The results of MNDO, AM1 and PM3 semi-empirical calculations and HF/6-31G*, MP/6-31G*, MP2/6-311+G**, and B3LYP/6-311G** and QCISD/6-31G* ab initio methods for angle strain and conjugation effects in twist-boat, boat, and half-chair geometries of (Z,Z,Z)-cycloocta-1,3,5-triene indicate that all methods, except PM3, predict wrong ordering of the conformations.

The article presents extended computer investigations of various sulfate derivatives of riboflavin. A number of physicochemical parameters such as total energy, binding energy and formation heat were calculated via semi-empirical methods AM1 and PM3 for the different derivatives of riboflavin. Their analysis made it possible to determine the sequence of formation of sulfate derivatives--esterif...

The idea of similarity index was extended to the investigation of the effect of spin recoupling in chemical reactions. The approach was applied at the semiempirical AM1 level to a series of selected pericyclic reactions involving model examples of electrocyclic reactions, cycloadditions and valence isomerizations. Both allowed and forbidden reaction mechanisms were analyzed in each case with th...

In this paper we investigate (using AM1 semi-empirical as well as HF methods at the STO-3G, 3-21G, 6-31G, 6-31G* and 6-31+G** level) the conformations, geometrical parameters, Mulliken charges, and solvation effects of the triphosphate form of AZT (AZTTP), as well as the thymidine nucleotide (dTTP) structure. Our calculated geometrical parameters and Mulliken charges, with and without solvation...

A number of physicochemical parameters were calculated via semi-empirical methods AM1 and PM3 for the molecule of riboflavin at various protonation states. Their analysis made it possible to determine the acidicity of appropriate groups of this compound. The sequence of protons dissociation and accepting by the neutral molecule of riboflavin was determined. This methodology may be used to study...

2014 Photovoltaic devices have been obtained by a direct polymerization of undoped (or p-type doped) thin film (CH)x layer onto a polycrystalline cadmium sulfide film. The morphology of the contact is observed by S.E.M. microscopy. The electrical characteristics of this device are studied in the dark or under illumination. The main result, at AM1, 100 mW/cm2 with doped (CH)x correspond to 0.5 p...

oniom calculation is carried out to estimate the acidity of five aliphatic alcohols before and after adsorbing on the tip of (8,0) single-walled carbon nanotube. the oniom method is performed using a combination of density functional theory and am1 semiemperical method for alcohols and their corresponding conjugated bases. deprotonation gibbs free energies of alcohols are calculated and compare...

BACKGROUND After renal transplantation, patients with insufficient graft function may require phosphate binders. It is still unknown if sevelamer, a new calcium-free phosphate binder, interferes with the uptake of immunosuppressants. We studied its effects on the pharmacokinetics of cyclosporin A (CsA) and mycophenolate mofetil. METHODS We examined 10 adults and eight children with stable ren...

Soluble epoxide hydrolase (sEH) is an enzyme involved in drug metabolism that catalyzes the hydrolysis of epoxides to form their corresponding diols. sEH has a broad substrate range and shows high regio- and enantioselectivity for nucleophilic ring opening by Asp333. Epoxide hydrolases therefore have potential synthetic applications. We have used combined quantum mechanics/molecular mechanics (...

We present a new set of geometry-based functional forms for parametrizing effective Coulomb radii and atomic surface tensions of organic solutes in water. In particular, the radii and surface tensions depend in some cases on distances to nearby atoms. Combining the surface tensions with electrostatic effects included in a Fock operator by the generalized Born model enables one to calculate free...