In this study, we present the results from the semiempirical molecular orbital calculations for the acylation step in the lipase-catalyzed ester hydrolysis. The results reveal that the lowest energy path for the formation of the tetrahedral intermediate is for the serine residue of the catalytic triad to attack the substrate, followed by coupling heavy atom movement and proton transfer. The cal...

Full geometry optimizations using the PM3, AMl, 3-21G*/HF and 6-31G*/HF levels of theory were conducted on the syn and anti conformations of cyclic 3’,5’-adenosine monophosphate (CAMP). Comparison of the anti crystal structures with the semiempirical and ab initio results revealed that the ab initio results agree well with the experimental results. The results of semiempirical calculations are ...

BexZn1 xTe thin films were grown on InP substrates by molecular beam epitaxy (MBE). Optical properties of the epilayers were studied using reflectance and photoluminescence (PL) measurements. An increase in the full width at half maximum of the emission line with the increase in BeTe content was observed and explained by the disorder-induced broadening. The temperature dependence of the band ga...

Ground movements during tunnel excavation are varied in magnitude and trend depending on several factors including the tunnel geometry, ground conditions, excavation methods, and support measures, etc. There exist several empirical and semi-empirical formulas available for predicting ground movements. These conventional methods, however, do not simultaneously take into consideration all the fac...

We have developed a computational approach that yields anharmonic vibrational couplings in molecular crystals. The approach is based on anharmonic vibrational potential-energy surface reconstruction starting from a normal-mode vibrational basis. The method was implemented for semiempirical Hamiltonians with periodic boundary conditions, with applications to crystalline naphthalene and pentaeryt...

— An attempt is made to provide a more rigorous basis for the description of solvent effects on chemical reactions by taking into account the various free energy contributions involved in the transfer of a substrate from the gas to the solution phase. It is shown that the solvent influence on various chemical and physical processes can be represented in a semiquantitative or even quantitative w...

Dielectronic recombination (DR) cross sections and rate coefficients are calculated for the isonuclear sequence FeZ+, with Z = 21, 20, 19, 18, 17, and 16, in which L-shell (2p-) excitations are involved during the initial capture. Most of the dominant transitions with ∆n = 0, using angular momentum average (AMA) approximation, are considered. It is found that the states 3pnd and 3dnd contribute...

A proposition for the nucleosidation mechanism of five-membered glycals promoted by N-iodo-succinimide (NIS), leading to 2 0-deoxy-2 0-iodo-b-nucleosides, is presented herein supported by semiempirical MO calculations. The proposed mechanism goes through the formation of multicomponent molecular intermediates that drastically diminish the total energy values when compared to charged intermediat...

A semiempirical shell model mass equation based on magic number Z = 126 and applicable to translead elements with N ≤ 126 is presented. For α-decay energies the equation is shown to have a high predictive power and an rms deviation from the data of about 100 keV. The rms deviations for masses and other mass differences are between about 200 and 300 keV. Recent progress in superheavy elements (S...

excited-sta,te charge distribution venting such a conformation. Extended Huckel calculations confirm this assumption. The potential energy curves for the rotation of the aldehyde group away from the plane of the phenyl ring for the ground state and the excited state of benzaldehyde arising from the carbonyl (n,n*) transition are shown in Figure 7. The calculated barrier to rotation is 0.22 eV f...