the slower component of solvation is linked to the overall structural dynamics of the liquid, and that mode coupling theory predicts many of the overall features of these dynamics. Dielectric solvation, which is the most widely studied solvation mechanism, does not play a major role for this nonpolar solute. Two theories of nonpolar solvation give better agreement with the data. Bagchi s theory is more rigorously derived, but our model permits a more detailed and rigorous comparison with experiment. 

GB/S A Generalized-Born/Surface-Area. A method for simulating solvation implicitly, developed by W.C. Still s group at Columbia University. The solute-solvent electrostatic polarization is computed using the Generalized-Born equation. Nonpolar solvation effects such as solvent-solvent cavity formation and solute-solvent van der Waals interactions are computed using atomic solvation parameters, which are based on the solvent accessible surface area. Both water and chloroform solvation can be emulated. 

Chen, J., Brooks III, C.L. Implicit modeling of nonpolar solvation for simulating protein folding and conformational transitions. Phys. Chem. Chem. Phys. 2008,10,471-81. 

Lee, M. S., and Olson, M. A. (2013). Comparison of volume and surface area nonpolar solvation free energy terms for implicit solvent simulations,/. Chem. Phys. 139, pp. 044119 1-6. 

As mentioned above, a parallel line of research has been carried out by Dzubiella, Hansen, McCammon, and Li. Early work by Dzubiella and Hansen demonstrated the importance of the self-consistent treatment of polar and nonpolar interactions in solvation models [137, 138]. These observations were then incorporated into a self-consistent variational framework for polar and nonpolar solvation behavior by Dzubiella, Swanson, and McCammon [131, 139] which shared many common elements with our earlier geometric flow approach but included an additional term to represent nonpolar energetic contributions from surface curvature. Li and co-workers then developed several mathematical methods for this variational framework based on level-set methods and related approaches [140-142] which they demonstrated and tested on a... 

Therefore, we have the following nonpolar solvation free energy functional [1,71,74] ... 

The accuracy of the nonpolar solvation model performance is crucial to the success of other expanded versions of the differential geometry formalism. In particular, as the electrostatic effect and its associated approximation error are excluded, the major factor impacting the nonpolar solvation model is the solvent-solute boundary, which is governed by the DG-based formalism. Therefore, the nonpolar model provides the most direct and essential validation of the DG-based models. In our recent work [1], the DG-based nonpolar solvation (DG-NP) model was tested using a... 

Table 12.1 Solvation energies calculated with the differential geometry nonpolar solvation model for a set of 11 alkanes in comparison with an explicit solvent model [154]...

This is not anticipated from cavity hydrophobicity considerations of nonpolar solvation. We need to use our new pictures/theories of the mechanisms to explain this, as clearly the traditional hydrophobicity plus electrostatics picture is not quantitatively helpful in explaining the experimental data and simulations at this level. 

The Hofmeister Series Nonpolar Solvation in Salt Solutions... 

At the most complex level we use equation (24) to present the results in the form of Table 5. Table 5 shows the inhibitor-enzyme (column 2) and enzyme components (column 3) of the relative binding free energy. These are then divided into sub components. The sub components are the molecular mechanics terms (E, row 1 beneath inhibitor), solute entropy terms (-TS, ,, row 2 beneath inhibitor), electrostatic solvation free energy terms (AG, row 3 beneath inhibitor), nonpolar solvation terms (AG , row 4 beneath inhibitor), and the total solution phase free energy (G, row 5 beneath inhibitor). Column 4 of the table gives the total values for all sub components, these are obtained by summing columns 2 and 3 for a particular subcomponent. 

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