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排序方式: 共有162条查询结果,搜索用时 15 毫秒
71.
Casper D Becker-Szendy R Bratton CB Cady DR Claus R Dye ST Gajewski W Goldhaber M Haines TJ Halverson PG Jones TW Kielczewska D Kropp WR Learned JG LoSecco JM McGrew C Matsuno S Matthews J Mudan MS Price L Reines F Schultz J Sinclair D Sobel HW Stone JL Sulak LR Svoboda R Thornton G van der Velde JC 《Physical review letters》1991,66(20):2561-2564
72.
Thorslund S Sanchez J Larsson R Nikolajeff F Bergquist J 《Colloids and surfaces. B, Biointerfaces》2005,46(4):240-247
A new composition of heparin coating for microfluidic systems made out of poly(dimethylsiloxane) (PDMS) was developed and evaluated. The coating that consists of a conditioning polyamine layer followed by two heparin/glutaraldehyde layers, resulted in channel surfaces with sufficient wettability to obtain flow of human normal plasma by capillary force alone. Hydrophilic channel walls are a desirable characteristic in microfluidic devices, since alternative pumping mechanisms must otherwise be included into the system. The immobilized heparin showed high antithrombin-binding capacity and a low degree of blood–material interaction. Plasma in contact with heparin-coated PDMS formed no detectable fibrin in a spectrophotometric assay by which plasma in contact with non-treated PDMS showed complete coagulation. The quartz crystal microbalance technique with energy dissipation monitoring (QCM-D) was utilized to obtain detailed information regarding adsorption kinetics and structural properties of the different layers composing the heparin coating. 相似文献
73.
A novel method for the manufacturing of microchips for on-chip combinations of electrochemistry (EC) and sheathless electrospray ionisation mass spectrometry (ESI-MS) is described. The technique, which does not require access to clean-room facilities, is based on the incorporation of an array of gold microcoil electrodes into a poly(dimethylsiloxane)(PDMS) microflow channel equipped with an integrated graphite based sheathless ESI emitter. Electrochemical measurements, which were employed to determine the electroactive area of the electrodes and to test the microchips, show that the manufacturing process was reproducible and that the important interelectrode distance in the electrochemical cell could to be adequately controlled. The EC-ESI-MS device was evaluated based on the ESI-MS detection of the oxidation products of dopamine. The results demonstrate that the present on-chip approach enables full potentiostatic control of the electrochemical cell and the attainment of very short transfer times between the electrochemical cell and the electrospray emitter. The transfer times were 0.6 and 1.2 s for flow rates of 1.0 and 0.5 microL min(-1), respectively, while the electrochemical conversion efficiency of the electrochemical cell was found to be 30% at a flow rate of 0.5 microL min(-1). To decouple the electrochemical cell from the ESI-MS high voltage and to increase the user-friendliness, the on-line electrochemistry-ESI-MS experiments were performed using a wireless Bluetooth battery-powered instrument with the chip floating at the potential induced by the ESI high voltage. The described on-chip EC-ESI-MS device can be used for fundamental electrochemical investigations as well as for applications based on the use of electrochemically controlled sample pretreatment, preconcentration and ionisation steps prior to ESI-MS. 相似文献
74.
Zuberovic A Ullsten S Hellman U Markides KE Bergquist J 《Rapid communications in mass spectrometry : RCM》2004,18(23):2946-2952
Capillary electrophoresis (CE) was coupled off-line with matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOFMS) for the analysis of proteins and peptides. CE fractions were collected directly on a matrix-coated MALDI target, using a sheath-flow interface. Protein adsorption during CE separations was prevented by coating the capillaries with the physically adsorbed, cationic polymer PolyE-323. The CE/MALDI-MS system was used for the analysis of model proteins and peptides at physiological pH as well as analysis of proteins in tear fluid. Moreover, tryptic on-target digestion of the collected protein fractions, with subsequent MALDI-MS and MS/MS peptide analysis, was demonstrated. 相似文献
75.
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78.
Bazoti FN Bergquist J Markides K Tsarbopoulos A 《Journal of the American Society for Mass Spectrometry》2008,19(8):1078-1085
Abnormal accumulation and aggregation of amyloid-beta-peptide (Abeta) eventually lead to the formation and cerebral deposition of amyloid plaques, the major pathological hallmark in Alzheimer's disease (AD). Oleuropein (OE), an Olea europaea L. derived polyphenol, exhibits a broad range of pharmacological properties, such as antioxidant, anti-inflammatory, and antiatherogenic, which could serve as combative mechanisms against several reported pathways involved in the pathophysiology of AD. The reported noncovalent interaction between Abeta and OE could imply a potential antiamyloidogenic role of the latter on the former via stabilization of its structure and prevention of the adaptation of a toxic beta-sheet conformation. The established beta-sheet conformation of the Abeta hydrophobic carboxy-terminal region and the dependence of its toxicity and aggregational propensity on its secondary structure make the determination of the binding site between Abeta and OE highly important for assessing the role of the interaction. In this study, two different proteolytic digestion protocols, in conjunction with high-sensitivity electrospray ionization mass spectrometric analysis of the resulting peptide fragments, were used to determine the noncovalent binding site of OE on Abeta and revealed the critical regions for the interaction. 相似文献
79.
Karthikeyan Gunasekaran Peter L. Bergquist Anwar Sunna 《Applied biochemistry and biotechnology》2013,169(2):651-659
We describe an improved method for the production of recombinant Qβ replicase heterotetramer. The successful expression of the soluble Qβ RNA polymerase complex depends on the EF-Ts and EF-Tu subunits being co-expressed prior to β-subunit expression. Efficient co-expression requires two different inducible operons to co-ordinate the expression of the heterotrimer. The complete heterotetramer enzyme complex is achieved by production of the recombinant S1-subunit of Qβ replicase in a separate host. This approach represents a facile way for producing and purifying large amounts of soluble and active recombinant Qβ replicase tetramer without the necessity of a His-tag for purification. 相似文献
80.
Thioaurones are converted to a mixture of thiaindenes and thioflavonols when exposed to reaction conditions employed in SPPS, that is, treatment with trifluoroacetic acid in the presence of triethylsilane. 相似文献