Simple and accurate exchange energy for density functional theory

A non-empirical exchange functional based on an interpolation between two limits of electron density: slowly varying limit and asymptotic limit, is proposed. In the slowly varying limit, we follow the study by Kleinman in 1984 which considered the response of a free-electron gas to an external periodic potential, but further assume that the perturbing potential also induces Bragg diffraction of the Fermi electrons. The interpolation function is motivated by the exact exchange functional of a hydrogen atom. Combined with our recently proposed correlation functional, tests on 56 small molecules show that, for the first-row molecules, the exchange-correlation combo predicts the total energies four times more accurate than presently available Quantum Monte Carlo results. For the second-row molecules, errors of the core electrons exchange energies can be corrected, leading to the most accurate molecular total energy predictions to date despite minimal computational efforts. The calculated bond energies, zero point energies, and dipole moments are also presented.Comment: 1) added derivation of mu value 2) add Quantum Monte Carlo results from Ref.7 for comparisons 3) add total energies, bond energies, dipole moments, and zero point energies prediction

First principle computation of biomolecule -ligand interaction

We have determined the calibration constants for the SDFT prediction of 57Fe Mössbauer parameters. The calibration constants are basis set and exchange-correlation functional specific. The basis set is 6-311G* whereas the exchange-correlation functional are UB3LYP, UBLYP, UBPW91, and UMPW1PW91. This method is used to predict the binding conformation of a dioxygen molecule to the P intermediate of methane monooxygenase whose experimental binding structure is presently unknown. When O2 binds to the diiron cluster in a μ-1,2-peroxo fashion, the associated theoretical Mössbauer parameters are in good agreement with the experimental values. An efficient method for locating minimum energy crossing points is introduced and tested on the phenyl cation. An agreement of the present method and previous works is satisfactory. The convergence rate obeys a logarithmic law and is verified on the phenyl cation. Due to its rapid convergence rate, the method is suitable for a large molecular system. As an application of the new methodology, the crossing points of the cation of [Fe(ptz)6](BF4) 2 were studied in order to identify the geometrical parameters of the spin crossing points between S=0 ↔ S=1, and S=1 ↔ S=2. The calculation shows that the transition from a singlet ground state to the triplet intermediate state is accompanied by almost 0.3Å bond length elongation of the axial ligands. We have implemented an approximation scheme that allows one to study protein system such as a ligand-protein binding conformation and a protein active site geometry optimization. The scheme, named E-MFCC, is a significant improvement over the previous MFCC approximation originally put forth by Zhang et al. The geometry optimization of some small test systems utilizing the E-MFCC scheme introduces an error on the order of 10-2Å as compared to the all-atom calculation

In Vivo Antimalarial Activity of Annona muricata Leaf Extract in Mice Infected with Plasmodium berghei

Malaria is one of the most important infectious diseases in the world. The choice for the treatment is highly limited due to drug resistance. Hence, finding the new compounds to treat malaria is urgently needed. The present study was attempted to evaluate the antimalarial activity of the Annona muricata aqueous leaf extract in Plasmodium berghei infected mice. Aqueous leaf extract of A. muricata was prepared and tested for acute toxicity in mice. For efficacy test in vivo, standard 4-day suppressive test was carried out. ICR mice were inoculated with 107 parasitized erythrocytes of P. berghei ANKA by intraperitoneal injection. The extracts (100, 500, and 1000 mg/kg) were then given orally by gavage once a day for 4 consecutive days. Parasitemia, percentage of inhibition, and packed cell volume were subsequently calculated. Chloroquine (10 mg/kg) was given to infected mice as positive control while untreated control was given only distilled water. It was found that A. muricata aqueous leaf extract at doses of 100, 500, and 1000 mg/kg resulted in dose dependent parasitemia inhibition of 38.03%, 75.25%, and 85.61%, respectively. Survival time was prolonged in infected mice treated with the extract. Moreover, no mortality to mice was observed with this extract up to a dose of 4000 mg/kg. In conclusion, the A. muricata aqueous leaf extract exerted significant antimalarial activity with no toxicity and prolonged survival time. Therefore, this extract might contain potential lead molecule for the development of a new drug for malaria treatment

Antihemolytic Activities of Green Tea, Safflower, and Mulberry Extracts during Plasmodium berghei Infection in Mice

Malaria-associated hemolysis is associated with mortality in adult patients. It has been speculated that oxidative stress and inflammation induced by malaria parasite are involved in its pathophysiology. Hence, we aimed to investigate the antihemolytic effect of green tea, safflower, and mulberry extracts against Plasmodium berghei infection. Aqueous crude extracts of these plants were prepared using hot water method and used for oral treatment in mice. Groups of ICR mice were infected with 6 × 106 infected red blood cells of P. berghei ANKA by intraperitoneal injection and given the extracts (500, 1500, and 3000 mg/kg) twice a day for 4 consecutive days. To assess hemolysis, hematocrit levels were then evaluated. Malaria infection resulted in hemolysis. However, antihemolytic effects were observed in infected mice treated with these extracts at dose-dependent manners. In conclusion, aqueous crude extracts of green tea, safflower, and mulberry exerted antihemolysis induced by malaria infection. These plants may work as potential source in the development of variety of herbal formulations for malarial treatment

Graphs

<b>Figure 1:</b> Hypoglycemia induced by <i>Plasmodium berghei</i> infection.<div><b>Figure 2:</b> Anti-hypoglycemic effect of aqueous crude extract of <i>G. pentaphyllum</i> leaves.<br></div><div><b>Figure 3:</b> Effects of aqueous crude extract of <i>G. pentaphyllum</i> leaves on BW and MST of mice.<br></div

A direct method for locating minimum-energy crossing points (MECPs) in spin-forbidden transitions and nonadiabatic reactions

An efficient computational method for locating minimum-energy crossing points (MECPs) between potential-energy surfaces in spin-crossover transitions and nonadiabatic spin-forbidden (bio)chemical reactions is introduced. The method has been tested on the phenyl cation and the computed MECP associated with its radiationless singlet-triplet spin crossover is in good agreement with available data. However, the convergence behavior of the present method is significantly more efficient than some alternative methods which allows us to study nonadiabatic processes in larger systems such as spin crossover in metal-containing compounds. The convergence rate of the method obeys a fast logarithmic law which has been verified on the phenyl cation. As an application of this new methodology, the MECPs of the ferrous complex [Fe(ptz)(6)](BF4)(2), which exhibits light-induced excited spin state trapping, have been computed to identify their geometric and energetic parameters during spin crossover. Our calculations, in conjunction with spin-unrestricted density-functional calculations, show that the transition from the singlet ground state to a triplet intermediate and to the quintet metastable state of [Fe(ptz)(6)](BF4)(2) is accompanied by unusually large bond-length elongations of the axial ligands (approximate to 0.26 and 0.23 angstrom, respectively). Our results are consistent with crystallographic data available for the metastable quintet but also predict new structural and energetic information about the triplet intermediate and at the MECPs which is currently not available from experiment. (C) 2005 American Institute of Physics