SH Hydrogen Research Articles

Prediction of efficient promoter molecules of sH hydrogen hydrate: An ab initio study

The stabilizing ability of a series of promoter molecules on sH hydrogen hydrates was investigated by ab initio calculations and ab initio molecular dynamics simulations. The effect of the chemical activity of promoter molecules on the stability of the hydrogen hydrate was studied. The calculation results showed that the cohesive energy is an effective assessment indicator for the stability of the hydrate. Further, simulation results showed that the hydrogen hydrate can maintain its crystal structure for temperature ranging from 230 to 270 K, but its stability decreases with the increase of the temperature.

A method distinguishing between guest molecules that can form sI, sII, and sH hydrogen clathrates

A new method based on free energy calculations is proposed for discriminating between promoters that can form sI, sII, and sH hydrogen clathrates.

Free Energy Calculations for Identifying Efficient Promoter Molecules of Binary sH Hydrogen Clathrates

To determine the stabilizing effect of different promoter molecules on the clathrate, the Gibbs free energy of fully occupied binary sH hydrogen clathrates with secondary guest molecules in the large cages is calculated with Monte Carlo simulations. The small and medium cages of sH are occupied by one H2 guest molecule. Various promoter molecules enclathrated in the large cages are considered. Simulations are conducted in the pressure range of 250–1000 atm for temperatures ranging from 233 to 273 K. We investigate the effect of dipole moment and molecular size on the thermodynamic stability of sH hydrogen clathrate hydrate.

A new method for screening potential sII and sH hydrogen clathrate hydrate promoters with model potentials

A new predictive computational method for classifying clathrate hydrate promoter molecules is presented, based on the interaction energies between potential promoters and the water networks of sII and sH clathrates. The motivation for this work is identifying promoters for storing hydrogen compactly in clathrate hydrates. As a first step towards achieving this goal, we have developed a general method aimed at distinguishing between molecules that form sII clathrate hydrates and molecules that can-together with a weakly interacting help gas-form sH clathrate hydrates. The new computational method calculates differences in estimated formation energies of the sII and the sH clathrate hydrate. Model interaction potentials have been used, including the electrostatic interactions with newly calculated partial charges for all the considered potential promoter molecules. The methodology can discriminate between the clathrate structure types (sII or sH) formed by each potential promoter with good selectivity, i.e., better than achieved with a simple van der Waals diameter criterion.

Phase Equilibrium Measurements of Structure sH Hydrogen Clathrate Hydrates with Various Promoters

The potential of clathrate hydrates for hydrogen storage has already been demonstrated in various publications. Today, a major scientific and technological challenge would be the finding of a storage material that allows for storage of larger quantities of hydrogen, as required for new energy applications such as, for instance, in the transport sector and fulfilling the goals set by some energy agencies which require the achievement of storage capacities up to a mass fraction of 6 % of hydrogen and with an environmentally clean and safe method by the end of 2010. If it would be possible to store hydrogen in structure sH clathrate hydrate (sH), this goal possibly could be achieved. Our previous work demonstrated for the first time the possibility to crystallize hydrogen clathrate hydrate in structure sH with 1,1-dimethylcyclohexane, methyl tert-butyl ether (MTBE), and methylcyclohexane as promoters. In this work, phase equilibrium data (p, T data) are reported for hydrogen clathrate hydrate systems with liquid hydrocarbon promoters, all of them forming the structure sH. Experiments were carried out at pressures up to 100.0 MPa.

Spectra, ionization constants, and rates of oxidation of 1,4-dimercaptobenzene and properties of the p-mercaptophenylthiyl and p-benzodithiyl anion radicals

In basic solution, p-dimercaptobenzene, which is found to have pK a 's of 6.0 and 7.7, is rapidly oxidied by azide radical (k=7.4×10 9 M -1 s -1 ) to p-benzodithiyl radical anion, the sulfur analog of p-benzosemiquinone radical anion. This radical has very strong absorption bands at 390 and ∼700 nm. In acidic solutions, CO 2 .- abstracts a SH hydrogen atom (k=3.1×10 9 M -1 s -1 ) to form the p-mercaptophenylthiyl radical, which has absorption maxima at 350 and 585 nm and a pk a , of 2.7

Structural studies of viruses by laser Raman spectroscopy. Part XXXVI. Cysteine conformation and sulfhydryl interactions in proteins and viruses. 2. Normal coordinate analysis of the cysteine side chain in model compounds

We report vibrational normal mode analyses of cysteine and several model mercaptans containing the -CHRCH 2 SH group (R=H or CH 3 ). The results provide a basis for assigning observed Raman frequencies to specific conformers of the cysteinyl C α -C β -S-H side chain and for assessing SH hydrogen bonding with appropriate donor and acceptor groups

Chemical probing of the light-induced interaction between rhodopsin and G-protein. Near-infrared light-scattering and sulfhydryl modifications.

Near-infrared light scattering and gel electrophoresis were used to monitor the interaction between rhodopsin and G-protein at photoreceptor disc membranes. It is found that substitution of one SH hydrogen at the G alpha-subunit by N-ethylmaleimide or thionitrobenzoate still allows dark binding of the G-unit to the membrane but blocks its light binding to rhodopsin. Repair of the modification restores the interaction of the proteins. Evidence is provided that substitution by the less bulky cyanide is also able to remove the hindrance to light binding. The rhodopsin-G interaction is reduced in proportion to bound N-ethylmaleimide, and the interaction kinetics remain constant over the measurable range. GTP/GDP exchange at the G-protein after interaction with rhodopsin does not reduce the accessibility of the relevant SH group. In contrast to the effect of G-protein modification, even exhaustive modification of rhodopsin has no effect on the dark and light binding of G-protein.