The molecular geometry of orotic acid was fully optimized using the gradient minimization technique. The computed geometrical parameters at the B3LYP/6-311G** level correspond well to those determined experimentally by X-ray diffraction. The relative stability of both the syn and anti conformations was investigated at the B3LYP/6-311G** level, where the syn-form was shown to be slightly more st...

New bis-1,3,4-thiadiazoles 1–7 were obtained by the reaction of fumaric acid and N-(alkyl/aryl/cyclic)thiosemicarbazides in presence phosphorous oxychloride. The structures all compounds elucidated FT-IR, 1H NMR, 13C NMR elemental analysis. Antibacterial activity was studied for eight selected bacteria. Compounds 2–7 exhibited effect on Klebsiella pneumoniae. However, none Pseudomonas aeruginos...

Various mechanisms for the reversible formation of a covalent tetrahedral complex (TC) between papain and peptidyl aldehyde inhibitors were simulated by DFT calculations, applying the quantum mechanical/self consistent reaction field (virtual solvent) [QM/SCRF(VS)] approach. Only one mechanism correlates with the experimental kinetic data. The His-Cys catalytic diad is in an N/SH protonation st...

With current therapies becoming less efficacious due to increased drug resistance, new inhibitors of both bacterial and malarial targets are desperately needed. The recently discovered methylerythritol phosphate (MEP) pathway for isoprenoid synthesis provides novel targets for the development of such drugs. Particular attention has focused on the IspH protein, the final enzyme in the MEP pathwa...

Quinolinium cations and quinolinium betaines were investigated in the representative solvents water and acetonitrile at room temperature using stationary and time-resolved fluorescence spectroscopy (Single-Photon-Counting-method). Experimental results reveal that sulfoalkyland carboxyalkyl-quinolinium compounds display a strikingly different behavior in the two solvents. Furthermore, the fluore...

Investigation of tautomerism and transition states in a derivative of 1,3,4-oxadiazole (A, B, C and D) in the gas phase and in solution and in a micro hydrated environment with 1-3 water molecules was performed by calculations at the DFT-B3LYP/6-311++G(d,p) level of theory. The solvent effect is taken into account via the self-consistent reaction field (SCRF) method. The geometries of four poss...

This chapter reviews the theoretical background for continuum models of solvation, recent advances in their implementation, and illustrative examples of their use. Continuum models are the most efficient way to include condensed-phase effects into quantum mechanical calculations, and this is typically accomplished by the using self-consistent reaction field (SCRF) approach for the electrostatic...

The stabil ity of several base-pairs has been calcul ated in water mediu m usi ng self-consistent reac tion fie ld theory (SCRF) in the framework of Hart ree-Fock (HF) theory formalism. T he nomenclature used by Sponer eta/. (J phys Chem, I 00( 1996) 1965) have bee n used fo r all the basepai rs in ves tigated in th is work. The bindi ng energy is fou nd to increase fo r TAH, GT2, GC I , GA4, a...