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1.
A new sensor for NADH was developed by making use of an immobilized subcellular organelle. Mitochondria was used as a model system for assembling an organelle sensor. Mitochondrial electron transport particles (ETP) were prepared from beef heart muscle and entrapped in the membrane formed of agar gel. The membrane-bound ETP was found capable of NADH oxidation: $$NADH + \tfrac{1}{2}O_2 + H^ + \xrightarrow{{ETP}}NAD^ - + H_2 O$$ The membrane was tightly attached to the surface of an oxygen electrode capable of amperometric detection of O2. The sensor responded to NADH in solution with a resulting electric output. The response was enhanced by the addition of 2,4-dinitrophenol (DNP). NADH was determined in the concentration range 1–300 µM. NADH was alternatively determined for 2 weeks without replacing the ETP-bound membrane.  相似文献   

2.
A new AMP derivative substituted with spacer arms both at position N6 and C8 of the adenine moiety was synthesized and immobilized to Sepharose. To the immobilized ligand was subsequently coupled C8-substituted ATP in a solid-phase synthesis fashion yielding the bifunctional general ligand AMP-ATP. This affinity material was used in the separation of two major groups of enzymes, dehydrogenases and kinases. It was found that on passage of crude homogenates obtained from mouse kidney through the affinity column, several dehydrogenases and kinases were bound, which could be eluted separately using pulses of NADH and ATP, respectively. In the fractions obtained on NADH elution, lactate dehydrogenase, malate dehydrogenase, and α-glycerol phosphate dehydrogenase were found, whereas ATP eluted 3-phosphoglyceric acid kinase, pyruvate kinase, and aldolase.  相似文献   

3.
The action of phospholipase D on rat liver mitochondria in the presence of methanol, glycerol, and ethanolamine has been studied. The phospholipid compositions of the modified and native mitochondria have been determined. Incubation of the mitochondria with phospholipase D led to a considerable decrease in the activities of cytochrome c oxidase and NADH-cytochrome reductase.  相似文献   

4.
The chemical characterization of horse liver alcohol dehydrogenase solubilized in isooctane via reverse micelles formed by the anionic surfactant di (2-ethyl-hexyl) sodium sulfosuccinate (AOT) and water (0.6 to 4% v/v) is presented. The enzyme’s catalytic activity toward acetaldehyde reduction is markedly dependent upon w0 = [H2O]/[AOT], and upon the pH of the stock aqueous solution (pHst), from which the hydrocarbon enzyme solution is prepared. Kinetically, the micellar solution appears to follow a normal Michaelis-Menten behavior, with a turnover number which, under the optimal conditions (w0 = 42, pHst = 8.8), appears to be higher than in bulk water. The affinity between enzyme and NADH, as judged from direct binding studies (quenching of the protein fluorescence), is much reduced with respect to water if concentrations refer to the water pool of the micelles, and comparable to water if concentrations refer to the overall volume (hydrocarbon plus water pool). Also, the Km values are much higher if concentrations refer to the water pool. Ultraviolet absorption studies show that the aromatic chromophores are not significantly perturbed on going from a water solution to the micellar solution. The essentially aqueous environment of the protein in the reverse micelles is confirmed by fluoresence studies. Circular dichroism studies show that the enzyme’s conformation in the micelles is similar to that in water; however, under certain conditions, small but significant changes of the main chain folding seem to occur, which do not impair enzymatic activity. The spectroscopic properties of NADH in the hydrocarbon phase (fluorescence and circular dichroism) are also investigated. The potential of the LADH-NADH system for technical applications (oxidoreduction of lipophylic substrates) is discussed.  相似文献   

