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161.
Witek MA Wei S Vaidya B Adams AA Zhu L Stryjewski W McCarley RL Soper SA 《Lab on a chip》2004,4(5):464-472
Electrokinetic transport of Escherichia coli and Saccharomyces cerevisiae (baker's yeast) cells was evaluated in microfluidic devices fabricated in pristine and UV-modified poly(methyl methacrylate)(PMMA) and polycarbonate (PC). Chip-to-chip reproducibility of the cell's apparent mobilities (micro(app)) varied slightly with a RSD of approximately 10%. The highest micro(app) for baker's yeast cells was observed in UV-modified PC with 0.5 mM PBS (pH = 7.4), and the lowest was measured in pristine PMMA with 20 mM PBS (pH = 7.4). Baker's yeast in all devices migrated toward the cathode because of their smaller electrophoretic mobility compared to the EOF. In 0.5 mM and 1 mM PBS, E. coli cells migrated toward the anode in all cases, opposite to the direction of the EOF due to their larger electrophoretic mobility. E. coli cells in 20 mM PBS migrated toward the cathode, which indicated that the electrophoretic mobility of E. coli cells decreased at higher ionic strengths. Observed differential migrations of E. coli and baker's yeast cells in appropriately prepared polymer microchips were used as the basis for selective introduction into microfluidic devices of only one type of cell. As a working model, experiments were performed with E. coli and RBCs (red blood cells). RBCs migrated toward the cathode in pristine PMMA with 1 mM and 20 mM PBS (pH = 7.4), opposite to the direction of the E. coli cells. By judicious choice of the buffer concentration in which the cell suspension was prepared and the polymer material, RBCs or E. coli cells were selectively introduced into the microdevice, which was monitored via laser backscatter signals. 相似文献
162.
Francisco Radler de Aquino Neto Jari Nobrega Cardoso Alberto dos Santos Pereira Maria Conceiao Zupo Fernandes Carlos Alberto Caetano Andre Luiz de Castro Machado 《Journal of separation science》1994,17(4):259-263
HTHRGC was found essential for optimizing representative preparation of high molecular weight samples and enabling fingerprinting of heavy fractions of crude oils and associated paraffinic deposits in production pipelines. Laboratory experiments aimed at simulating the process of paraffin deposition could also be easily evaluated. A comparative investigation of the performance of cold on-column and SPI (PTV type) injectors, in conjunction with high temperature capillary columns, for analysis of high molecular weight fractions, was also conducted during the course of this work. 相似文献
163.
Buisson C Hebestreit M Weigert AP Heinrich K Fry H Flenker U Banneke S Prevost S Andre F Schaenzer W Houghton E Le Bizec B 《Journal of chromatography. A》2005,1093(1-2):69-80
The use of anabolic agents in food producing animals is prohibited within the EU since 1988 (96/22/EC directive). The control of the illegal use of natural steroid hormones in cattle is still an exciting analytical challenge as far as no definitive method and non-ambiguous analytical criteria are available. The ability of gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) to demonstrate the administration of 17beta-estradiol to bovine has been investigated in this paper. By comparison of 13C/12C isotopic ratio of main urinary estradiol metabolite, i.e. 17alpha-estradiol, with two endogenous reference compounds (ERCs), i.e. dehydroepiandrosterone (DHEA) and 5-androstene-3beta,17alpha-diol, the differentiation of estradiol metabolite origin, either endogenous or exogenous, has been proved to be achievable. After treatment, the delta(13)C(VPDB)-values of 17alpha-estradiol reached -27 per thousand to -29 per thousand, whereas delta13CVPDB-values of DHEA remained between -13 per thousand and -20 per thousand depending on the diet, maize and grass, respectively. A significant difference of delta13CVPDB between ERCs and 17alpha-estradiol was measurable over a period of 2 weeks after estradiol ester administration to the animal. 相似文献
164.
New multiresidue analytical method dedicated to trace level measurement of brominated flame retardants in human biological matrices 总被引:1,自引:0,他引:1
Cariou R Antignac JP Marchand P Berrebi A Zalko D Andre F Le Bizec B 《Journal of chromatography. A》2005,1100(2):144-152
A new method has been developed for the multi-residue measurement of the main brominated flame retardants (alpha- and gamma-hexabromocyclododecane (HBCD), tetrabromobisphenol A (TBBP-A) and polybrominated diphenyl ethers including decabromodiphenyl ether) in human biological matrices (serum, adipose tissue and breast milk). The proposed sample preparation procedure focused on reduced solvent and consumable consumption and associated procedural contamination, as well as reduced sample size. This protocol was fully validated and was proved to be suitable for identification of brominated flame retardant residues at ultra-trace level, as attested by preliminary results on real samples. 相似文献
165.
Aruna J. Weerasinghe Agozie N. Oyeamalu Fasil A. Abebe Andre R. Venter Ekkehard Sinn 《Journal of fluorescence》2016,26(3):891-898
Two novel sensors bearing rhodamine B and quinoline units have been synthesized. One of these, 1, allows sensitive and selective detection of Ni2+ and Cr3+ by forming non-fluorescent (1-Ni2+) and fluorescent (1-Cr3+) complexes respectively. Both metals trigger the formation of highly colored ring-open spirolactam. These form excellent probes for CN? which quenches the fluorescence of the 1-Cr3+ complex by extracting the Cr3+. Both Cr3+ and Cu2+ gave color changes with 2, but they are easily identified separately via the large fluorescence enhancement that occurs only with Cr3+. 相似文献
166.
