Search results for "solvation"

Existence of metastable intermediate lysozyme conformation highlights the role of alcohols in altering protein stability.

2011

Alcohols have a manifold effect on the conformational and thermodynamic stability of native proteins. Here, we study the effect of moderate concentrations of trifluoroethanol (TFE) on the thermal stability of hen egg-white lysozyme (HEWL), by far-UV circular dichroism and by steady-state and time-resolved photoluminescence of intrinsic tryptophans. Our results highlight that TFE affects lysozyme stability by preferential solvation of the protein molecule. Furthermore, we discovered the existence at 20% TFE of an equilibrium partially folded state of lysozyme, intermediate between the native and the unfolded state. A three-state model is therefore used to interpolate the thermal denaturation…

Correction of cavity-induced errors in polarization charges of continuum solvation models

1998

Structure of diblock copolymers in supercritical carbon dioxide and critical micellization pressure

1999

This paper reports a small angle neutron scattering investigation of micelle formation by fluorocarbon-hydrocarbon block copolymers in supercritical ${\mathrm{CO}}_{2}{(\mathrm{s}\mathrm{c}\ensuremath{-}\mathrm{C}\mathrm{O}}_{2})$ at 65 \ifmmode^\circ\else\textdegree\fi{}C. A sharp unimer-micelle transition is obtained due to the tuning of the solvating ability of ${\mathrm{s}\mathrm{c}\ensuremath{-}\mathrm{C}\mathrm{O}}_{2}$ by profiling pressure, so that the block copolymer, in a semidilute solution, finds ${\mathrm{s}\mathrm{c}\ensuremath{-}\mathrm{C}\mathrm{O}}_{2}$ a good solvent at high pressure and a poor solvent at low pressure. At high pressure the copolymer is in a monomeric state…

Nature of the non-exponential primary relaxation in structural glass-formers probed by dynamically selective experiments

1998

Several experimental methods feature the potential to distinguish between slow and fast contributions to the non-exponential, ensemble averaged primary response in glass-forming materials. Some of these techniques are based on the selection of subensembles using multi-dimensional nuclear magnetic resonance, optical bleaching, and non-resonant spectral hole burning. Others, such as the time-dependent solvation spectroscopy, measure microscopic responses induced by local perturbations. Using several of these methods it could be demonstrated for various glass-forming materials that the non-exponential relaxation results from a superposition of dynamically distinguishable entities. The experime…

A density functional theory evaluation of hydrophobic solvation: Ne, Ar and Kr in a 50-water cluster – Implications for the hydrophobic effect

2012

The physical explanation for the hydrophobic effect has been the subject of disagreement. Physical organic chemists tend to use a explanation related to pressure, while many biochemists prefer an explanation that involves decreased entropy of the aqueous solvent. We present DFT calculations at the B3LYP/6-31G(d,p) and X3LYP/6-31G(d,p) levels on the solvation of three noble gases (Ne, Ar, and Kr) in clusters of 50 waters. Vibrational analyses show no substantial decreases in the vibrational entropies of the waters in any of the three clusters. The observed positive free energies of transfer from the gas phase or from nonpolar solvents to water appear to be due to the work needed to make a su…

A Microscopic Interpretation of Pump–Probe Vibrational Spectroscopy Using Ab Initio Molecular Dynamics

2018

What happens when extra vibrational energy is added to water? Using nonequilibrium molecular dynamics simulations, also including the full electronic structure, and novel descriptors, based on projected vibrational density of states, we are able to follow the flow of excess vibrational energy from the excited stretching and bending modes. We find that the energy relaxation, mostly mediated by a stretching-stretching coupling in the first solvation shell, is highly heterogeneous and strongly depends on the local environment, where a strong hydrogen bond network can transport energy with a time scale of 200 fs, whereas a weaker network can slow down the transport by a factor 2-3.

Bis[3-methyl-5-(pyridin-2-yl)-1H-pyrazol-4-yl] selenide methanol hemisolvate

2014

The asymmetric unit of the title compound, C18H16N6Se·0.5CH3OH, contains two independent molecules of bis[3-methyl-5-(pyridin-2-yl)-1H-pyrazol-4-yl] selenide with similar C—Se—C bond angles [99.30 (14) and 98.26 (13)°], and a methanol molecule of solvation. In one molecule, the dihedral angles between pyrazole and neighbouring pyridine rings are 18.3 (2) and 15.8 (2)°, and the corresponding angles in the other molecule are 13.5 (2) and 8.3 (2)°. In the crystal, the selenide and solvent molecules are linked by classical O—H...N and N—H...N hydrogen bonds, as well as by weak C—H...O and C—H...π interactions, forming a three-dimensional supramolecular architecture.

Solubility and solvation features of native cyclodextrins in 1-ethyl-3-methylimidazolium acetate

2022

The comprehension of the mechanism entailing efficient solvation of cyclodextrins (CD) by green solvents is of great relevance to boost environmentally sustainable usages of smart supramolecular systems. Here, 1-ethyl-3- methylimidazolium acetate, an ecofriendly ionic liquid (IL), is considered as an excellent solvent for native CDs. This IL efficiently dissolves up to 40 wt.% β- and γ-CD already at ambient temperature and X-ray scattering indicates that CDs do not tend to detrimental flocculation under these drastic concentration conditions. Simu- lation techniques reveal the intimate mechanism of CD solvation by the ionic species: while the strong hydrogen bonding acceptor acetate anion i…

The electronic spectra of 2-(2′-hydroxybenzoyl)pyrrole and 2-(2′-methoxybenzoyl)pyrrole: a theoretical study

2005

The gas-phase electronic spectra of 2-(2 0 -hydroxybenzoyl)pyrrole and 2-(2 0 -methoxybenzoyl)pyrrole have been determined using multiconfigurational perturbation theory (CASPT2). Solvatochromic spectral shifts for these molecules have been measured in cyclohexane and methanol and the electrostatic components of these shifts have been estimated using the vertical electrostatic model (VEM 4.2) developed for the configuration interaction with single excitations model implemented with the intermediate neglect of differential overlap Hamiltonian (CIS/INDO/ S2). Comparison between theory and experiment and an interpretation of the main spectral differences between the two substituted pyrroles an…

Three-dimensional solvation structure of ethanol on carbonate minerals

2020

Calcite and magnesite are important mineral constituents of the earth’s crust. In aqueous environments, these carbonates typically expose their most stable cleavage plane, the (10.4) surface. It is known that these surfaces interact with a large variety of organic molecules, which can result in surface restructuring. This process is decisive for the formation of biominerals. With the development of 3D atomic force microscopy (AFM) it is now possible to image solid–liquid interfaces with unprecedented molecular resolution. However, the majority of 3D AFM studies have been focused on the arrangement of water at carbonate surfaces. Here, we present an analysis of the assembly of ethanol – an o…