5.
The dissociation energy of the C2H4 · HCl van der Waals complex was determined to be 3.18±0.73 kcal mol?1 by a dissociative photoionization technique. C2H4 · HCl was produced by free expansion of a 1:4 mixture of C2H4 in HCl and the clusters were ionized with tunable synchrotron radiation. The photoionization efficiency function of (C2H4 · HCl)+ from C2H4 · HCl was determined between 600 and 1,300 Å and the onset for (C2H4 · HCl)+ was established as 1,163±2 Å = 10.66±0.02 eV; these values give ΔH f 0 (C2H4 · HCl) = ?10.7±0.7 kcal mol?1 and ΔH f 0 (C2H4·HCl+)=235.1±0.9 kcal mol?1. A complex ion dissociation energyD 0(C2H4 · HCl+) = ?0.3±0.9 kcal mol?1 was calculated from the results. The major features on the PIE curve for C2H4 · HCl+ can be analyzed in terms of the known energetic features of C2H 4 + and HCl. An extended energy diagram for the C2H4 + HCl system is presented.  相似文献   

6.
An electron spectrometric study has been performed on HCl using metastable helium and neon atoms as well as neon resonance photons. High resolution electron spectra were obtained with two different beam apparatuses for a mixed He(21 S, 23 S) beam, a pure He(23 S) beam, and, for the first time, state-selected pure Ne(3s 3 P 2) and pure Ne(3s 3 P 0) beams, and for NeI resonance photons. For the system He(23 S)+HCl the vibrational populationsP(υ′) of the formed HCl+ (X 2 i , υ′) and HCl+ (A 2Ω+, υ′) ions are found to differ from the Franck-Condon factors for unperturbed potentials, indicating slight bond stretching in HCl upon He(23 S) approach. For He(21 S)+HCl the vibrational peak shapes and vibrational populations are substantially different from the He(23 S) case, pointing to an additional, charge exchanged interaction (He++HCl?) in the entrance channel of the former system. For the first time, we have detected the electrons in both the He(21 S)+HCl and He(23 S)+HCl spectra associated with the major mechanism for the formation of Cl+ ions: energy transfer to repulsive HCl** Rydberg states, dissociating toH(1s) and autoionizing Cl**(1 D 2 nl) atoms. For both Ne(3 P 2)+HCl and Ne(3 P 0)+HCl, the populationsP(υ′) of both final molecular states HCl+ (X, A) agree closely with the Franck-Condon factors at the average relative collision energyē coll=55 meV and, for HCl+ (A 2Ω+), also atē coll=130 meV.  相似文献   

7.
8.
In comparison to stimuli-responsive, multi-functional nanoparticles (NPs) from synthetic polymers, such NPs based on sustainable, naturally occurring polysaccharides are still scarce. In the present study, stable stimuli-responsive, fluorescent and magnetic NPs were fabricated using cellulose stearoyl esters (CSEs) consisting of cellulose and stearoyl groups. The multifunctional NPs with the average diameters between 80 and 250 nm were obtained after facile nanoprecipitation using CSE solutions containing Fe3O4-NPs. Using the aqueous solution of fluorescent rhodamine B as precipitant, NPs with rhodamine B on NP surface were obtained. Rhodamine B could be released depending on the temperature. In comparison, stearoylaminoethyl rhodamine B can be encapsulated in CSE-NPs, which renders obtained NPs reversible fluorescence in response to UV illumination and heat treatment.  相似文献   

9.
Using a beam apparatus, we have measured the HCl+ (A,v′→X,v″) fluorescence spectra of HCl+ (A,v′) ions formed in HeI (58.4 nm), and NeI (73.6 nm) photoionization and, for the first time, in He (23 S) Penning ionization under single collision conditions with a wavelength bandwidth around 1 nm. In addition, we have studied Ne (3s 3 P 2, 0) Penning ionization of HCl at three different collision energies. The procedure and the problems in extracting HCl+ (A,v′) vibrational populations from the data are discussed in some detail. Thedirect comparison of photoionization and Penning ionization data allows definitive conclusions to be drawn on the question whether final state interactions in the Penning reaction change the “nascent” vibrational population (determined by electron spectrometry); for He (23 S)+HCl, such changes are shown to be absent within the experimental uncertainty (<±10%). For Ne (3s 3 P 2, 0)+HCl, the HCl+ (A,v′=0, 1) populations are also found to be close to those measured by electron spectrometry and essentially independent of collision energy in the range 34–96 meV. From measurements of the fluorescence intensity as a function of HCl density, we have evidence for a fast loss of HCl+ (A,v′) ions in collisions with HCl (rate constant around 5·10?9 cm3s?1).  相似文献   

