scholarly journals Examination of the Reduced Affinity of the Thymidylate Synthase G52S Mutation for FdUMP by Ab Initio and Semi-empirical Studies

2001 ◽  
Vol 7 (3) ◽  
pp. 200-204 ◽  
Author(s):  
Anne-Marie Sapse ◽  
Gina M. Capiaux ◽  
Joseph R. Bertino
Keyword(s):  
Ab Initio ◽  
Thymidylate Synthase ◽  
Empirical Studies ◽  
Semi Empirical

Relation between Magnetic, Spectroscopic and Structural Properties of Binuclear Copper(II) Complexes of Pentadentate Schiff-base Ligand, Semi-empirical and ab-initio Calculations

2003 ◽  
Vol 58 (5-6) ◽  
pp. 363-372 ◽  
Author(s):  
Y. Elerman ◽  
H. Kara ◽  
A. Elmali
Keyword(s):  
Ab Initio ◽  
Coupling Constants ◽  
Antiferromagnetic Coupling ◽  
X Ray Diffraction ◽  
Hartree Fock ◽  
Ligand Orbital ◽  
Rhf Calculations ◽  
The Difference ◽  
Semi Empirical

The synthesis and characterization of [Cu2(L1)(3,5 prz)] (L1=1,3-Bis(2-hydroxy-3,5-chlorosalicylideneamino) propan-2-ol) 1 and of [Cu2(L2)(3,5 prz)] (L2=1,3-Bis(2-hydroxy-bromosalicylideneamino) propan-2-ol) 2 are reported. The compounds were studied by elemental analysis, infrared and electronic spectra. The structure of the Cu2(L1)(3,5 prz)] complex was determined by x-ray diffraction. The magnetochemical characteristics of these compounds were determined by temperaturedependent magnetic susceptibility measurements, revealing their antiferromagnetic coupling. The superexchange coupling constants are 210 cm−1 for 1 and 440 cm−1 for 2. The difference in the magnitude of the coupling constants was explained by the metal-ligand orbital overlaps and confirmed by ab-initio restricted Hartree-Fock (RHF) calculations. In order to determine the nature of the frontier orbitals, Extended Hückel Molecular Orbital (EHMO) calculations are also reported.

Relativistic AB Initio calculations of the properties of ionic solids

1986 ◽  
Vol 320 (1553) ◽  
pp. 107-158 ◽  
Keyword(s):  
Ab Initio ◽  
Short Range ◽  
Correlation Energy ◽  
Electron Gas ◽  
Empirical Method ◽  
Coulombic Interactions ◽  
Ionic Solids ◽  
Electron Correlation Energy ◽  
Crystal Properties ◽  
Semi Empirical

Relativistic ab initio calculations of inter-ionic potential energies are used to develop a reliable non-empirical method for predicting the properties of ionic solids containing the heaviest ions. A physically realistic method for describing the non-negligible differences between free and in-crystal ion wavefunctions is described. Functions are presented for describing the partial quenching, arising from ion wavefunction overlap, of the standard long-range form of the inter-ionic dispersive attractions. These attractions are shown to be distinct from the contributions to the inter-ionic potentials that arise from that portion of the electron correlation energy which is nonzero solely because of overlap of the ion wavefunctions. The results presented for NaCl, MgO and the fluorides of Li, Na, Ag and Pb show that these modifications overcome the deficiencies of previous calculations. Ab initio predictions of the closest cation-cation and anion-anion short-range interactions, which are not available from semi-empirical fits to experimental data, are presented. The non-point coulombic interactions between pairs of anions, derived by adding the dispersive attractions to the short-range interactions, are compared with previous semi-empirical and approximate ab initio results. The uncorrelated short-range inter-ionic potentials computed exactly are compared with those predicted from electron-gas theory. The use of the electron-gas approximation to describe any of these potentials degrades the quality of the predicted crystal properties.

The phonons of the Al surfaces: comparison between semi-empirical and ab initio calculations

1992 ◽  
Vol 269-270 ◽  
pp. 146-151 ◽  
Author(s):  
A. Franchini ◽  
V. Bortolani ◽  
G. Santoro ◽  
J.A. Gaspar ◽  
A.G. Eguiluz
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Semi Empirical
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