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51.
The determination of sulphide at an electrochemically generated nickel oxide layer at glassy carbon and screen-printed electrodes in acidic media has been examined and appraised. The NiO layer was found to produce a stripping-like signal to sulphide and gave a linear peak current response from 20 to 90 μM. The response was further enhanced by repetitive cycling allowing accumulation of nickel sulphide at the electrode surface such that lower micromolar levels of sulphide (i.e. 5 μM) can be determined. The response at the NiO layer to sulphide is shown to be reproducible over a period of 24 h, thereby offering the development of a disposable amperometric sensor for sulphide. 相似文献
52.
A new photoelectron spectroscopic method is described directed towards the measurement of the photoelectron spectra of trapped ions. An electrostatic retarding field electron energy analyser incorporating a channel plate is included with an ion trap in a strong magnetic field. The form of photoelectron spectrum is shown to be strongly influenced by a elastic scattering effects which can be enhanced by using an electron trapping potential well. The resultant spectra then have a particularly simple and useful form. 相似文献
53.
Lithium reductions of 7-chloronorbornadiene and of bis(7-norbornadienyl)mercury both provide (C7H7)2Li2 ( 5a ). This product is accompanied by C7H7Li2Cl ( 5c ) in the first case, and by C7H7Li ( 5b ) in the second. The theoretically anticipated properties of all three organolithiums are apparent in the consistent Cs symmetry of their hydrocarbon ligands, their protolytic destruction by 12-crown-4, and their significant J(C(7), Li) ( 5a , 7.6; 5b , 16.0; 5c 8.9 Hz). 相似文献
54.
Jo E Sanna MG Gonzalez-Cabrera PJ Thangada S Tigyi G Osborne DA Hla T Parrill AL Rosen H 《Chemistry & biology》2005,12(6):703-715
The essential role of the sphingosine 1-phosphate (S1P) receptor S1P(1) in regulating lymphocyte trafficking was demonstrated with the S1P(1)-selective nanomolar agonist, SEW2871. Despite its lack of charged headgroup, the tetraaromatic compound SEW2871 binds and activates S1P(1) through a combination of hydrophobic and ion-dipole interactions. Both S1P and SEW2871 activated ERK, Akt, and Rac signaling pathways and induced S1P(1) internalization and recycling, unlike FTY720-phosphate, which induces receptor degradation. Agonism with receptor recycling is sufficient for alteration of lymphocyte trafficking by S1P and SEW2871. S1P(1) modeling and mutagenesis studies revealed that residues binding the S1P headgroup are required for kinase activation by both S1P and SEW2871. Therefore, SEW2871 recapitulates the action of S1P in all the signaling pathways examined and overlaps in interactions with key headgroup binding receptor residues, presumably replacing salt-bridge interactions with ion-dipole interactions. 相似文献
55.
A nickel-catalyzed method for the three-component coupling of alkenes (ethylene and alpha olefins), aldehydes, and silyl triflates is described, and this process represents the first catalytic method for coupling aldehydes and alkenes to give allylic alcohol derivatives. Conceptually, the alkene functions as a replacement for an alkenylmetal reagent. 相似文献
56.
Using a modified photoelectron spectrometer the radiative lifetimes of some electronically excited diatomic and triatomic molecular ions have been determined. The method is based on measuring the time delay between the ejection of a photoelectron from a molecule and the emission of a photon from the resulting ion. 相似文献
57.
A rapid and easy route to formamides by microwave assisted N-formylation of primary and secondary amines is described. Using an insoluble polymer or an inorganic solid-supported reagent as a formylating agent, microwave irradiation furnished the corresponding formamides in high yields, with reduced reaction time and solvent volume over the conventional approach. 相似文献
58.
Wender PA Baryza JL Bennett CE Bi FC Brenner SE Clarke MO Horan JC Kan C Lacôte E Lippa B Nell PG Turner TM 《Journal of the American Chemical Society》2002,124(46):13648-13649
Macrocycle 1 is a new highly potent analogue of bryostatin 1, a promising anti-cancer agent currently in human clinical trials. In vitro, 1 displays picomolar affinity for PKC and exhibits over 100-fold greater potency than bryostatin 1 when tested against various human cancer cell lines. Macrocycle 1 can be generated in clinically required amounts by chemical synthesis in only 19 steps (LLS) and represents a new clinical lead for the treatment of cancer. 相似文献
59.
The products of the reaction of butadiene with diethyl malonate catalysed by a palladium complex and of butadiene with acetaldehyde catalysed by a nickel(0) complex have been used in two syntheses of 3,7-dimethylpentadecan-2-ol. 相似文献
60.
A detector for HPLC is based on suppression of chemiluminescence from the Cu(II)-luminol-peroxide reaction. Analytes which complex Cu(II) reduce the free Cu(II) concentration and thus the observed chemiluminescence intensity. The degree of chemiluminescence suppression is a measure of the analyte concentrations. Detection limits are in the range of 1 pmole-1 nmole for amino acids (both primary and secondary without derivatization), CN–, amines, catecholamines, catechol, and aminoglycoside antibiotics. The detection approach is demonstrated with an ion-exchange separation of amino acids, a reverse phase separation of catecholamines, and an ion-pair separation of the three components of gentamicin C in commercial gentamicin sulfate. 相似文献