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71.
Chin W Dognon JP Piuzzi F Tardivel B Dimicoli I Mons M 《Journal of the American Chemical Society》2005,127(2):707-712
Laser desorption of model peptides coupled to laser spectroscopic techniques enables the gas-phase observation of genuine secondary structures of biology. Spectroscopic evidence for the formation of beta-turns in gas-phase peptide chains containing glycine and phenylalanine residues establishes the intrinsic stability of these forms and their ability to compete with other stable structures. The precise characterization of local minima on the potential energy surface from IR spectroscopy constitutes an acute assessment for the state-of-the-art quantum mechanical calculations also presented. The observation of different types of beta-turns depending upon the residue order within the sequence is found to be consistent with the residue propensities in beta-turns of proteins, which suggests that the prevalence of glycine in type II and II' turns stems essentially from an energetic origin, already at play under isolated conditions. 相似文献
72.
Marie-Hélène Paclet Cécile F. Rousseau Campion Yannick Françoise Morel Anthony W. Coleman 《Journal of inclusion phenomena and macrocyclic chemistry》2006,55(3-4):353-357
The effects of para-Sulphonato-calix[4]arene, para-Sulphonato-calix[6]arene and para-Sulphonato-calix[8]arene on the activation of NADPH oxidase in neutrophils has been studied. All three molecules do not induce NADPH oxidase activation, and hence do not stimulate neutrophils. Measurement of cell viability demonstrates that these three water-soluble calix[n]arene derivatives are not cytotoxic. 相似文献
73.
A. Bärwolff R. Puchert P. Enders U. Menzel D. Ackermann 《Journal of Thermal Analysis and Calorimetry》1995,45(3):417-436
New results of steady-state two-dimensional finite-element computations of temperature distributions of high power semiconductor laser arrays are presented. The influence of different thermal loads on the 2D temperature distribution in AlGaAs/GaAs gain-guided laser arrays is investigated. TheFEM model is tested by comparing it with analytical solutions. For numerical convenience, the latter is rewritten in a novel form, which is free of overflow problems. The maximum temperatures calculated by both methods agree within 1%. Several factors determining the thermal resistance of the device are quantitatively examined: the ratio of light emitting to non-emitting areas along the active zone, the amount of Joule losses, the current spreading, the solder thickness, and voids in the solder. This yields design rules for optimum thermal performance. 相似文献
74.
Why carry out medicinal chemistry at a university, when it means competing with the billion-dollar research efforts of the pharmaceutical industry? In academic research, the race to get a drug to market is not the prime motivation. Instead, university-based medicinal chemistry is driven by the search for new knowledge and the opportunity to educate a new generation of chemists. Furthermore, academia can complement commercial efforts by addressing diseases neglected by private industry. 相似文献
75.
Frère P Allain M Elandaloussi el H Levillain E Sauvage FX Riou A Roncali J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(4):784-792
The electrochemical and chemical oxidation of extended TTF 4 and 5 are analysed by cyclic voltammetry, Visible/NIR and ESR spectroscopies, and the X-ray structures of the new salts 5 x BF(4)(CH(2)Cl(2)) and 4 x ClO(4)(THF)(1/2) are presented. The effects of structural factors on the pi-dimerization or the disproportionation reaction of the cation radical are shown. The oxidation of compound 4 presents the successive formation of stable cation radical and dication species both in dichloromethane (DCM) and in a CH(3)CN/THF mixture. In contrast, for compound 5, the stability of the oxidation states strongly depends on the nature of the solvent. In DCM, the oxidation of 5 proceeds by two close one-electron transfers while in CH(3)CN/THF the dication is directly formed via a two-electron process. The X-ray structures of the two salts reveal the formation of pi-dimers of cation radical. While the dimer (5(2))(2+) is due mainly to pi-pi interactions between the conjugating spacer, the multiplication of the sulfur atoms in compound 4 contributes to stabilize the dimer by the combined effects of S-S and pi-pi interactions. Visible/NIR and ESR experiments confirm the higher tendency of 4(+)(.) to dimerize with the occurrence of dimer and monomer in solution, while for 5(+)(.) only the monomer is detected in DCM. On the other hand, by dissolution of 5 x BF(4)(CH(2)Cl(2)) in CH(3)CN, only the neutral and the dicationic states of compounds 5 are observed owing to the disproportionation reaction. 相似文献
76.
Beaudoin E Gourier C Hiorns RC François J 《Journal of colloid and interface science》2002,251(2):398-408
Hydrophobically modified poly(ethylene oxide), HMPEO, was studied in concentrated salt solutions. The influence of salts was compared to the effect of temperature on poly(ethylene oxide), PEO. As expected, the addition of monovalent cations (Na(+), K(+)) has the same effect as an increase in temperature in agreement with the thermodynamic properties of PEO: a decrease in solubility, micelle size, and viscosity was observed. Moreover, the intensity of neutron scattering peaks (characteristic of the semi-dilute solutions of these associative polymers) increases due to the collapse of PEO coronae in micelles. Very peculiar behavior was observed in the presence of divalent cations (Ca(2+), Mg(2+)): larger micelle aggregates and higher viscosities, relaxation times, and activation energies were observed by dynamic rheology. This behavior is attributed to interactions between divalent cations and oxygen in PEO backbones close to the micelle core, which may reinforce intermicellar bridges. 相似文献
77.
Cardinali F Mamlouk H Rio Y Armaroli N Nierengarten JF 《Chemical communications (Cambridge, England)》2004,(14):1582-1583
A multicomponent array made of a bis-copper(I) helicate core and two peripheral fullerene subunits has been prepared and electron transfer from the photoexcited Cu(I)-complexed unit to C60 occurs. 相似文献
78.
A pair of azo ligand complexes W(CO)5L (L = cis- or trans-azoisopropane) are reported in which ligand geometry is the only structural difference. The properties and particularly the difference in dynamical behavior of the complexes is disccused. 相似文献
79.
The 2-Phenyl-4,5-dimethylphosphorin P-W(CO)5 complex reacts easily as a dienophile with 2,3-dimethylbutadiene through its 1,6-positions and as a diene with N-phenylmaleimide, dimethyl acetylenedicarboxylate and cyclopentadiene, through its 1,4-positions. 相似文献
80.
Fernando J. S. Oliveira Francisca P. De França 《Applied biochemistry and biotechnology》2005,122(1-3):593-603
A 23 full factorial experimental design was adopted to estimate the effects of three variables on the biodegradation of oil during
soil bioremediation: bioaugmentation seeding a mixed culture, addition of fertilizer or mineral media, and correction of initial
pH of the soil to 7.0. The tests were carried out in polyvinyl chloride reactors with 5.0 kg of crude oil-contaminated soil
at 14 g/kg. After screening the variables, soil bioremediation tests were conduced with varied C:N ratios, yielding an increase
in biodegradation of the oil heavy fraction from 24 to 65%, consumption of total n-paraffins, and a remarkable decrease in the concentration of residual polycyclic aromatic hydrocarbons of the soil. 相似文献