10.
A complete characterization of the different physico-chemical properties of nanoparticles (NPs) is necessary for the evaluation of their impact on health and environment. Among these properties, the surface characterization of the nanomaterial is the least developed and in many cases limited to the measurement of surface composition and zetapotential. The biological surface adsorption index approach (BSAI) for characterization of surface adsorption properties of NPs has recently been introduced (Xia et al. Nat Nanotechnol 5:671–675, 2010; Xia et al. ACS Nano 5(11):9074–9081, 2011). The BSAI approach offers in principle the possibility to characterize the different interaction forces exerted between a NP's surface and an organic—and by extension biological—entity. The present work further develops the BSAI approach and optimizes a solid-phase microextraction gas chromatography–mass spectrometry (SPME/GC-MS) method which, as an outcome, gives a better-defined quantification of the adsorption properties on NPs. We investigated the various aspects of the SPME/GC-MS method, including kinetics of adsorption of probe compounds on SPME fiber, kinetic of adsorption of probe compounds on NP's surface, and optimization of NP's concentration. The optimized conditions were then tested on 33 probe compounds and on Au NPs (15 nm) and SiO2 NPs (50 nm). The procedure allowed the identification of three compounds adsorbed by silica NPs and nine compounds by Au NPs, with equilibrium times which varied between 30 min and 12 h. Adsorption coefficients of 4.66?±?0.23 and 4.44?±?0.26 were calculated for 1-methylnaphtalene and biphenyl, compared to literature values of 4.89 and 5.18, respectively. The results demonstrated that the detailed optimization of the SPME/GC-MS method under various conditions is a critical factor and a prerequisite to the application of the BSAI approach as a tool to characterize surface adsorption properties of NPs and therefore to draw any further conclusions on their potential impact on health. Graphical Abstract
The basic principle of SPME/GC-MS method for characterization of nanoparticles surface adsorption forces  相似文献   

11.
To understand the relationship between the morphology of carboxyl-functionalized polystyrene/silica (PS/SiO2) nanocomposite microspheres and the surface-enhanced Raman scattering (SERS) performance of PS/SiO2/Ag nanocomposite particles, core-shell and raspberry-like PS/SiO2 composite microspheres were used as templates to prepare PS/SiO2/Ag nanocomposite particles. The core-shell and raspberry-like structured PS/SiO2 templates were prepared via in situ sol-gel reaction by hydrolysis tetraethyl orthosilicate (TEOS) in alkali solution. Silver nanoparticles (10–50 nm) were loaded on the PS/SiO2 templates’ surface by chemical reduction. The morphology and structure of the PS/SiO2/Ag particles were characterized by TEM, SEM, X-ray diffraction (XRD), and ultraviolet-visible (UV-vis) spectroscopy. Rhodamine 6G (R6G) was selected as a model chemical to study the enhancement performance of substrate constructed by PS/SiO2/Ag nanocomposite. Results indicated that the PS/SiO2/Ag nanocomposite prepared based on the core-shell templates showed higher SERS activity. The beneficial effect was associated with a lower specific area of core-shell structure and the larger average diameter of nanosilvers than that of the raspberry-like templates.  相似文献   

