Showing papers by "Kwang S. Kim published in 1996"

The nature of a wet electron.

Abstract: A comprehensive state-of-the-art ab initio study is performed on the wet electron---an electron interacting with a small cluster of water molecules---in the water hexamer system. Predictions include two previously unknown distinctive geometries which bind the excess electron as internal and external states, photoemission ionization energies in agreement with experiment, identification of generic electrophilic sites involving dangling hydrogen atoms, and the tendency of all hydrogen atoms to be saturated in hydrogen bonding or in interaction with the excess electron. An emerging insight is the capability of electrophilic sites to be actuators of electron transport pathways in biomolecular systems.

Ab initio study of the structures, energetics, and spectra of Aquazinc(II)

Abstract: By using extensive ab initio calculations including electron correlation, we have studied the structures, thermodynamic quantities, and spectra of hydrated zinc ions [Zn(H2O)n2+ (n = 1−6)]. Various conformers for n = n1 + n2 (where n1 and n2 are the numbers of water molecules in the first and second hydration shells, respectively) were investigated along with their thermodynamic quantities. The entropy effect was found to be important for the stabilities. At 0 K, the most stable structures for n = 5 and 6 are 5 + 0 and 6 + 0, respectively. However, at room temperature, both 4 + 1 and 5 + 0 seem to be almost equally populated in the case of n = 5, while 6 + 0 is the most populated in the case of n = 6. The predicted successive binding energies for the addition of each water molecule to the zinc ion are reported. The vibrational frequency shifts, depending on the number of water molecules, were investigated along with the frequency characteristics, depending on the presence/absence of outer-shell water mole...

Ab Initio Conformational Study of 1,2:4,5-Di-O-isopropylidene-myo-inositol

Abstract: Inositol phosphate derivatives play key roles in intracellular signal transduction. The X-ray structure of 1,2:4,5-diisopropylidene-myo-inositol is different from the conformer predicted by NMR and IR spectra. Therefore, we performed ab initio conformational study of the molecule, as a preliminary study before investigating the regioselectivity displayed by the myo-inositol toward electrophiles. The relative stabilities of four possible conformers of the molecule were investigated at various levels of ab initio theory: Hartree−Fock (HF) theory, Moller−Plesset second-order perturbation (MP2) theory, density functional theory (DFT), and self-consistent reaction field (SCRF) theory. Various basis sets were also tested. All calculations gave a consistent result which shows strong intramolecular hydrogen bonding interaction in an isolated system such as gas phase or solution. This is in agreement with NMR experiment. The frequency splitting between two OH vibrational frequencies due to the difference in the s...