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排序方式: 共有263条查询结果,搜索用时 779 毫秒
61.
A versatile method for direct, covalent attachment of DNA microarrays at silicon nitride layers, previously deposited by chemical vapor deposition at silicon wafer substrates, is reported. Each microarray fabrication process step, from silicon nitride substrate deposition, surface cleaning, amino-silanation, and attachment of a homobifunctional cross-linking molecule to covalent immobilization of probe oligonucleotides, is defined, characterized, and optimized to yield consistent probe microarray quality, homogeneity, and probe-target hybridization performance. The developed microarray fabrication methodology provides excellent (high signal-to-background ratio) and reproducible responsivity to target oligonucleotide hybridization with a rugged chemical stability that permits exposure of arrays to stringent pre- and posthybridization wash conditions through many sustained cycles of reuse. Overall, the achieved performance features compare very favorably with those of more mature glass based microarrays. It is proposed that this DNA microarray fabrication strategy has the potential to provide a viable route toward the successful realization of future integrated DNA biochips. 相似文献
62.
We present autocorrelation measurements showing the high-speed sampling and switching capabilities of SOS photoconducting elements which have been ion implanted with 60 and 160 keV Si28 ions. An analysis of the circuit shows the intrinsic photoconductive decay to be very fast (3.5 ps) and that the measured response is primarily limited by the gap capacitance and the associated R-C time. 相似文献
63.
Thomas J. Manning 《光谱学快报》2013,46(5):959-965
Abstract The Re I (527. 55 nm, 18955 cm?1) emission line from a hollow cathode lamp (HCL) is proposed as a standard for wavenumber accuracy and precision, resolution accuracy and precision and intensity precision. The Los Alamos Fourier transform spectrometer measured the HCL emission at high resolution (0. 026 cm?1). The advantages of this spectral line to other emission standards is discussed. 相似文献
64.
Dewei Tang Jason R. Buck Matthew R. Hight H. Charles Manning 《Tetrahedron letters》2010,51(35):4595-4016
We herein report a dramatically improved total synthesis of the high-affinity translocator protein (TSPO) ligand DPA-714, featuring microwave-assisted organic synthesis (MAOS). Compared with previously described approaches, our novel MAOS method dramatically reduces overall reaction time without adversely effecting reaction yields. We envision that the described MAOS protocol may be suitably applied to high-throughput, diversity-oriented synthesis of novel compounds based on the pyrazolo-pyrimidinyl scaffold. Such an approach could accelerate the development of focused libraries of novel TSPO ligands with potential for future development as molecular imaging and therapeutic agents. 相似文献
65.
Tyrosine ammonia-lyase (TAL) is a recently described member of the aromatic amino acid lyase family, which also includes phenylalanine (PAL) and histidine ammonia-lyases (HAL). TAL is highly selective for L-tyrosine, and synthesizes 4-coumaric acid as a protein cofactor or antibiotic precursor in microorganisms. In this report, we identify a single active site residue important for substrate selection in this enzyme family. Replacing the active site residue His89 with Phe in TAL completely switched its substrate selectivity from tyrosine to phenylalanine, thereby converting it into a highly active PAL. When a corresponding mutation was made in PAL, the enzyme lost PAL activity and gained TAL activity. The discovered substrate selectivity switch is a rare example of a complete alteration of substrate specificity by a single point mutation. We also show that the identity of the amino acid at the switch position can serve as a guide to predict substrate specificities of annotated aromatic amino acid lyases in genome sequences. 相似文献
66.
Reily MD Robosky LC Manning ML Butler A Baker JD Winters RT 《Journal of the American Chemical Society》2006,128(38):12360-12361
A new NMR chemical shift standard and pH indicator, difluorotrimethylsilanylphosphonic acid (DFTMP), is described, and the utility of this reagent is demonstrated for in situ determination of pH in complex biofluids. The pH dependence of this reagent allows accurate in situ determination of aqueous solution pH to within an RMSE of 0.02 pH units over a pH range of 5 to 8. Advantages of this reagent over previously described pH-sensitive components include (1) lack of metal binding affinity, (2) minimal disturbance of endogenous spectral regions, and (3) the potential to function as a multinuclear pH indicator and chemical shift reference point for 19F, 1H, and 31P nuclei. This reagent will be generally useful for NMR experiments on biological systems where the pH needs to be accurately measured at the moment of data acquisition. 相似文献
67.
A method is described for the asymmetric synthesis of 4-substituted indoles from the Rh2(S-DOSP)4-catalyzed decomposition of vinyldiazoacetates in the presence of N-Boc-4-acetoxy-6,7-dihydroindole. The reaction proceeds via a combined C-H activation/Cope rearrangement-elimination mechanism resulting in good yields and very high asymmetric induction. 相似文献
68.
R. J. Manning und M. Nierenstein 《Fresenius' Journal of Analytical Chemistry》1914,53(8):521-522
Ohne Zusammenfassung 相似文献
69.
Partha S. Ray Joan Buote Charles A. Webster Michael J. Manning 《Journal of heterocyclic chemistry》1993,30(1):45-48
Synthesis of pyridazino[1,2-a][1,2,4]benzotriazin-6-one derivatives involving reaction of either 1,2,3,6-tetra-hydropyridazine ( 9 ) or hexahydropyridazine 14 with 2-fluoro-5-nitrophenylisocyanate ( 5 ) to give, via intramolecular cyclization, 3a and 16 respectively is described. Compound 3a was converted to 18 via methylation and hydroxylation to give 20 followed by conversion to the acetonide derivative 18 . Both 16 and 18 were reduced to the amino derivatives 17 and 19 respectively. 相似文献
70.
Thomas J. Manning Brian Little Jerry Purcell Amy Feldman William Parker Katrice Register Brandy Sumner Clint Schibner 《The Chemical Educator》2002,7(5):278-283
The goal of this paper is to provide data that can be used in a variety of exercises ranging from kinetics in general chemistry to advanced problems in physical chemistry. The data provided relates to ozone-decay kinetics in various atmospheres (O2, N2, Ar) as measured by ultraviolet/visible absorbance spectroscopy (UV/vis) at 254 nm. The absorbance of ozone is monitored over a 75-min time period, and by using Beers law the concentration is calculated. Nine data sets, each repeated three times, of absorbance measurements are provided for student exercises, and prelaboratory and postlaboratory questions are suggested. 相似文献