J. Krechl - Academia.edu (original) (raw)
Papers by J. Krechl
ChemInform, 1989
ChemInform Abstract The title formates and acetates (I) are prepared and studied by ab initio 3-2... more ChemInform Abstract The title formates and acetates (I) are prepared and studied by ab initio 3-21G, 1H, and 13C NMR. Interaction between the two amidinium nitrogens and carboxylate oxygens is mediated by hydrogen bonds and alternation of charge distribution.
The Journal of Physical Chemistry, 1994
The potential energy surfaces for the addition of C02 to CH3NHCONH2 have been the subject of inte... more The potential energy surfaces for the addition of C02 to CH3NHCONH2 have been the subject of intensive research. Stationary points representing reactants, transition state, and products have been located and characterized using MNDO, MIND0/3, AM1, and PM3 semiempirical methods and ab initio 3-21G, 6-31G, and 6-31G* basis sets within Hartree-Fock (HF) procedures. The electron correlation has been estimated at MP2/3-21G, MP2/6-31G*//HF-6-31G*, and MP2/6-31G**//MP2/3-21G levels. The pathway connecting stationary points was traced by the IRC procedure. An analysis of the results shows that the addition is an asynchronous process, and the transition state structure can be described as a four-membered ring.
Acta Crystallographica Section C Crystal Structure Communications, 1987
Chemischer Informationsdienst, 1981
J. Chem. Soc., Perkin Trans. 2, 1995
... 106, 7206 Article ChemPort ; (f) JY Liang and WN Lipscomb, Biochemistry, 1987, 26, 5293 Artic... more ... 106, 7206 Article ChemPort ; (f) JY Liang and WN Lipscomb, Biochemistry, 1987, 26, 5293 Article ChemPort ; (g) SJ Formosinho and JJC Teixeira-Digs, J ... 14, DA Barstow, AR Clarke, WN Chia, D. Wigley, AF Sharman, JJ Holbrook, T. Atkinson and NP Minton, Gene, 1986, 46, 47 ...
J. Chem. Soc., Perkin Trans. 2, 1993
ABSTRACT
Synthesis, 1988
Reaction des composes du titre avec des derives maloniques: obtention de cyano-5 uraciles et thio... more Reaction des composes du titre avec des derives maloniques: obtention de cyano-5 uraciles et thio-2uraciles, d'ethoxycarbonyl-5 uraciles et d'amino-6 cyano-5 1H-pyrimidones-2 et -pyrimidinethiones-2
Journal of Molecular Structure: THEOCHEM, 1992
The unimolecular decomposition of the most simple amidine (formamidine) was examined by means of ... more The unimolecular decomposition of the most simple amidine (formamidine) was examined by means of ab initio molecular orbital calculations. The Hartree-Fock method in the linear combination of atomic orbit& approximation with the 4-31G basis set was used. A complete potential hypersurface was established and the stationary pointa representing the reactants (R), transition state (TS) and products (P) were located. An analysis of the results shows that formamidine decomposition is an asynchronous process. The TS can be described as a four-membered ring. Following these results we decided to investigate a more complex system (acetamidine) and to examine the relevance of Merent basis sets. For acetamidine decomposition the calculations were carried out using the 3-21G, 4-21G, 4-31G, 6-31G, 6-311G, 6-31G* and 6-31G-basis seta and the stationary points R, P and TS were located. It was found that the 4-31G basis set reproduces well the results obtained with more sophisticated calculations of energies and other quantum chemical indices. The structure of the TS was found to be relatively independent of the basis set used.
Tetrahedron Letters, 1976
Journal of the American Chemical Society, 1995
... J. And&,* V. Moliner, LR Domingo,? MT Picher,? ... in different methylotrophic an... more ... J. And&,* V. Moliner, LR Domingo,? MT Picher,? ... in different methylotrophic and autotrophic bacteria.' Salisbury et a1.* have isolated its redox cofactor from methylotrophic bacteria and based on its name, 2,7,9-tricarboxy-lH-pyrrolo[2,3-fl-quinoline-4,5-dione, the semisystematic ...
The Journal of Organic Chemistry, 1998
Journal of Inclusion Phenomena and Molecular Recognition in Chemistry, 1991
~H NMR spectroscopy was used to probe the formation of inclusion compounds of permethylated and p... more ~H NMR spectroscopy was used to probe the formation of inclusion compounds of permethylated and peracetylated fl-cyclodextrins as host molecules and a variety of electronically very different guest molecules. Complexation, obtained only in water, was estimated quantitatively by means of chemical shift/concentration curves of relevant protons, and the intermolecular forces involved are criticially discussed.
International Journal of Quantum Chemistry, 1991
Ab initio MO calculations have been carried out for the unimolecular decomposition of formamidine... more Ab initio MO calculations have been carried out for the unimolecular decomposition of formamidine. The Hartree–Fock method in LCAO approximation with the 4-31G basis set was used. The 4-31G potential hypersurface has been further studied. The stationary points (R, TS, and P) were localized. A reaction analysis by correlation of bond-order indices and localized molecular orbitals demonstrated that the decomposition is an asynchronous process. The TS can be described as four-membered ring.
