Two new compounds from Zingiber officinale

A new cyclic diarylheptanoid,1,5-epoxy-3-hydroxy-1-(3-methoxy-4,5-dihydroxyphenyl)-7-(4-hydroxyphenyl)-heptane (1),as well as a new monoterpene,10-O-β-D-glucopyranosyl-hydroxy cineole (2) were isolated from the rhizomes of Zingiber officinale. The structures of compounds 1 and 2 were established based on their spectral data.In addition,the antioxidant activities of these compounds were also measured.     

Concise Synthesis and Antimicrobial Activities of New Substituted 5‐Isoxazolpenicillins

The synthesis of a series of new 5‐isoxazolpenicillins is described, which were obtained by coupling substituted isoxazoles with 6‐APA. Concise large‐scale synthesis of 3,5‐disubstituted isoxazoles by 1,3‐dipolar cycloaddition using copper(I) as catalyst was also investigated. Representative compounds were assayed for antimicrobial activities, showing satisfactory antimicrobial activities against Gram‐negative bacteria.     

Radiation effects in the transient hot-wire technique

The transient hot-wire technique is widely used for absolute measurements of the thermal conductivity and thermal diffusivity of fluids. It is well established that fluid radiation effects significantly influence these measurements, especially those for the thermal diffusivity. Corrections for radiation effects are based on the models developed and deviations of the measured data from the ideal line source model. In this paper, the effect of fluid radiation on the measurements of the thermal conductivity of n-pentane is presented. For comparison, the influence of thermal radiation effect on measurement of transparent fluids, such as argon is also shown. The difference between the influence of natural convection and thermal radiation is also demonstrated.     

Theoretical prediction of the contact distance dependence of the electron transfer reactivity of the ClO/ClO− coupling system

On the basis of the structures and properties of the ClO/ClO^? system obtained at the density functional theory (DFT) (UB3LYP) level, employing the 6‐311+G(3df) standard basis set, the electron transfer reactivity of this system is investigated. The results indicate that there are five possible stable coupling complexes that correspond to the generous minima on the global potential energy surfaces (PES). The most stable coupling complex is planar EC4, in which there is a O? O linkage with two trans‐Cl atoms. Their stabilization energies are calculated to be 20.57 (EC1: C₁), 20.54 (EC2: C₂, ²B), 20.69 (EC3: C₁), 20.70 (EC4: C_s, ²A′), and 20.69 (EC.5: C_2h, ²B_u) kcal/mol at the B3LYP/6‐311+G(3df) level; with the correction of the basis set superposition error (BSSE), the stability order of these encounter complexes is EC4 > EC.5 > EC3 > EC1 > EC2. Based on the five encounter complexes, five coupling modes are designed for the study of the electron transfer reactivity of this system. The dissociation energy curves at the activated states and the corresponding activation energies of these five coupling modes are obtained and are compared at the B3LYP/6‐311+G(3df) and MP2/6‐311+G* levels. The inapplicability of DFT methods has also been discussed in this article in predicting the energy curves, especially with a long contact distance, in which DFT methods give the abnormal behavior for the dissociations of the complexes caused by the “inverse symmetry breaking” problem. On the basis of the golden rule of the time‐dependent perturbation theory, the electron transfer reactivity and the contact distance dependence of the various electron transfer kinetics parameters (e.g., activation energy, coupling matrix element) have been analyzed at the UMP2(full)/6‐311+G* level. The electron transfer can take place over a range of contact distances, but the most effective coupling distance corresponds to only a small range. The coupling orientation analyses also indicate that the most favorable coupling mode to the electron transfer does not always correspond to the most stable encounter complex mechanism. Some highly energetic coupling modes are more favorable for the electron transfer. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

NITROXIDE-MEDIATED FREE RADICAL SYNTHESIS OF MESOGEN-JACKETED LIQUID CRYSTAL POLYMERS*

The first TEMPO-mediated "living" free radical polymerization of liquid crystallinemonomer, 2, 5-bis[(4-methoxyphenyl)oxycarbonyl]styrene(MPCS), was carried out at 130℃ withBPO as an initiator. The molecular weight of the polymer can be varied from rather low values to highvalues while maintaining narrow polydispersity. It was observed that the polymerization of MPCSproceeded much faster than that of styrene. A tentative explanation for this fast polymerization wassuggested.     

