Iliaš et al. analyzed the spectroscopic properties of PbO and PbO−, incorporating relativistic effects at several levels: spin-free, two-component infinite-order Douglas–Kroll–Hess, four-component Dirac–Coulomb, and the restricted active space state interaction spin-orbit.Proper treatment of basis set effects, electron correlation, and relativistic effects including the spin–orbit coupling are necessary for accurate calculation of the spectroscopic properties of the lead oxide, its anion, and the electron affinity of the PbO.In this paper, the culture of quantum chemistry and life in Denmark are also briefly touched upon.
The phase diagram of a Lennard-Jones system was estimated using conventional NPT molecular dynamics (MD) simulations. The standard cyclic boundaries were assumed. An elongated unit cell with both solid and fluid sections was found to be suitable as a model during the NPT MD simulations when calculating both the melting and vapor pressure curves. This unit cell contained 1000 molecules, of which, in the initial state, half were assigned to an FCC structure while the remainder had a density close to that of the critical state. The results of these simulations were compared with those of phase-1/phase-2 coexistence simulations and also with reported experimental data. The triple point was obtained by NVE MD calculations based on a unit cell containing both solid and gaseous sections, while the critical point was estimated by NVE MD using an elongated unit cell with a density near the critical value. Sublimation pressure was calculated by NVT MD with a unit cell again containing both solid and gaseous sections.
Aminopeptidases remove the N-terminal amino acids from proteins by hydrolysis. Previously we synthesized an aminopeptidase mimic [Zn2(bomp)(OCOCH3)2]BPh4 [bomp− = 2,6-bis[bis(2-methoxyethyl)aminomethyl]-4-methylphenolate] and reported that the aminopeptidase mimic hydrolyzed L-leucine-p-nitroanilide as a substrate. Although the structure of the aminopeptidase mimic was determined by single-crystal X-ray diffraction method, the structure of the substrate incorporation mode (how the substrate was incorporated) was not clarified. Therefore, in this study, we investigate the substrate incorporation mode using the technique of conformational analysis based on the Density Functional Theory (DFT). We have found an efficient incorporation mode for the aminopeptidase-like reaction. In the structure the substrate is incorporated in its best conformation, and the Zn-OH nucleophile is very close to the substrate. Moreover, one of the chelating arms of the ligand (bomp−) is hydrogen-bonded to the Zn-OH nucleophile, so the arm is expected to work as a general base catalyst capable of enhancing the Zn-OH nucleophile. Furthermore, the other zinc(II)ion is expected to work as a general acid catalyst capable of enhancing the electrophilicity of the carbonyl carbon on the substrate. We have concluded that the aminopeptidase activity is expected to be increased if the ratio of the efficient substrate incorporation mode is increased.
Equations of state (EOSs) are proposed for a system consisting of a perfect solid and a perfect liquid made up of single spherical molecules. The Lennard-Jones interaction is assumed for this system. Molecular dynamics simulations are performed in order to determine the temperature and density dependences of the internal energy and pressure. The supercooled liquid state is also examined. The internal energy term in the EOSs is the sum of the average kinetic and potential energies at 0 K and the temperature-dependent potential energy. The temperature-dependent term of the average potential energy is assumed to be a linear function of temperature, and its coefficient is expressed as a polynomial function of the number density. The pressure is expressed in a similar manner, where the pressure satisfies the thermodynamic EOS. The equilibrium condition is solved numerically for the phase equilibrium of argon. The Gibbs energy provides a reasonable transition pressure for three-phase equilibrium in argon. The thermodynamic properties at low pressures have significant temperature dependences. The linear character of the pressure and internal energy as functions of temperature in the condensed phases is discussed based on the short-term vibration motion.