International Journal of Quantum Chemistry, 1991
Electronic aspects of the catalytic mechanism of liver alcohol dehydrogenase (LADH) are studied w... more Electronic aspects of the catalytic mechanism of liver alcohol dehydrogenase (LADH) are studied with the help of ab initio analytical gradient SCFMO methods. Three points are considered: (i) role of the catalytic zinc; (ii) geometry and electronic structure of the transition state for the hydride transfer reaction; and (iii) factors affecting the energy gap for the hydride transfer step, namely, substrate binding to zinc, reaction field, and serine 48 effects on the potential energy profile. The coordination sphere of the catalytic zinc has been modeled with an ammonia molecule and two SH-groups; complexes with CHsO-, CHsOH, and CHzO have been studied; a (6,2,2,2,1/6,2,1/3,2) basis set has been used for Zn++; a (5,2,1,1/3,2) was used for oxygen, carbon, and sulfur; and a (3,l) was used for hydrogen atoms. The hydride step was studied with two model systems: pyridinium cation/l, 4-dihydropyridine coupled to the CH3O-/CH20 reaction, and cyclopropenyl cation/cyclopropene coupled to the CH30-/CH20 system. For the latter, the role of Ser48 has been studied at the supermolecule level. The calculation on the hydride transfer step has been done at a 4-3 1~ basis set level. The results obtained shed new light on the sources of catalytic activity of liver alcohol dehydrogenases.
International Journal of Quantum Chemistry, 1996
The influence of a hydroxyl group simulating Ser-48 in the hydride-transfer step characteristic o... more The influence of a hydroxyl group simulating Ser-48 in the hydride-transfer step characteristic of liver alcohol dehydrogenase is studied on the hydride-transfer reaction as modeled by a methanolate anion interacting with a cyclo propenyl cation. It is shown first that this is an adequate model by comparing it to the methanolate-pyrydinium cation model transition structure, (7s). The side-chain effect is modeled first by adding water and then with methanol located at the position that Ser-48 occupies in the enzyme; a supermolecule approach is used. It is found that (i) the normalized advance coordinate (NAC) for the exchanged hydrogen has an invariant value at the TS and the reactant, while for the product, the NAC depends upon the external perturbation introduced by the ancillary molecule (the TS is reactant-like); (ii) the products are strongly destabilized, so
International Journal of Quantum Chemistry, 1993
ABSTRACT
ChemInform, 1989
ChemInform Abstract The title formates and acetates (I) are prepared and studied by ab initio 3-2... more ChemInform Abstract The title formates and acetates (I) are prepared and studied by ab initio 3-21G, 1H, and 13C NMR. Interaction between the two amidinium nitrogens and carboxylate oxygens is mediated by hydrogen bonds and alternation of charge distribution.
The Journal of Physical Chemistry, 1994
The potential energy surfaces for the addition of C02 to CH3NHCONH2 have been the subject of inte... more The potential energy surfaces for the addition of C02 to CH3NHCONH2 have been the subject of intensive research. Stationary points representing reactants, transition state, and products have been located and characterized using MNDO, MIND0/3, AM1, and PM3 semiempirical methods and ab initio 3-21G, 6-31G, and 6-31G* basis sets within Hartree-Fock (HF) procedures. The electron correlation has been estimated at MP2/3-21G, MP2/6-31G*//HF-6-31G*, and MP2/6-31G**//MP2/3-21G levels. The pathway connecting stationary points was traced by the IRC procedure. An analysis of the results shows that the addition is an asynchronous process, and the transition state structure can be described as a four-membered ring.
Acta Crystallographica Section C Crystal Structure Communications, 1987
Chemischer Informationsdienst, 1981
J. Chem. Soc., Perkin Trans. 2, 1995
... 106, 7206 Article ChemPort ; (f) JY Liang and WN Lipscomb, Biochemistry, 1987, 26, 5293 Artic... more ... 106, 7206 Article ChemPort ; (f) JY Liang and WN Lipscomb, Biochemistry, 1987, 26, 5293 Article ChemPort ; (g) SJ Formosinho and JJC Teixeira-Digs, J ... 14, DA Barstow, AR Clarke, WN Chia, D. Wigley, AF Sharman, JJ Holbrook, T. Atkinson and NP Minton, Gene, 1986, 46, 47 ...
