Semiclassical-Continuum Approach to the Electrostatic Free Energy of Solvation

Abstract

A new semiclassical continuum approach for computation of the electrostatic contribution to the free energy of solvation is presented. The method is based on a first-order perturbation treatment of the linear response approximation for the solvent effect. The expression for the electrostatic free energy of solvation afforded by the perturbative approach is formally similar to the classical continuum algorithm reported by Miertus, Scrocco, and Tomasi. Nevertheless, the semiclassical approach allows an accurate, inexpensive treatment of polarization effects, which relies on the use of two sets of partial charges for description of the solute-solvent interactions. The two sets of charges reflect the charge distribution of the solute in the gas phase and fully relaxed in solution. Particular attention is paid to the parametrization of the partial charges. The results determined by using the semiclassical approach for a series of prototypical neutral polar molecules, for selected amino acid residues in neutral and zwitterionic states, and for several test calculations on peptides are very close to the values determined from quantum mechanical self-consistent reaction field calculations. These encouraging results allow us to examine the potential application of the semiclassical treatment as a fast procedure for the inclusion of solvent polarization effects in force-field-derived methods.

Hydrophobic similarity between molecules: A MST‐based hydrophobic similarity index

“…(5)] is not so simple due to its dependence on the solute Hamiltonian. However, this difficulty is eliminated by using a first-order perturbation treatment of the solvation free energy, [62][63][64][65] which allows us to express the electrostatic free energy as half the interaction energy between the solute having the nonpolarized charge distribution and the fully polarized solvent reaction field [eq. (11)].…”

General and Theoretical Aspects of Phenols

“…1645.9 39 A νC 1 C 6 (23), νC 3 C 4 (17), νC 2 C 3 (13), νC 5 140, 197 -201 . This property and the relevant reaction will be discussed in a subsequent section.…”

“…The antioxidant property can be related to the readily abstractable phenolic hydrogen as a consequence of the relatively low bond dissociation enthalpy of the phenolic O−H group [BDE(O−H)]. A large variety of ortho-and/or para-alkoxy-substituted phenols have been identified as natural antioxidants, such as α-tocopherol (13), which is known as the most effective lipid-soluble chain-breaking antioxidant in human blood plasma, and ubiquino-10 (14), both present in low-density lipid proteins. The mechanism of action of many phenolic antioxidants relies on their ability to transfer the phenolic H atom to a chain-carrying peroxyl radical at a rate much faster than that at which the chain-propagating step of lipid peroxidation proceeds 73 -77 .…”

“…The TS τ structure is the transition state governing the torsional motion of the OH group of phenol between its equienergetical structures shown in Chart 4. The energy difference between this structure and the S o -state phenol molecule determines the torsional barrier V τ as equal to 13 after ZPVE at the B3LYP/6-311++G(d,p) computational level. The MP2/cc-pVTZ calculation recently performed yields 15 kJ mol −1 120 .…”

“…Contrary to Cl and Br, we obtain that the trans conformer of m-FC 6 H 4 OH is a little more stable than its cis conformer. The cis-trans differences in the geometrical (22), νC 1 C 6 (13), νC 1 C 2 (12), νCF (12) (14), βCOH (13), νC 5 C 6 (12), νC 1 C 2 (11), νC 4 C 5 (11), νC 3 C 4 (11) A νC 1 (21), τ 2 rg(11), γ CO(10) 831. 7 1 A β 2 rg (22), νCO (22), β 1 rg (15), νC 1 C 2 (13), νC 1 C 6 (13) 1279.…”