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.     

Synthesis and derivatisation of a novel spiro[1-benzofuran-2,4'-piperidin]-3-one scaffold

The synthesis of a novel spiro[1-benzofuran-2,4'-piperidin]-3-one scaffold has been achieved in five steps with an overall yield of 47%. The versatility of the spiropiperidine scaffold in the context of library synthesis is exemplified by selective and sequential derivatisation of the amino and aryl bromide functional groups, including the development of multi-step telescope reaction matrices.     

Synthesis of constrained analogues of cholecystokinin/opioid chimeric peptides

In our ongoing research on the synthesis of constrained analogues of CCK/opioid chimeric peptides, a bicyclic dipeptide mimetic for Nle-Asp was designed and synthesized. Starting from β-allyl substituted aspartic acids, the terminal double bond was oxidized resulting in spontaneous cyclization to form racemic hemiaminals. Allylation of the hemiaminals afforded 5-allyl substituted proline analogues, which on oxidation, Horner-Emmons olefination, asymmetric hydrogenation, and bicyclization afforded bicyclic dipeptide mimetics for Nle-Asp. Constrained CCK/opioid peptide analogues containing bicyclic dipeptide mimetics for Nle-Gly, Nle-Asp, and homoPhe-Gly were then synthesized and analyzed at both the CCK and opioid receptors.     

First synthesis of perfluorinated corrole and its mn=o complex

A novel perfluorinated corrole, 2,3,7,8,12,13,17,18-octafluoro-5,10,15-tris(pentafluorophenyl)corrole, and its manganese(III) and oxomanganese(V) derivatives have been synthesized. The perfluorinated manganese corrolate exhibited excellent reactivity and stability in the catalytic oxidation of alkenes with iodosylbenzene.     

CH3(2A′)自由基与臭氧反应机理的量子化学研究

用量子化学UMP2方法，在6-311++G**基组水平上研究了CH3(2A′)自由基与臭氧反应机理，全参数优化了反应过程中反应物、中间体、过渡态和产物的几何构型，在UQCISD(T)/6-311++G**水平上计算了它们的能量；并对它们进行了振动分析，以确定中间体和过渡态的真实性；同时应用经典过渡态理论计算了反应的速率常数，并与实验值进行了比较, CH3自由基与臭氧反应速率常数的理论计算结果为: 4.73×10－14 cm3•molecule－1•s－1，与实验报导的结果(k=2.52×10－14 cm3•molecule－1•s－1)很接近，同时发现CH3(2A′)自由基与O3的反应是强放热反应.     

Kinetics of the Reduction of Cupric Ion in Ammonia Solution by Sulfur Dioxide

The reduction of cupric ion in ammonia solution by aqueous sulfur dioxide was studied. Each run was carried out at constant initial cupric concentration, stirred rate and total mixed gas flow rate. The effect of temperature, partial pressure of sulfur dioxide in gas phase and cupric ion concentration of the solution was investigated. The reaction of Cu³⁺+SO₂(aq.)→Cu⁺+SO₄^2? was carried out by bubbling mixed gas (SO₂/N₂) through the aqueous ammonia complex of copper (II). The color change for the system was from deep blue, green, yellow to white. The pH values in the system changed from 10 to 4. The product of the reaction was identified by the analyses of IR spectrum and X-ray diffraction, having the formula of 7Cu₂SO₃· 2CuSO₃·3(NH₄)₂SO₃·24H₂O. The kinetic model of the reduction was proposed as: –d[Cu²⁺]/dt = k exp(–E/RT)[Cu²⁺]α[SO₂%] According to the experiments, the parameters were determined as: α=1.64±0.03, þ=1.20, E=13.7 Kcal/mol and k = (1.77±0.20)×10¹⁰ (g-equ./?)^?0.64min^?2.     

Three Novel Triterpenoids from the Aerial Part of Helwingia chinensis

Three novel triterpenoids named chinenols A – C ( 1 – 3 ), together with two known compounds, glutin‐5‐en‐3β‐ol ( 4 ) and daucosterol ( 5 ), were isolated from the aerial part of Helwingia chinensis Batal . The structures of 1 – 3 were determined on the basis of their HR‐EI‐MS, IR, ¹H‐ and ¹³C‐NMR (DEPT), and 2D (HMQC, HMBC, NOESY) data. Compounds 1 – 3 and 5 showed inhibition activity in an antibacterial assay.