Free energy of solvation of a spherical ion in a force-field water is studied by numerical simulations. The focus is on the linear solvation susceptibility connecting the linear response solvation free energy to the squared ion charge. Spherical hard-sphere solutes, hard-sphere ions, and Kihara solutes (Lennard-Jones modified hard-sphere core) are studied here. The scaling of the solvation susc...

Solvation forces are crucial determinants in the equilibrium between the folded and unfolded state of proteins. Particularly interesting are the solvent forces of denaturing solvent mixtures on folded and misfolded states of proteins involved in neurodegeneration. The C-terminal globular domain of the ovine prion protein (1UW3) and its analogue H2H3 in the α-rich and β-rich conformation were us...

Using extensive equilibrium molecular dynamics simulations we determine the dielectric spectra of aqueous solutions of NaF, NaCl, NaBr, and NaI. The ion-specific and concentration-dependent shifts of the static dielectric constants and the dielectric relaxation times match experimental results very well, which serves as a validation of the classical and non-polarizable ionic force fields used. ...

We have studied the effect of weak solute-solvent attractions on the solvation of nonpolar molecules in water at ambient conditions using an extension and improved parameterization of the theory of solvation due to Lum, Chandler, and Weeks [J. Phys. Chem. B 1999, 103, 4570]. With a reasonable strength of alkanewater interactions, an accurate prediction of the alkane-water interfacial tension is...

Thermodynamic data are often used to calibrate or test amomic-level (AL) force fields for molecular dynamics (MD) simulations. In contrast, the majority of coarse-grained (CG) force fields do not rely extensively on thermodynamic quantities. Recently, a CG force field for lipids, hydrocarbons, ions, and water, in which approximately four non-hydrogen atoms are mapped onto one interaction site, ...

Classical force fields for molecular simulations of aqueous electrolytes are still controversial. We study alkali and halide ions at the air/water interface using novel non-polarizable force fields that were optimized based on bulk thermodynamics. In qualitative agreement with polarizable force-field simulations, ion repulsion from the interface decreases with increasing ion size. Iodide is eve...

We analyze the equilibrium response of random heteropolymers to mechanical deformation. In contrast to homopolymer response, the stress-induced transformation of a heteropolymer from globule to coil need not be sharp. For chain lengths relevant to biological macromolecules, intermediate necklace-like structures dominate over a range of applied force. Stability of these conformations is primaril...

We analyze the dynamics of an atomic force microscopy AFM cantilever oscillating in liquid at subnanometer amplitude in the presence of tip-sample interaction. We present AFM measurements of oscillatory solvation forces for octamethylcyclotetrasiloxane on highly oriented pyrolitic graphite and compare them to a harmonic oscillator model that incorporates the effect of the finite driving force f...

We optimize force fields for H3O(+) and OH(-) that reproduce the experimental solvation free energies and the activities of H3O(+) Cl(-) and Na(+) OH(-) solutions up to concentrations of 1.5 mol/l. The force fields are optimized with respect to the partial charge on the hydrogen atoms and the Lennard-Jones parameters of the oxygen atoms. Remarkably, the partial charge on the hydrogen atom of th...

We present a mechanism for the stabilization of colloids in liquid mixtures without use of surfactants or polymers. When a suitable salt is added to a solvent mixture, the coupling of the colloid's surface chemistry and the preferential solvation of ions leads to a repulsive force between colloids that can overcome van der Waals attraction. This repulsive force is substantial in a large range o...