摘要:

AbstractWe have studied the size‐dependent inhibition capabilities of colloidal selenium (Se) particles on lipopolysaccharide (LPS)‐induced nitric oxide (NO) production in RAW 264.7 cells. Four particle sizes of the nano‐Se, ranging from 45 ˜ 220 nm in diameter, were examined. All of them, unlike their bulk material, show clear capabilities of inhibition and a trend dependent on the particles size. The inhibition becomes more potent as the particle size increases. It indicates that pursuing the reduction of colloidal sizes into nanoscale is not favoured in this biological

ISSN:0009-4536    

DOI:10.1002/jccs.200500058

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY

摘要:

AbstractFrom the changes in energy band, density of state (DOS) and electronic structure calculated by the DFT/B3LYP method, the conductivity of carbon doped boron‐nitride nanotube (BNNT), which is formed by C‐C bond substituting B‐N bond, was discussed. The results indicate that the substitution will strengthen the conductivity of the tube, and its semi‐conductivity might be adjusted by controlling the subst

ISSN:0009-4536    

DOI:10.1002/jccs.200500059

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY

摘要:

AbstractUsing the hemin‐H2O2‐Na2CO3‐NaOH chemiluminescence (CL) system, the study on the photodecomposition behavior of hemin under ultraviolet light and solar light were carried out and the determination of hemin was developed coupled with simple flow injection technique. The results showed that the decomposition reaction of hemin in different light irradiations corresponded with a first‐order reaction. And then the determination of hemin was completed by the CL emission from the reaction of hemin with H2O2in aqueous carbonate. The linear range was 2.2 × 10−10to 6.88 × 10−7M and the detection limit was 2.2 × 10−11M (S/N = 3). The relative standard deviation (RSD) was 2.82% for ten independent detections of 1.72 × 10−8M hemin. As a preliminary application, the proposed method was successfully applied for the analysis of hemin in pharmaceutical formulations and animal blood with a recovery of 96˜108%. A possible CL mechanism of the present system was discussed, and free radicals were suggested to be invol

ISSN:0009-4536    

DOI:10.1002/jccs.200500060

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY

摘要:

AbstractDensity Functional Theory (DFT) calculations have been performed on the high explosive compound tetranitrotetraazabicyclooctane (bicyclo‐HMX) in gas phase employing the self‐consistent field (SCF) theory and in different solvents, i.e. cyclohexane, dichloroethane, ethylalcohol, acetonitrile, and water, utilizing the self‐consistent reaction field (SCRF) theory at a B3LYP/6–31 1G** level of theory. Reasonable agreement has been found between the computed and the available experimental data. The effects of different solvents on the geometry, electronic structure, and vibrational frequencies are discussed. Various solvents under consideration are found to have similar effects on the above properties. But some properties change regularly with the increasing polarity of the solvents, and the stronger the solvent polarity is, the larger the change is. In addition, based on the vibrational analysis, standard thermodynamic properties of bicyclo‐HMX in gas phase are also computed by using the statistical thermodynamic

ISSN:0009-4536    

DOI:10.1002/jccs.200500061

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY

摘要:

AbstractOn the basis of density functional theory, the spin ground state of chromium‐nitrosyl complex [Cr(H2O)5NO]2+(S = 1/2) is studied via B3LYP hybrid method. Its vibrational frequencies, atomic charges, and spin densities are analyzed. The excitation energies are evaluated using the CIS method. Our calculated N‐O stretching frequency and excitation energies are in good agreement with the IR and UV‐vis data. The related CrI(H2O)6+, CrII(H2O)62+, and CrIII(H2O)63+complexes are employed as the reference compounds to determine the characteristics of the central Cr. Results indicate that the effective Cr oxidation state is close to

ISSN:0009-4536    

DOI:10.1002/jccs.200500062

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY

摘要:

AbstractAb initioand DFT(B3LYP) levels of theory, with basis sets of 3–21G, 6–31G*, and LanL2DZ, have been applied to the specific DNA binder Hoechst 33258. All calculations lead to a structure with two benzimidazole groups and one phenyl group being coplanar. Atoms H33and H37bear large positive charges, and the distance between the two atoms is about 5 Å, which allows the molecule interacting with the negative sites of neighboring bases in the DNA helix and thus facilitates Hoechst 33258 to gravitate on AT‐rich regions in the minor groove of DNA, owing to the deeper negative potential in such sequences. The most stable conformer corresponds to the dihedral angles of ca. 0° for ϕ1‐2‐14‐15and ϕ27‐26‐5‐4, and 180° for ϕ20‐19‐11‐12. This fact provides clear evidence that Hoechst 33258 has an arc‐like shape with coplanar aromatic rings. Both the HOMO and the LUMO are made up of thePzorbitals of the non‐hydrogen atoms in two benzimidazole groups and one phenyl group. On going from the ground state to the first singlet excited state, the lengths of the single bonds between the aromatic rings decrease, and the aromatic rings are more conjugated with each other in the excited state. The heat of formation(ΔHf)of Hoechst 33258, evaluated from the isodesmic reaction, is 406.3

