Showing papers by "Enrico Clementi published in 1979"
TL;DR: In this paper, the atom pair potentials for Na+/ionophore complexes with a thioether, ethers, and amides were obtained from ab initio SCF-LCAO-MO calculations for model complexes of Na+ with various ionophores, and the analysis of the inter-and intramolecular atom-pair interactions indicated that Na+ binding is primarily due to the polarization of the model compound in the field of of the sodium ion.
Abstract: Atom pair potentials are obtained from ab initio SCF‐LCAO‐MO calculations for model complexes of Na+ with a thioether, ethers, and amides. The SCF‐LCAO‐MO interaction energies for 600 complexes of Na+ with such ionophores were fitted with a simple analytical potential. The analysis of the inter‐ and intramolecular atom‐pair interactions indicates that Na+/ionophore binding is primarily due to the polarization of the model compound in the field of of the sodium ion.
33 citations
TL;DR: The formation of H2C03 from H,O and COz in the gas phase requires a substantial activation energy and is a thernlodynanlically unfavourable process; in aqueous solution the activation energy is lower, but still high enough to constitute in principle a rate-limiting step in biochemical processes.
31 citations
TL;DR: It is shown that, at least for certain combinations of the internal rotation angles, the choice of the starting geometry for the sugarphosphate–sugar molecule (bond lengths and valence angles) strongly affects the value of the computed energy.
Abstract: In preceding papers the energies associated with the internal rotations in the sugar–phosphate–sugar complex were described with an analytical potential consisting of a Lennard-Jones 6–12 term and an intrinsic torsional term and representing the best fit to a large number of energies computed with a quantum mechanical ab initio technique. The complex considered there (of 37 atoms and with the chemical formula C10H18O8P) is repesentative of deoxyribonucleic acids. In this paper we apply our potential to evaluating the intramolecular energies of the 39-atom complex C10H18O10P, representative of the ribonucleic acids. The potential energies for the internal rotations (considered independent from one another) and the energy maps for rotations about consecutive bonds of the backbone chain are critically compared, both with those obtained for the deoxy system and with those obtained from different theoretical approaches as available from literature. It is shown that, at least for certain combinations of the internal rotation angles, the choice of the starting geometry for the sugarphosphate–sugar molecule (bond lengths and valence angles) strongly affects the value of the computed energy. If a proper geometry is used, very low energies are predicted by our potential in correspondence of the sets of torsional angles found in various RNAs by x-ray crystallography.
4 citations