The importance of including polarization functions in the basis set of ab initio MO calculations has received a good deal of attention during the last few years [1—8]. However, little work has been reported on the influence of the inclusion of polarization functions in the basis set of semiempirical methods. The only papers dealing with semiempirical methods that the authors are aware of are, o...

The suitability of ab initio, semiempirical and density functional methods as sources of stretching and bending parameters has been explored using the PAPQMD (Program for Approximate Parametrization from Quantum Mechanical Data) strategy. Results show that semiempirical methods provide parameters comparable to those compiled on empirical force fields. In this respect the AMI method seems to be ...

We have examined the performance of semiempirical quantum mechanical methods in solving the problem of accurately predicting protein-ligand binding energies and geometries. Firstly, AM1 and PM3 geometries and binding enthalpies between small molecules that simulate typical ligand-protein interactions were compared with high level quantum mechanical techniques that include electronic correlation...

New quaternary 3-phthalimidopropylammonium conjugates of steroids were obtained by reaction of sterols (ergosterol, cholesterol, cholestanol) and bile acids (lithocholic, deoxycholic, cholic) with bromoacetic acid bromide to give sterol 3β-bromoacetates and bile acid 3α-bromoacetates, respectively. These intermediates were subjected to nuclephilic substitution with N,N-dimethyl-3-phthalimidopro...

The present work outlines a new method for treatment of charge-dependent polarizability in semiempirical quantum models for use in combined quantum-mechanical/molecular mechanical simulations of biological reactions. The method addresses a major shortcoming in the performance of conventional semiempirical models for these simulations that is tied to the use of a localized minimal atomic-orbital...

The calibration methods for in-situ gamma spectrometry systems used CIEMAT include semiempirical approaches using point sources, pure mathematical calibrations using the ISOCS software and a stripping method developed at CIEMAT. The two first procedures give information about the activity concentration in the soil, and the third method provides distributions of dosimetric quantities as a functi...