ISSN:0009-4536    

DOI:10.1002/jccs.200500063

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY

摘要:

AbstractThis article presents rotating ring‐disc electrode investigations of (A = alanine, F = phenylalanine, G = glycine, L = leucine, W = tryptophan) W, GW, WGG, GWG, GGW, GWGG, and GGWA. In addition, the analyses of the copper complexes of the same peptides plus GF, FGG, GFG, FGG, GGFL, GGGG, AAAA, and GGGGGG have been carried out. The results suggest that an influential step in the reaction mechanism of the copper complexes of the tryptophan‐containing peptides (W‐peptides) is the alteration of the peptide structure after the one‐electron oxidation of tryptophan. This change in structure leads to a positive shift in redox potential for the Cu(III)/Cu(II) couple. The analytical implications for the electrochemical detection of W‐peptides as their copper complexes are applied for detection of W‐containing bioactive peptides. Application of the optimized detection conditions of peptides as their Cu(II) complexes are as follows: (1) If sensitivity is paramount, detect the copper complexes at a relatively high potential, around 0.7 V vs. Ag/AgCl. (2) If selectivity is paramount, use a dual electrode detector, oxidize at an upstream anode at 0.4 V, and detect at the downstream cathode

ISSN:0009-4536    

DOI:10.1002/jccs.200500064

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY

摘要:

AbstractA water in soluble long‐chain crown ether alkyl (C18)‐benzo‐15‐crown‐5 was synthesized and applied as a coating material on quartz crystal membranes of a liquid flow piezo electric crystal sensor. The oscillating crown ether‐coated piezo electric (PZ) crystal with a home‐made computer inter face was prepared as a liquid chromato graphic (LC) detector for organic species and metal ions in aqueous solutions. The oscillating frequency of the quartz crystal decreased due to the adsorption of organic molecules or metal ions on crown ether molecules. Effects of functional group, molar mass, steric hindrance, and polarity of organic molecules on frequency responses of the crown ether coated PZ crystal detector were investigated. The frequency responses of the crown ether coated PZ crystal detector for various molecules were in the order: amines>carboxylic acids>alcohols>ketones. The crown ether PZ detector also exhibited good sensitivity for some heavy metal ions and the frequency shifts were in the order: Cr3+» Pb2+>Co2+>Cd2+>Ni2+>Cu2+. The crown ether coated piezo electric crystal LC detector demonstrated low detection limits for various polar organic molecules, e.g., 6.0 × 10−5M for propylamine, and metal ions, e.g., 2.9 × 10−5M (1.8 ppm) for Cu2+; the crown ether PZ detector also gave good reproducibility when re used. A quite sensitive electrochemical quartz crystal microbalance (EQCM) detection system was also set‐up for detecting trace heavy metal ions in solutions. The variation in frequency of the PZ crystal and the diffusion current were observed simultaneously after the reduction in heavy metal ions such as Cu2+and Ni2+. The EQCM detection system exhibited fairly good sensitivity, e.g., 112 Hz/ppm for Cu2+and a good detection limit, e.g., 0.13 ppm for Cu2+ions. Comparison between EQCM and PZ detection systems

ISSN:0009-4536    

DOI:10.1002/jccs.200500065

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY

摘要:

AbstractThe reductions of Co(terpy)23+and Co(edta)−complexes by ascorbic acid have been subjected to a detailed kinetic study in the range of pH =1–10.9. For each complex the rate law of the reaction is interpreted as a rate determining reaction between Co(III) complex and the ascorbic acid in the form of HA−(k1) and A2−(k2), depending on the pH of the solution, followed by a rapid scavenge of the ascorbic acid radicals by Co(III) complex. With given Ka1and Ka2, the rate constants are k1= 0.25 and 9.87 × 10−5M−1s−1, k2= 1.28 × 106and 18.7 M−1s−1for Co(terpy)23+and Co(edta)−complexes, respectively, at T = 25 °C and μ = 0.50M (terpy)and 1.0 M (edta) HClO4/LiClO4. The mechanism of the reaction is discussed on the basis of Marcus theory for outer sphere electron transfer process. Spin change and charge effect, duly considered, account for the non‐adiabatic behavior in the redu

ISSN:0009-4536    

DOI:10.1002/jccs.200500066

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY

摘要:

AbstractTwelve new germanium substituted diphenyltin dipropionates with the general formula (R1GeCHR2‐CHR3COO)2SnPh2where R1= N(CH2CH2O)3, (C6H5)3and (CH3C6H4)3, R2= H, CH3, C6H5, p‐CH3C6H4, p‐CH3OC6H4, p‐ClC6H4, and R3= H, CH3have been synthesized by the reaction of diphenyltin oxide with a germanium substituted propionic acid. All the compounds were characterized by elemental analysis, IR, multi‐nuclear (1H,13C,119Sn) NMR and Mössbauer spectroscopies as well as mass spectrometry. Thein vitroantibacterial activity of selected compounds is als

ISSN:0009-4536    

DOI:10.1002/jccs.200500067

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY