The results of a series of investigations dealing with the development of enzymatic methods for determination of biologically
active compounds, viz., inhibitors, activators, and substrates of native and immobilized enzymes of the oxidoreductase (peroxidases, alcohol dehydrogenases)
and hydrolase (alkaline and acid phosphatases) classes isolated from diverse sources are summarized. Novel original approaches,
proposed by the authors, for improving the sensitivity, selectivity, and rapidity of the methods are discussed. Numerous examples
of application of the developed enzymatic procedures for the analysis of a wide range of samples are given.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 583–597, April, 2007. 相似文献
Transparent and flexible carbon doped ZnO (C:ZnO) field emission device was successfully fabricated on an arylite substrate. Excellent adhesion of deposited C:ZnO on the flexible substrate was achieved with low sputtering power and Ar flow rate. In the fabricated device, nanostructured C:ZnO and as‐deposited thin films were used as field emitter and phosphor screen, respectively. The C:ZnO thin film showed a transparency of about 80% at 550 nm wavelength and average sheet resistance of 1.96 kΩ/□. The C:ZnO phosphor screen emitted red light during the field emission measurement, correlating the dominant cathodoluminescence peak at 646 nm. Thus, a promising transparent and flexible field emission display can be realized with C:ZnO based material.
Transparent and flexible C:ZnO film phosphor screen (anode) and nanocone emitters (cathode) for field emission device. 相似文献
The rapid detection of Listeria monocytogenes contamination in food is essential to prevent food-borne illness in humans. The aim of this study was to differentiate non-contaminated milk from milk contaminated with L. monocytogenes using enzyme substrates coupled with the analysis of volatile organic compounds (VOCs). The method is based on the activity of β-glucosidase and hippuricase enzymes and the detection of a specific VOC i.e. 2-nitrophenol and 3-fluoroaniline, respectively. VOCs were extracted, separated and detected by headspace-solid phase microextraction coupled to gas chromatography–mass spectrometry (HS-SPME GC–MS). This approach required the inclusion of the selective agent's cycloheximide, nalidixic acid and acriflavine HCl in the growth medium to inhibit interfering bacteria. The VOCs were liberated by L. monocytogenes provided that samples contained at least 1–1.5 × 102 CFU ml−1 of milk prior to overnight incubation. This approach shows potential for future development as a rapid method for the detection of L. monocytogenes contaminated milk. 相似文献
The influence of mechanical contortion upon the electrochemical performance of screen‐printed graphite paper‐based electroanalytical sensing platforms is evaluated and contrasted with traditionally employed polymeric based screen‐printed graphite sensors. Such a situation of implementation can be envisaged for the potential sensing of analytes on the skin where such sensors are based, for example in clothing where mechanical contortion, viz, bending will occur, and as such, its effect upon electrochemical sensors is of both fundamental and applied importance. The effect of mechanical contortion or stress upon electrochemical behaviour and performance is of screen printed sensors is explored. Comparisons are made between both paper‐ and polymeric‐ based sensing platforms that are evaluated towards the sensing of the well characterised electrochemical probes potassium ferrocyanide(II), hexaammine‐ruthenium(III) chloride and nicotinamide adenine dinucleotide (NADH). It is determined that the paper‐based sensors offer greater resilience in terms of electrochemical performance after mechanical stress. We gain insights into the role played by both the effect of the time of mechanical contortion and additionally the potentially detrimental effects of repeated contortion are explored. These unique paper‐based sensors hold promise for widespread applications where flexible and ultra‐low cost sensors are required such as applications into medical devices were ultra‐low cost sensors are a pre‐requisite, but also for utilisation within applications which require the implementation of ultra‐flexible electroanalytical sensing platforms such as in the case of wearable sensors, whilst maintaining useful electrochemical performances. 相似文献
Allylic alcohols, rather than halides, acetates, or carbonates can be used directly in the Friedel–Crafts‐type coupling with various phenols. The use of a RuIV, rather than a RuII, precursor promotes the formation of one H+ per cycle so that a large excess of acid is never present in the reaction mixture. Consequently, the leaving group in the oxidative addition reaction is H2O, thereby avoiding the production of an unnecessary by‐product. 相似文献
Polycrystalline ZnO films with good orientation were deposited on sapphire, quartz, Si and 7059 glass substrates by r.f. magnetron sputtering. A strong UV photoluminescence (PL) peak (located at 356 nm) and a weak blue emission peak (located at 446 nm) were observed at room temperature (RT) for the films deposited on sapphire, quartz and Si substrates when excited with 270 nm light. For the films prepared on Corning 7059 glass, only a strong 446 nm blue emission peak was found, and the PL intensity decreased with increasing oxygen pressure during films deposition. The intensity of the UV emission increased 7 and 14 times, respectively, for the films on sapphire and quartz substrates after high temperature annealing in vacuum. The UV emission originates from the inter-band transition of electrons and the blue emission is due to transition of electrons from the shallow donor level of the oxygen vacancies to the valence band. 相似文献