Theoretical study on the reaction mechanism and thermodynamics of tin oxidation by oxygen species and chlorine species

In this work ab initio molecular orbital methods were employed to study the coal combustion reaction mechanisms of tin oxidized by different oxidants, including HOCl, HCl, ClO, ClO₂, NO₃, CO₂, and O₂. Eleven reaction pathways were identified. The results show that Sn can react with HCl, ClOO, CO₂, O₂, and NO₃ to form SnO and SnCl. SnO can be oxidized into SnCl by HOCl and HCl. SnCl can be further oxidized into a soluble compound, SnCl₂. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

掺杂NASICON系统的23Na NMR研究

化合物Na3Zr2Si2PO12。是由ZrO6八面体与SiO4或PO4四面体共角构成的开放三维骨架结构，Na 位于骨架间隙，称之为NASICON（NaSuperIoaicConductor），具有和Na－Al2O3相似的离子电导率（在300℃时，σ＝0．2Ω－1·cm-1［1］但是由于该化合物在100－2000℃间存在单斜一、立方的可逆相变，使其应用受到限制．为了抑制这种相变，已进行了骨架掺杂的研究工作，制备出了多种化学掺杂的NASICON系统［2］．在Na3Zr2Si2PO12化合物中，三个Na十分别位于结构中两个不同的位置，然而掺杂以后，骨架结构发生变化，这时Na十位置，将关系…     

Palladium catalyzed Suzuki coupling reactions using cobalt-containing bulky phosphine ligands

Three bulky mono-dentate alkyne-bridged dicobalt-phosphine complexes [(μ-PPh₂CH₂PPh₂)Co₂(CO)₄](μ,η-PhCCPPh₂) 4a, [(μ-PPh₂CH₂PPh₂)Co₂(CO)₄](μ,η-Me₃CCCPPh₂) 5a and [(μ-PPh₂CH₂PPh₂)Co₂(CO)₄](μ,η-Me₃SiCCPPh₂) 6a were prepared from the reactions of the bis(diphenylphosphino)methylene (dppm) bridged dicobalt complex Co₂(CO)₆(μ-Ph₂PCH₂PPh₂) with PhCCPPh₂1, Me₃CCCPPh₂2, and Me₃SiCCPPh₂3, respectively. These three metal-containing compounds 4a, 5a and 6a were employed as ligands, replacing conventional organic phosphines, in the Suzuki cross-coupling reactions and have been proved to be effective, authentic mono-dentate phosphine ligands.     

Kinetics and Mechanisms of Acetylcholinesterase and Butyrylcholinesterase Inhibition by Cardiovascular Drugs and Benzodiazepines

The goal of this work is to determine enzyme kinetics and mechanisms of acetylcholinesterase and butyrylcholinesterase inhibition by five cardiovascular drugs, lovastatin, simvastatin, amlodipine besylate, nifedipine, and hydralazine hydrochloride, and two benzodiazepines, diazepam and chlordiazepoxide hydrochloride. All drugs in this study are reversible mixed‐type inhibitors of acetylcholinesterase and butyrylcholinesterase. The pK_i values for acetylcholinesterase and butyrylcholinesterase inhibition by the cardiovascular drugs are linearly correlated with the molecular weights of the drugs with the slopes of 0.005 and 0.0021, respectively. Therefore, van der Waals' interactions between acetylcholinesterase and the cardiovascular drugs are stronger than those between butyrylcholinesterase and the drugs. This is probably due to a smaller active site gorge and a more significant peripheral anionic substrate binding site of acetylcholinesterase than those of butyrylcholinesterase. The fact that the pK_i values for both butyrylcholinesterase and acetylcholinesterase inhibition by the cardiovascular drugs are linearly correlated with each other suggests that both enzyme inhibition reactions proceed via a common mechanism. Furthermore, amlodipine besylate may be useful in Alzheimer's disease treatment similar to donepezil.     

Sol-gel processing of lead-free (Na,K)NbO<Subscript>3</Subscript> ferroelectric films

The sol-gel processing of lead-free (Na,K) NbO₃ ferroelectric films was studied. Sodium ethoxide (NaOC₂H₅) and potassium ethoxide (KOC₂H₅) were prepared by reacting solid Na and K with ethanol (99.7%) in a solvent of 2-methoxyethanol. 0.5-μm-thick (Na,K)NbO₃ thin films with orthorhombic perovskite structure were obtained by pyrolyzing at 400°C and annealing at 800–900°C. The films had relatively dense and uniform microstructure with grain size of about 50 nm, whose ferroelectricity was proved by the P-E hysteresis loop measurement. It was found that excess K was effective to reduce the annealing temperature for the crystallization of sol-gel-derived (Na,K)NbO₃ thin films.     

