Average solvent electrostatic potential

An averaged solvent electrostatic potential, obtained by averaging over the solvent confignrations, is included in the solnte Hamiltonian and electric and energy properties are obtained. The method provides resnlts for the dipole moment and solnte-solvent interaction which agree with the experimental valnes and with the resnlts obtained by other workers (Mendoza et al., 1998). 

The ASEP/MD method, acronym for Averaged Solvent Electrostatic Potential from Molecular Dynamics, is a theoretical method addressed at the study of solvent effects that is half-way between continuum and quantum mechanics/molecular mechanics (QM/MM) methods. As in continuum or Langevin dipole methods, the solvent perturbation is introduced into the molecular Hamiltonian through a continuous distribution function, i.e. the method uses the mean field approximation (MFA). However, this distribution function is obtained from simulations, i.e., as in QM/MM methods, ASEP/MD combines quantum mechanics (QM) in the description of the solute with molecular dynamics (MD) calculations in the description of the solvent. 

Aguilar, Sanchez, Martin, Fdez. Galvan review the ASEP/MD method, acronym for Averaged Solvent Electrostatic Potential from Molecular Dynamics, showing how this method combines aspects of quantum mechanics/molecular mechanics (QM/MM) methods with aspects of continuum models. 

ASEP/MD, acronym for average solvent electrostatic potential obtained from molecular dynamics data, is a sequential QM/MM method that makes extensive use of the mean field approximation (MFA) [24], In solution, any static property A of the system must be calculated by averaging over the configurational space A defined by all the configurations thermally accessible to the system ... 

Solvent potential. The averaged solvent electrostatic field, , is important for inhomogeneous media, such as enzymes, membranes, miscelles and crystalline environments systems. Due to the existence of strong correlations, such a field does not cancel out. This factor becomes an important contribution to solvent effects at a microscopic level. In a study of non-rigid molecules in solution, Sese et al. [25] constructed a by using the solute-solvent atom-atom radial distribution function. Electrostatic interactions in three-dimensional solids were treated by Angyan and Silvi [26] in their self-consistent Madelung potential approach such a procedure can be traced back to a calculation of . An earlier application of the ISCRF theory to the study of proton mechanisms in crystals of hydronium perchlorate both [Pg.441]

A macroscopic treatment of solute-solvent electrostatic interactions is more justified, mainly because of the long range nature of electrostatic forces. As soon as one has been able to define the surface which separates the molecule from the continuum, one is able to use classical electrostatics to analyze the polarization of the solvent AAp, and of the averaged electrostatic potential in the cavity, which permits us to define the perturbation that the solute undergoes under the influence of the solvent. 

The first computations of ionization constants of residues in proteins for structures derived from molecular dynamics trajectories were described by Wendoloski and Matthew for tuna cytochrome c. In that study, conformers were generated using molecular dynamics simulations with a range of solvents, simulating macroscopic dielectric formalisms, and one solvent model that explicitly included solvent water molecules. The authors calculated individual pR values, overall titration curves, and electrostatic potential surfaces for average structures and structures along each simulation trajectory. However, the computational scheme for predicting electrostatic interactions in proteins used by Wendoloski and Matthew was not based on a FDPB model but on the modified Tanford-Kirkwood approach, which is not discussed in this chapter. 

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