We have developed a new method for the three-dimensional modeling of extended X-ray absorption fine structure (EXAFS) spectra
which enables the extraction of the local structure of aqueous metal complexes from spectral mixtures of several components.
The new method combines two techniques: Monte Carlo simulation and target transformation factor analysis (TFA). Monte Carlo
simulation is used to create random arrangements between the X-ray absorbing metal ion and the ligand atoms, and to calculate
the theoretical EXAFS spectrum of each arrangement. The theoretical EXAFS spectrum is then introduced as test spectrum in
the TFA procedure, to test whether or not the test spectrum is likely to be a component of the spectral mixtures. This coupled
procedure is repeated until the error in the test spectrum is minimized. The new method can thus be used to isolate and refine
the structure of complexes from spectral mixtures and to determine their relative concentrations, solely on the basis of an
estimate of a ligand structure. The performance of the proposed method is validated using uranium Liii-edge EXAFS spectra
of binary mixtures of two uranium(VI) 3,4-dihydroxybenzoic acid complexes. 相似文献
167.
Alexander V. Yakimansky Stanislav V. Bushin Marina A. Bezrukova Alexey A. Lezov Alexander S. Gubarev Elena V. Lebedeva Lilija I. Akhmadeeva Anna N. Podseval'nikova Nikolaj V. Tsvetkov Guy Koeckelberghs Andre Persoons 《Journal of Polymer Science.Polymer Physics》2016,54(9):875-883
Conducting polymers demonstrate low solubility in organic solvents. Introducing aliphatic substituents into polymer chains improves their solubility, but may also lead to changes in conformational characteristics of macromolecules. In the present work, the studies of hydrodynamic properties and conformational characteristics of comb‐shaped poly(3‐hexylthiophene) with aliphatic side substituents were carried out in chloroform solutions. Conformational analysis of the studied macromolecules was performed for the first time using homologous series with a wide range of molecular weights of the polymers in dilute solutions. The hydrodynamic properties of these macromolecules were interpreted using the worm‐like spherocylinder model and the straight spherocylinder model. The projection of the monomer unit in the direction of the main polymer chain λ = 0.37 nm was determined experimentally. The following parameters of poly(3‐hexylthiophene) were characterized and quantified: equilibrium rigidity (Kuhn segment length) А = 6.7 nm and hydrodynamic diameter of a polymer chain d = 0.6 nm. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 875–883 相似文献
168.
Two distinct preparations of amphiphilic diblock copolymer vesicles (i.e. polymersomes), composed of (poly(ethylene oxide)-poly(butadiene)) (PEO-PBD), with molecular weights of 1.8 kDa and 10.4 kDa, offering different hydrophobic membrane thicknesses, were used to encapsulate the oxygen (O(2)) storage and transport protein hemoglobin (Hb) for possible application as a red blood cell (RBC) substitute. Key biophysical properties as well as the kinetics of polymersome encapsulated Hb (PEH) interaction with physiologically important gaseous ligands (O(2), carbon monoxide and nitric oxide) were measured as a function of the hydrophobic membrane thickness of the PEH particle. Taken together, the results of this work show that PEHs exhibit biophysical properties and retarded ligand binding/release kinetics (compared to cell-free Hb), which are similar to the behavior of RBCs. Therefore, PEHs have the potential to serve as safe and efficacious RBC substitutes for use in transfusion medicine. 相似文献
169.
Martin Schmid Andre Kaftan Hans-Peter Steinrück J. Michael Gottfried 《Surface science》2012,606(11-12):945-949
The electronic states of submonolayers and multilayers of cobalt(II) phthalocyanine (CoPc) adsorbed on Ag(111) were examined with photoelectron spectroscopy to obtain insight into the details of the substrate–adsorbate interaction. UV photoelectron spectroscopy (UPS) reveals the presence of two interaction-related valence states in the direct vicinity of the Fermi edge, in agreement with previous DFT calculations. X-ray photoelectron spectra indicate that the substrate–adsorbate interaction results in transfer of electron density from the substrate to the Co(II) ion. Substantial changes in the Co 2p multiplet structure, a spectral pattern induced by the open-shell character of the central Co(II) ion, indicate a complete quenching of the molecular spin. While pristine CoPc molecules are paramagnetic with S = 1/2, molecules in direct contact to the Ag(111) substrate appear to be in a diamagnetic state. 相似文献
170.
Bertrand Vivet Florine Cavelier Jean Martinez Claude Didierjean Michel Marraud Andre Aubry 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(12):1452-1454
The silaproline‐containing dipeptide N‐(3,3‐dimethyl‐1‐pivaloyl‐1‐aza‐3‐sila‐5‐cyclopentylcarbonyl)‐l ‐alanine isopropylamide, C17H33N3O3Si, has two independent molecules in the asymmetric unit and each adopts a β‐II folded conformation, where the amide on the terminal C interacts intramolecularly with the pivaloyl O atom. The five‐membered silaproline ring is Cβ‐puckered, an infrequent conformation for the homologous proline ring. 相似文献