Quantum mechanics/molecular mechanics (QM/MM) models are an appealing method for performing zeolite simulations. In QM/MM, a small cluster chosen to encompass the active center is described by QM, while the rest of the zeolite is described by MM. In the present study, we demonstrate that the charges and Lennard-Jones parameters on Si and O must be chosen properly for QM/MM calculations of adsor...

The bond-energy bond-order (BEBO) model of chemisorption allows an estimate to be made of the interaction energy between a gaseous specie and a solid surface as a function of either bond length or bond order, i.e., the length or order of either the gas-surface bond being formed or the bond of the gaseous molecule being broken. The relationship between bond energy and either bond length or bond ...

Silica molecular sieves that have the zeolite beta topology and contain framework Lewis acid centers (e.g., Zr-β, Sn-β) are useful catalysts in the Diels−Alder and dehydrative aromatization reactions between ethylene and various renewable furans for the production of biobased terephthalic acid precursors. Here, the main side products in the synthesis of methyl 4-(methoxymethyl)benzene carboxyla...

The effect of temperature on the activation energies of mitochondrial enzymes of the yeast Saccharomyces cerevisiae was examined. Non-linear Arrhenius plots with discontinuities in the temperature range 14-19 degrees C and 19-22 degrees C were observed for the respiratory enzymes and mitochondrial ATPase (adenosine triphosphatase) respectively. A straight-line Arrhenius plot was observed for th...

Stopped-flow circular dichroism and fluorescence spectroscopy are used to characterize the assembly of complexes consisting of plasmid DNA bound to the cationic lipids dimethyldioctadecylammonium bromide and 1, 2-dioleoyl- 3-trimethylammonium-propane and a series of polyamidoamine dendrimers. The kinetics of complexation determined from the stopped-flow circular dichroism measurements suggests ...

The reaction kinetics for drug blockade of postsynaptic channels at the mouse neuromuscular junction were studied. The activation energies associated with the onward and off-rate constants, from a sequential model, were measured for procaine, scopolamine, octanol, and heptanol, and from these the transition state thermodynamic parameters of free energy (AG$), enthalpy (AHI), and entropy (ASS) o...

The mechanism for the decomposition reaction of ethylamine, CH 3 CH 2 NH 2 , was investigated using high level ab initio and DFT calculations. Optimized geometries were fully optimized at MP2 and B3LYP levels of theory using 6-31G(d) and 6-31+G(d) basis sets. Single point energies were determined at G3MP2B3 and G3B3 levels of theory. Thermodynamics properties, activation energies, enthalpies an...

The adsorption energies and the activation energy barriers for a series of reactions catalyzed by gold surfaces and obtained theoretically through density functional theory (DFT) based calculations were considered to clarify the role of the low coordinated gold atoms and the role of doping in the catalytic activity of gold. The effect of the surface steps was introduced by comparison of the act...

Incident radiation has been reported to facilitate mercury release from soils. In this study the influence of light on mercury emissions from substrates amended with pure synthetic mercury species, and from naturally and anthropogenically mercury-enriched substrates were investigated using laboratory experiments and in situ flux measurements. Light-enhanced emissions were found to occur from su...

The gas-phase dissociation of perchloroethene (PCE), trichloroethene (TCE), and cis-dichloroethene (cis-DCE) on zerovalent iron Fe(110) was investigated using periodic density functional theory (DFT) with the generalized gradient approximation (GGA) and climbing image nudged elastic band method (CI-NEB). Activation energies and dechlorination rate constants for reductive beta-elimination of the...