A theory is presented which allows us to quantitatively calculate the excess surface tension of acid solutions. The H(+), in the form of hydronium ion, is found to be strongly adsorbed to the solution-air interface. To account for the electrostatic potential difference measured experimentally, it is necessary to assume that the hydronium ion is oriented with its hydrogens pointing into the bulk...

PCE (protein continuum electrostatics) is an online service for protein electrostatic computations presently based on the MEAD (macroscopic electrostatics with atomic detail) package initially developed by D. Bashford [(2004) Front Biosci., 9, 1082-1099]. This computer method uses a macroscopic electrostatic model for the calculation of protein electrostatic properties, such as pK(a) values of ...

A qualitatively new understanding of the nature of ions at the liquid water surface is emerging. Traditionally, the characterization of liquid surfaces has been limited to macroscopic experimental techniques such as surface tension and electrostatic potential measurements, wherein the microscopic picture then has to be inferred by applying theoretical models. Because the surface tension of elec...

The central event in the pathogenesis of prion protein (PrP) is a profound conformational change from its α-helical (PrP(C)) to its β-sheet-rich isoform (PrP(Sc)). Many single amino acid mutations of PrP are associated with familial prion diseases, such as D202N, E211Q, and Q217R mutations located at the third native α-helix of human PrP. In order to explore the underlying structural and dynami...

Mineralization of fibrillar collagen with biomimetic process-directing agents has enabled scientists to gain insight into the potential mechanisms involved in intrafibrillar mineralization. Here, by using polycation- and polyanion-directed intrafibrillar mineralization, we challenge the popular paradigm that electrostatic attraction is solely responsible for polyelectrolyte-directed intrafibril...

We construct a mean-field variational model to study how the dependence of dielectric coefficient (i.e., relative permittivity) on local ionic concentrations affects the electrostatic interaction in an ionic solution near a charged surface. The electrostatic free-energy functional of ionic concentrations, which is the key object in our model, consists mainly of the electrostatic potential energ...

The excited state intramolecular proton transfer (ESIPT) in 1-(trifluoroacetylamino)naphthaquinone (TFNQ) has been investigated using the CASSCF and CASPT2 computational approaches with the 6-31G(d) basis set. The structures and relative energies of critical points along the proton transfer reaction coordinate were optimized and the associated spectroscopic and electrostatic properties obtained...

The unreported brucinium benzilate (BBA) crystal and Hirshfeld surface analysis indicated the influence of intramolecular hydrogen bonding network on structure. Protonation occurs at tertiary nitrogen as it is most basic site. protonated N-H+ proton was observed 7.08 ppm carbon COO- 178.41 ppm. Molecular electrostatic potential (MEP) studies showed electron-rich electron-deficient sites in mole...

The K72A/K73H/K79A variant of cytochrome c undergoes a reversible change from a His/Met to a His/His axial heme ligation upon urea-induced unfolding slightly below neutral pH. The unfolded form displays a dramatically lower reduction potential than the folded species along with a pseudo-peroxidase activity. We have studied electrochemically the effects of urea-induced unfolding on the protein e...

Surface second harmonic generation has been used to study the adsorption of alkyl phenols and anilines and their respective ions to the air/water interface. The free energies of adsorption of the neutral molecules were obtained using a simple Langmuir model. The quantitative effects of the opposing hydrophobic and solvations forces on molecular adsorption were investigated by varying the chain ...