Thermal Behaviour and Decomposition Kinetics for Two Palladium(II) Complexes with 1-aminopyrene and its Derivative

The thermal decomposition studies for two palladium(II) complexes Pd(apyr)₂Cl₂ and Pd(pmpa)Cl₂ (apyr=1–aminopyrene and pmpa=N–(2–pyridylmethylene)–1–pyrenylamine) were carried out in pure nitrogen using TG-DTG techniques. The non-isothermal kinetic parameters for the two complexes were evaluated employing the method suggested by Málek, esták, Koga et al. Based on the above results, thermal behaviour of the complexes were carefully discussed, which showed that not only the parameters value, but also the decomposition pattern and mechanism for complex 1 are different from complex 2.This revised version was published online in November 2005 with corrections to the Cover Date.     

Application of water as a solvent in microwave-assisted extraction for analysis of PCBs and CBzs in fly ash

Polychlorinated biphenyls (PCBs) and chlorobenzenes (CBzs) are two classes of dioxin precursors formed in municipal solid waste incinerators (MSWIs); they produce negative health effects similar to those of dioxins. Reducing the analytical time required for determining the concentrations of these compounds in MSWIs is important for quickly evaluating their importance and assessing associated health risks. In the present study, water is used as a safe and environmentally friendly solvent in microwave-assisted extraction (MAE) for PCB and CBz analyses. MAE is compared with traditional Soxhlet extraction (SE) to determine the extraction efficiencies. The evaluation of extraction efficiencies shows that MAE has a high extraction efficiency compared with that of SE when water content is lower than 60%. Furthermore, the extraction time and organic solvent consumption are reduced with MAE compared with SE.     

新型纤维素衍生物手性固定相的制备及其对几种对映异构体的高效液相色谱分离

合成了一种经环十二烷修饰的纤维素酯，将其涂敷于小粒径的氨丙基化硅胶（APS）上，制备出高效液相色谱手性固定相，以正己烷、异丙醇为流动相拆分了2-对氯苯基丙腈、1-对氟苯基乙醇、1-对叔丁基苯氧基-2-丙醇、2-对氯苯基辛腈及三唑醇等5种外消旋对映体，并考察了流动相中异丙醇含量对分离效果的影响。     

Affinity Chromatography of Insulin with a Heptapeptide Ligand Selected from Phage Display Library

A heptapeptide phage display library was screened with insulin to find its ligands for affinity chromatography. The peptide was synthesized and coupled to EAH Sepharose 4B (5.4 mol mL^–1 bed). Then, insulin chromatography was carried out with mobile phases of different pH values and by the addition of urea and ethylene glycol. It was found that electrostatic interactions were predominant for the affinity binding, and hydrogen bonding might also contribute somewhat to the affinity. Finally, frontal analysis was performed and the dynamic binding capacity of the affinity column for insulin at 50% breakthrough was estimated at 60.6 mg mL^–1 bed, which was about two times higher than the theoretical binding capacity of the monomeric insulin. The result suggests that insulin was bound in dimer state in a stoichiometric relationship with the coupled peptide, indicating the high binding efficiency of the peptide ligand for insulin.     

Synthesis and structure of Mn(II) and Zn(II) complexes containing 1,10-phenanthroline unit

The Mn(II) and Zn(II) complexes of N,N′-diisopropyl-1,10-phenanthroline-2,9-dimethanamine have been synthesised, and the structure of the two complexes have been studied by X-ray crystallography.