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41.
Jiaming L Wenqi L Xuelin L Hailing C Qiaomei L Longdi L Zhimin L Guohui Z Cuilian C 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(13-14):3077-3081
Luminescent particles of lead carboxymethyl cellulose (Pb(CMC)2) containing salicyl fluorones (THBF), Pb(CMC)2-THBF were synthesized by the sol-gel method, using sodium carboxymethyl cellulose (NaCMC) as precursor and Pb2+ as precipitant. Pb(CMC)2-THBF can emit the intense and stable solid substrate room temperature phosphorescence (SS-RTP) on filter paper. And EDTA can chelate Pb2+ in Pb(CMC)2-THBF, causing it to decompose into aqueous soluble components PbY2-, CMC- and THBF, which can react with Ag+ to form Ag(CMC)2-THBF, causing the decrease of phosphorescence intensity. Based on the facts above, a new method for the determination of trace silver by SS-RTP quenching method was established. The linear range of this method is 8.0-40.0 fg spot(-1) (20.0-100.0 pg ml(-1)), with a detection limit (LD) of 2.2 fg spot(-1) (corresponding to a concentration range of 5.5 x 10(-13) g ml(-1)), and the regression equation of working curve is DeltaI(p) = 12.56 + 0.5527C(Ag+) (fg spot(-1), 0.4 microl spot(-1)), n = 8, r = 0.9992. This method has been applied to the determination of trace silver in human hair and tea sample with satisfactory results. The mechanism of SS-RTP emission is also discussed. 相似文献
42.
A starter culture ofTrichoderma reesei (Rut-C30) prepared in a liquid fluidized bed reactor (LFBR) gave better growth and greater cellulase production in submerged
fermentation than a conventional shake flask inoculum. The LFBR starter was prepared by first coatingT. reesei spores to 0.25 mm size corncob (1.0x108g-1) in a medium containing 1.0% corncob, 0.5 gL-1 xylose and 0.1 gL-1 lactose in a balanced salt solution, then fluidizing the particles in the LFBR for 36 h to allow germination of the spores,
and covering the particles with an approx 30 μm thick biofilm. This biofilm that developed in constant adherence to the lignocellulosic
carrier, apparently became well adapted to grow rapidly on insoluble cellulose substrates (Solca Floc), and had the enzymes
of the cellulase complex induced for increased cellulase production.
The LFBR starter used in a stirred tank reactor (STR) gave 15 gL-1 biomass production and 6.5 IU mL-1 overall cellulase activity with a volumetric productivity of 64 IU L-1h-1 in a 5 d fermentation, compared with a 7 d shake flask inoculum that gave 11 gL-1 biomass and 3.2 IU mL-1 cellulase activity, with a volumetric productivity of 31IU L-1h-1. The LFBR starter culture retained its viability in dry storage for 6–9 mo. 相似文献
43.
A novel electroless deposition method for depositing highly uniform adhesive thin films of copper selenide (Cu3Se2) on silicon substrates from aqueous solutions is described. The deposition is carried out by two coupled galvanic reactions in a single deposition bath containing copper cations, hydrogen fluoride, and selenous acid: the galvanic deposition of copper on silicon and the subsequent galvanic reaction between the deposited copper with selenous acid in the deposition bath. The powder X-ray diffraction and scanning electron microscopy are used to characterize and examine the deposited films. 相似文献
44.
《Journal of separation science》2003,26(17):1509-1519
Theophylline, tolbutamide, mephenytoin, debrisoquin, and dapsone are marker substrates for CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4, respectively. A silica‐based monolithic column (Chromolith SpeedROD RP‐18e, 50×4.6 mm) was used to separate these five marker substrates of cytochrome P450 within only 84 s. Linear gradient elution was from acetonitrile‐water‐formic acid (10 : 90 : 1, v/v/v) to acetonitrile‐water‐formic acid (90 : 10 : 1, v/v/v) in 1.4 min. The flow rate was 2.5 mL/min. The retention time was 0.52 min for theophylline, 0.67 min for debrisoquin, 0.78 min for dapsone, 0.96 min for mephenytoin, and 1.13 min for tolbutamide. Detection was by tandem mass spectrometry using a PE Sciex API 3000 mass spectrometer with a Turbo‐Ionspray source in positive mode. A simple protein precipitation method was used. This method was validated over the concentration range of 5–2000 ng/mL based on the sample volume of 0.1 mL. 相似文献
45.
46.
A novel, sensitive method for detecting protease inhibitors by using fluorescent protease substrates in gels is described. The protease inhibitors were separated on sodium dodecyl sulfate (SDS)-polyacrylamide gels containing a copolymerized peptide substrate, namely 4-methyl-coumaryl-7-amide (MCA). As the incorporated substrates in the gel, Boc-Phe Ser-Arg-MCA was used for trypsin, Suc-Ala-Ala-Pro-Phe-MCA for alpha-chymotrypsin, and Z-Phe-Arg-MCA for papain. After electrophoresis, washing and incubating the gel with the target protease solutions allowed the substrate to be cleaved by the protease, and the release of the fluorescent 7 amino-4 methyl-coumarin (AMC), which was detected under a UV transilluminator. The uncleaved peptide-MCA substrate remained where the inhibitors were present, and was visualized as dark blue bands on the light-green fluorescent background gel. This new method offers several advantages over other previous methods including: (i) greatly increased sensitivity can be achieved in a shorter period of time, which may be useful for discovering new protease inhibitors in small amounts of crude material; (ii) the procedure is quite simple and quick since the incubation period is very short and no time is needed for staining and destaining steps; (iii) since these probes using substrate specificity/target proteases, they are excellent tools for detection and discrimination of unknown protease inhibitors for various target proteases. 相似文献
47.
48.
Data on the kinetics, selectivity, kinetic isotope effect, and the effect of the acidity of the medium on the rate of the
reactions of benzene and alkylbenzenes in sulfuric acid (59–78 wt.% H2SO4) solutions of 1-adamantanol at 30 °C indicate that the direct reagents are the adamantyl carbocations (Ad+) that alkylate the arenes. The ortho positions of the benzene ring are not accessible on account of steric hindrances. The
rate of attack by the Ad+ cation on the accessible para and meta positions of the ring is controlled by the formation of a σ complex.
__________
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 1, pp. 14–18, January–February, 2006. 相似文献
49.
50.
Fractal dimension of a carious tooth surface was determined using an electrochemical method. The method was based on time-dependent diffusion towards electrode surfaces, which is one of the most useful and reliable methods for the determination of fractal dimension of electrode surfaces. For this purpose, the tooth was covered with a gold layer, which acted as an electrode in electrochemical experiments. It is suggested that the fractal dimension can be used as a quantitative measure of the state of dental surfaces. The method presented demonstrates the power of electrochemical techniques for the determination of fractal dimension of surface of non-conducting objects. 相似文献