ABSTRACT
Hydrogen abstractions by NO2 from symmetric ethers are investigated to determine the rate constants and explore the effect of the functional group on rate constants at different reaction sites. The involved ethers are dimethyl ether (DME), diethyl ether (DEE), dipropyl ether (DPE), and dibutyl ether (DBE). The B3LYP method with a 6-31G(2df,p) basis set is employed to optimize the ground-state geometries and for frequency and intrinsic reaction coordinate calculations. The G4 method is used to calculate the electronic energies for the small ethers (DME and DEE). Given the heavy computational cost of the G4 method, the modified G4MP2 method is applied for larger ethers (DPE and DBE) and also for DME to verify the accuracy of the G4MP2 method by benchmarking with the G4 method. The high-pressure limit rate constants are calculated within the temperature range of 500-2000 K, with the asymmetrical Eckart tunneling correction as well as one-dimensional hindered rotor treatment. The calculated rate constants agree well with the literature data, and the branch ratio analysis suggests that the cis-HONO channel basically dominates the hydrogen abstraction reactions and shows a decrease at high temperatures, followed by HNO2 and trans-HONO channels; in addition, the hydrogen abstraction at the C site adjacent to the ether bond (α reaction site) accounts for most of the reactions. Furthermore, the total rate constants of the ethers are compared to those of their half-structurally alkanes, and linear Bell-Evans-Polanyi correlations are observed.
ABSTRACT
Molecular dynamics (MD) simulation was used to study chitosan behaviors on different hydroxyapatite (HA) crystallographic planes at the atomic level. The interaction energy between the chitosan chain and different HA surfaces indicates that the interaction of the chitosan chain and HA(1 0 0) surfaces is stronger than that of HA(0 0 1) and HA(1 1 0) surfaces. The chemical interactions between chitosan and HA were analyzed through the concentration profile and pair correlation function of nitrogen and oxygen atoms in chitosan. The results show that there might be chemical interaction between nitrogen and calcium atoms, and hydrogen bonding between oxygen atoms and hydroxyl groups. This study provides useful information in understanding the interfacial interaction mechanism at the atomistic scale.
Subject(s)
Durapatite/chemistry , Polymers/chemistry , Biocompatible Materials , Biopolymers/chemistry , Chitosan/chemistry , Computer Simulation , Crystallography, X-Ray/methods , Humans , Materials Testing , Models, Chemical , Models, Statistical , Molecular Conformation , Nitrogen/chemistry , Oxygen/chemistry , Surface PropertiesABSTRACT
Ro 40-5967 is a structurally novel Ca2+ channel blocker which binds to the [3H]desmethoxyverapamil receptor in cardiac membranes with a potency similar to that of verapamil but which has considerably fewer negative inotropic effects. In the present study, the inward Ca2+ current was measured in isolated myocytes with the whole-cell patch-clamp technique. It was found that at a physiological membrane potential (-80 mV) Ro 40-5967 was also less potent than verapamil in inhibiting this current, and that negative inotropy and Ca2+ channel blockade were correlated.
Subject(s)
Benzimidazoles/pharmacology , Calcium Channels/drug effects , Myocardial Contraction/drug effects , Tetrahydronaphthalenes/pharmacology , Verapamil/pharmacology , Animals , Calcium Channel Blockers/pharmacology , Depression, Chemical , Guinea Pigs , In Vitro Techniques , Membrane Potentials , MibefradilABSTRACT
This study investigated, with microelectrode technic, the effects of electrical activities in pacemaker cells of sinoatrial node by Qixue injection consisting of Ginseng, Astragali and Angelicae sinensis, which may replenish the Qi and invigorate the circulation of blood. Qixue injection produced a negative chronotropic action on beating of sinoatrial node mainly because of lowering the rate of diastolic automatic depolarization and lengthening the duration of diastolic depolarization as well, but this action was caused through neither cholinergic M receptors nor adrenergic beta receptors. With hypoxia at temperature of 41 degrees C or with isoprenaline in existence to cause beating slowness and arrhythmia, Qixue injection turned them into rhythmical beating and quickened automatic beating frequency. It suggested that Qixue injection could antagonize pathologic changes caused by insufficiency of oxygen supply and improve function of sinoatrial node. Also it indicated that Qixue injection had a biphasic function on regulating rhythmical activities of sinoatrial node, which might be one of the mechanisms of the drug used clinically.
Subject(s)
Drugs, Chinese Herbal/pharmacology , Sinoatrial Node/drug effects , Action Potentials/drug effects , Animals , In Vitro Techniques , Microelectrodes , Panax , Plants, Medicinal , Rabbits , Sinoatrial Node/cytologyABSTRACT
X-ray investigation was made on the knee joint in 122 individuals, both AP and lateral radiographs were taken. The result showed that the intercondylar eminence of tibia develops at a certain period after birth, the time to make its appearance is 6-10 years for female and 7-10 years for male. The initial appearance often takes the form of a localized prominence usually single. The various configurations of the intercondylar eminence, the angle, height and density were described.