酶-配体复合物亲和性的计算

描述了一种新的计算酶－配体复合物亲和性的方法．它考虑了酶－配体结合过程中自由能变化的各主要因素，并利用经验公式加以计算、从蛋白质结构数据库中选取了66个酶－配体复合物作为训练集，利用回归分析得出最后的模型．此模型通用于各种类型的酶－配体复合物，计算结果比技准确，预测算合物解离常数的平均偏差小于一个数量级．此方法还可以定量评价配体分子中每个部分对结合过程的贡献大小，可以为先导他合物的优化提供非常直接的信息     

Direct Electrochemistry of Hemoglobin Immobilized on Carbon‐Coated Iron Nanoparticles for Amperometric Detection of Hydrogen Peroxide

A novel method for preparation of hydrogen peroxide biosensor was presented based on immobilization of hemoglobin (Hb) on carbon‐coated iron nanoparticles (CIN). CIN was firstly dispersed in a chitosan solution and cast onto a glassy carbon electrode to form a CIN/chitosan composite film modified electrode. Hb was then immobilized onto the composite film with the cross‐linking of glutaraldehyde. The immobilized Hb displayed a pair of stable and quasireversible redox peaks and excellent electrocatalytic reduction of hydrogen peroxide (H₂O₂), which leading to an unmediated biosensor for H₂O₂. The electrocatalytic response exhibited a linear dependence on H₂O₂ concentration in a wide range from 3.1 μM to 4.0 mM with a detection limit of 1.2 μM (S/N=3). The designed biosensor exhibited acceptable stability, long‐term life and good reproducibility.     

Tetracarbonyliron adducts of Cp2Cr2(CO)4(μ-η2-P2). Syntheses and crystal structures of Cp2Cr2(CO)4P2[Fe(CO)4] m (m=1 and 2)

Cp₂Cr₂(CO)₄( - ² - P₂), 1, reacts with one molar equivalent of Fe₂(CO)₉ in THF to yield the mono- and di-iron complexes, Cp₂Cr₂(CO)₄P₂[Fe(CO)₄], 2, (16.5% yield) and Cp₂Cr₂(CO)₄P₂[Fe(CO)₄]₂, 3, (16.9% yield), as dark magenta brown and dark greenish brown crystals, respectively. Both complexes were characterized by single-crystal X-ray diffraction analysis. Crystal data –2: space group =P2₁/c,a=17.024(1) Å,b=8.180(1) Å,c=30.891(2) Å, =100.953(5)°,V=4223.4(7)ų,Z=8, 3743 observed reflections,R _F=0.033; 3: space group P1,a=10.209(2) Å,b=10.212(2) Å,c=15.989(3) Å, =106.93(1)°, =91.87(1)°, =119.50(1)°,V=1356.5(4) ų,Z=2, 3489 observed reflections,R _F=0.029.     

Distorted hexagonal phase studied by neutron diffraction: lipid components demixed in a bent monolayer

The recent discovery of a distorted hexagonal phase in 1,2-dioleoyl-sn-glycero-3-phosphatidylethanolamine/1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPE/DOPC) mixtures raised the intriguing question as to whether lipid mixtures demix in a bent monolayer. We performed neutron diffraction on a mixture of headgroup deuterated DOPC-d(13) and nondeuterated DOPE to study the lipid distribution in the distorted hexagonal phase. The 1:1 lipid mixture in full hydration and 25 degrees C was in a homogeneous lamellar phase. Upon dehydration the mixture transformed to a rhombohedral phase, then to a distorted inverted hexagonal phase, and finally to a regular inverted hexagonal phase. In the distorted hexagonal phase, the diffraction pattern showed a two-dimensional monoclinic lattice with two reciprocal vectors of equal length (1.5 nm(-)(1)) forming an angle 53 degrees between them. Diffraction intensities measured while varying the D(2)O/H(2)O ratio in the humidity was used to solve the phase problem. The neutron scattering length density distribution of the distorted hexagonal phase was constructed. The constant density contours are approximately elliptical. The difference in the eccentricities of the contours between the water and lipid distributions indicates that the DOPE/DOPC ratio is not uniform around the elliptical lipid tube in the unit cell. DOPE is preferentially distributed at the vertex regions where the curvature is the highest. Thus for the first time it is shown that when a monolayer of a homogeneous lipid mixture is bent, the lipid components are partially demixed in reaching the free energy minimum.