J. B. Hasted

Bio: J. B. Hasted is an academic researcher. The author has contributed to research in topics: Volume (thermodynamics). The author has an hindex of 1, co-authored 1 publications receiving 79 citations.

Protein hydration in solution: Experimental observation by x-ray and neutron scattering

Abstract: The structure of the protein–solvent interface is the subject of controversy in theoretical studies and requires direct experimental characterization. Three proteins with known atomic resolution crystal structure (lysozyme, Escherichia coli thioredoxin reductase, and protein R1 of E. coli ribonucleotide reductase) were investigated in parallel by x-ray and neutron scattering in H2O and D2O solutions. The analysis of the protein–solvent interface is based on the significantly different contrasts for the protein and for the hydration shell. The results point to the existence of a first hydration shell with an average density ≈10% larger than that of the bulk solvent in the conditions studied. Comparisons with the results of other studies suggest that this may be a general property of aqueous interfaces.

Water structure of a hydrophobic protein at atomic resolution: Pentagon rings of water molecules in crystals of crambin.

Abstract: The water structure has been analyzed for a model of the protein crambin refined against 0.945-A x-ray diffraction data. Crystals contain 32% solvent by volume, and 77% of the solvent molecules have been located—i.e., 2 ethanol molecules and 64 water molecules with 10-14 alternate positions. Many water oxygen atoms found form chains between polar groups on the surface of the protein. However, a cluster of pentagonal arrays made up of 16 water molecules sits at a hydrophobic, intermolecular cleft and forms a cap around the methyl group of leucine-18. Several waters in the cluster are hydrogen-bonded directly to the protein. Additional closed circular arrays, which include both protein atoms and other water oxygen atoms, form next to the central cluster. This water array stretches in the b lattice direction between groups of three ionic side chains.

Tetra-n-butylammonium bromide-water (1/38).

Abstract: Tetra-n-butylammonium bromide forms the title semi-clathrate hydrate crystal, C16H36N+·Br−·38H2O, under atmospheric pressure. The cation and anion lie at sites with mm symmetry and seven water molecules lie at sites with m symmetry in space group Pmma. Br− anions construct a cage structure with the water molecules. Tetra-n-butyl­ammonium cations are disordered and are located at the centre of four cages, viz. two tetrakaideca­hedra and two pentakaidecahedra in ideal cage structures, while all the dodecahedral cages are empty.

Phase Behavior in Systems Containing Clathrate Hydrates: A Review

Abstract: Nature of Gas Hydrates 2 Structure of Gas Hydrates. 3 Phase Equilibria 6 Experimental Determinations of Phase Behavior«. 9 Phase Behavior in the Presence of Inhibitors 16 Thennodynaink Model 18 Calculation of^w 19 Calculation of&ua 24 Langmuir Constants 25 Molecular Simulations 33 Determination of Reference Properties 35 Equilibrium Calculations 38 Three Phase (VLfl, VIH, L^ff) Calculations Two Phase Calculations (VH) 39 Prediction of VL^fl Quadruple Points 46 Prediction of LJLJi Equilibrium (\\vuier-Liquid Hydrate Former-Hydrate) 46 Hydrate-Hydrate Equilibria 54 Six Phase Equilibria 58 Hydrate Azeotropes 58 Heat of Hydrate Formation 60 Conclusions and Summary 62 Nomenclature 63 References 66

The vibrational spectrum of the hydrated proton: Comparison of experiment, simulation, and normal mode analysis

Abstract: The vibrational properties of the hydrated proton and deuteron in bulk phase water and deuterated water are investigated spectroscopically and computationally. Mid-infrared spectra of aqueous acid solutions are measured by attenuated total reflectance-Fourier transform IR spectroscopy and compared with pure water and salt/counterion spectra to extract high-quality hydrated proton spectra at a series of concentrations. Multistate empirical valence bond simulations of the excess proton in bulk phase water are also performed, allowing the autocorrelation function of the time derivative of the dipole moment, and hence the power spectrum of the hydrated proton, to be evaluated. The experimental and theoretical spectra are found to be in very good agreement. Normal mode analysis of the bulk phase simulation data allows definitive assignment of the spectrum. The associated motions are found to be represented by both Eigen and Zundel forms of the hydrated proton.