J. Chem. Soc., Perkin Trans. 2, 1993
ABSTRACT
Synthesis, 1988
Reaction des composes du titre avec des derives maloniques: obtention de cyano-5 uraciles et thio... more Reaction des composes du titre avec des derives maloniques: obtention de cyano-5 uraciles et thio-2uraciles, d'ethoxycarbonyl-5 uraciles et d'amino-6 cyano-5 1H-pyrimidones-2 et -pyrimidinethiones-2
Journal of Molecular Structure: THEOCHEM, 1992
The unimolecular decomposition of the most simple amidine (formamidine) was examined by means of ... more The unimolecular decomposition of the most simple amidine (formamidine) was examined by means of ab initio molecular orbital calculations. The Hartree-Fock method in the linear combination of atomic orbit& approximation with the 4-31G basis set was used. A complete potential hypersurface was established and the stationary pointa representing the reactants (R), transition state (TS) and products (P) were located. An analysis of the results shows that formamidine decomposition is an asynchronous process. The TS can be described as a four-membered ring. Following these results we decided to investigate a more complex system (acetamidine) and to examine the relevance of Merent basis sets. For acetamidine decomposition the calculations were carried out using the 3-21G, 4-21G, 4-31G, 6-31G, 6-311G, 6-31G* and 6-31G-basis seta and the stationary points R, P and TS were located. It was found that the 4-31G basis set reproduces well the results obtained with more sophisticated calculations of energies and other quantum chemical indices. The structure of the TS was found to be relatively independent of the basis set used.
Tetrahedron Letters, 1976
Journal of the American Chemical Society, 1995
... J. And&,* V. Moliner, LR Domingo,? MT Picher,? ... in different methylotrophic an... more ... J. And&,* V. Moliner, LR Domingo,? MT Picher,? ... in different methylotrophic and autotrophic bacteria.' Salisbury et a1.* have isolated its redox cofactor from methylotrophic bacteria and based on its name, 2,7,9-tricarboxy-lH-pyrrolo[2,3-fl-quinoline-4,5-dione, the semisystematic ...
The Journal of Organic Chemistry, 1998
Journal of Inclusion Phenomena and Molecular Recognition in Chemistry, 1991
~H NMR spectroscopy was used to probe the formation of inclusion compounds of permethylated and p... more ~H NMR spectroscopy was used to probe the formation of inclusion compounds of permethylated and peracetylated fl-cyclodextrins as host molecules and a variety of electronically very different guest molecules. Complexation, obtained only in water, was estimated quantitatively by means of chemical shift/concentration curves of relevant protons, and the intermolecular forces involved are criticially discussed.
International Journal of Quantum Chemistry, 1991
Ab initio MO calculations have been carried out for the unimolecular decomposition of formamidine... more Ab initio MO calculations have been carried out for the unimolecular decomposition of formamidine. The Hartree–Fock method in LCAO approximation with the 4-31G basis set was used. The 4-31G potential hypersurface has been further studied. The stationary points (R, TS, and P) were localized. A reaction analysis by correlation of bond-order indices and localized molecular orbitals demonstrated that the decomposition is an asynchronous process. The TS can be described as four-membered ring.
International Journal of Quantum Chemistry, 1991
Electronic aspects of the catalytic mechanism of liver alcohol dehydrogenase (LADH) are studied w... more Electronic aspects of the catalytic mechanism of liver alcohol dehydrogenase (LADH) are studied with the help of ab initio analytical gradient SCFMO methods. Three points are considered: (i) role of the catalytic zinc; (ii) geometry and electronic structure of the transition state for the hydride transfer reaction; and (iii) factors affecting the energy gap for the hydride transfer step, namely, substrate binding to zinc, reaction field, and serine 48 effects on the potential energy profile. The coordination sphere of the catalytic zinc has been modeled with an ammonia molecule and two SH-groups; complexes with CHsO-, CHsOH, and CHzO have been studied; a (6,2,2,2,1/6,2,1/3,2) basis set has been used for Zn++; a (5,2,1,1/3,2) was used for oxygen, carbon, and sulfur; and a (3,l) was used for hydrogen atoms. The hydride step was studied with two model systems: pyridinium cation/l, 4-dihydropyridine coupled to the CH3O-/CH20 reaction, and cyclopropenyl cation/cyclopropene coupled to the CH30-/CH20 system. For the latter, the role of Ser48 has been studied at the supermolecule level. The calculation on the hydride transfer step has been done at a 4-3 1~ basis set level. The results obtained shed new light on the sources of catalytic activity of liver alcohol dehydrogenases.
International Journal of Quantum Chemistry, 1996
The influence of a hydroxyl group simulating Ser-48 in the hydride-transfer step characteristic o... more The influence of a hydroxyl group simulating Ser-48 in the hydride-transfer step characteristic of liver alcohol dehydrogenase is studied on the hydride-transfer reaction as modeled by a methanolate anion interacting with a cyclo propenyl cation. It is shown first that this is an adequate model by comparing it to the methanolate-pyrydinium cation model transition structure, (7s). The side-chain effect is modeled first by adding water and then with methanol located at the position that Ser-48 occupies in the enzyme; a supermolecule approach is used. It is found that (i) the normalized advance coordinate (NAC) for the exchanged hydrogen has an invariant value at the TS and the reactant, while for the product, the NAC depends upon the external perturbation introduced by the ancillary molecule (the TS is reactant-like); (ii) the products are strongly destabilized, so
International Journal of Quantum Chemistry, 1993
ABSTRACT