12.
A highly porous silica-supported tungstophosphoric acid (PW) nanocluster was prepared for use in solid-phase microextraction (SPME) of polycyclic aromatic hydrocarbons (PAHs). The PWs represent a class of discrete transition metal-oxide nanoclusters and their structures resemble discrete fragments of metal-oxide structures of definite size and shape. Transition metal-oxide nanoclusters display large structural diversity, and their monodisperse sizes can be tuned from several Ångstroms up to 10 nm. The highly porous silica-supported tungstophosphoric acid nanocluster material is found to be capable of efficiently extracting PAHs from aqueous sample solutions. The nanomaterial was immobilized on a stainless steel wire for fabrication of the SPME fiber. Following thermal desorption, the PAHs were quantified by GC-MS. Analytical merits include limits of detection that range from 0.02 to 0.1 pg mL?1 and a dynamic range as wide as from 0.001 to 100 ng mL?1. Under optimum conditions, the repeatability for one fiber (n?=?3), expressed as the relative standard deviation, is between 4.3 % and 8.6 %. The method is simple, rapid, and inexpensive. The thermal stability of the fiber and the high relative recovery make this method superior to conventional methods of extraction.
The highly porous silica-supported tungstophosphoric acid nanocluster material is found to be capable of efficiently extracting PAHs from aqueous sample solutions. The prepared nanomaterial was immobilized onto a stainless steel wire for fabrication of the SPME fiber. Following thermal desorption, the PAHs were quantified by GC-MS.  相似文献   

13.
The ZnO nanoparticles (ZnONPs) were synthesized with gelatin as stabilizer via the sol-gel method and were characterized by transmission electron microscope (TEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). An electrochemical sensor based on ZnO nanoparticles-multi wall carbon nanotubes-poly methyl metacrylat (ZnONPs-MWCNT-PMMA) composite film was developed by incorporating Ni2+ into the ZnONPs-MWCNT-PMMA film modified carbon paste electrode (Ni2+/ZnONPs-MWCNT-PMMA/CPE). The electrochemical activity of Ni2+/ZnONPs-MWCNT-PMMA/CPE was illustrated in 0.10 M NaOH using cyclic voltammetry. The Ni2+/ZnONPs-MWCNT-PMMA/CPE exhibits the characteristic of improved reversibility and enhanced current responses of the Ni(III)/Ni(II) couple. Ni2+/ZnONPs-MWCNT-PMMA/CPE also show good electrocatalytic activity toward the oxidation of carbohydrates (glucose, fructose and sorbitol). The Ni2+/ZnONPs-MWCNT-PMMA/CPE gives a good linear range with a detection limit of 8, 6, and 9 μM towards the determination of glucose, fructose and sorbitol, respectively by amperometry. Furthermore, the modified sensor was successfully applied to the sensitive determination of carbohydrates in real samples.  相似文献   

14.
The heat of reaction and kinetics of curing of diglycidyl ether of bisphenol-A (DGEBA) type of epoxy resin with catalytic amounts of ethylmethylimidazole (EMI) have been studied by differential power-compensated calorimetry as a part of the program for the study of process monitoring for composite materials. The results were compared with those from 1∶1 and 1∶2 molar mixtures of DGEBA and EMI. A method of determination of heat of reaction from dynamic thermoanalytical instruments was given according to basic thermodynamic principles. The complicated mechanism, possibly involving initial ionic formation, has also been observed in other measurements, such as by time-domain dielectric spectroscopy. The behavior of commercially available DGEBA resin versus purified monomeric DGEBA were compared. The melting point of purified monomeric DGEBA crystals is 41.4 °C with a heat of fusion of 81 J/g. The melt of DGEBA is difficult to crystallize upon cooling. The glass transition of purified DGEBA monomer occurs around ?22 °C with aΔC p of 0.60 J/K/g.  相似文献   

15.
High-density polyethylene (HDPE) containing various volume fractions (0–20 vol%) of aluminum nitride nanoparticles (n-AlN) is prepared by melt mixing. Structural and morphological characterizations of the prepared composites are carried out by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), and atomic force microscopy (AFM). Thermal stability and degradation kinetics of HDPE/AlN (nano) composites are investigated by Thermogravimetric analysis (TG). HR-TEM micrographs confirm fairly uniform dispersion of AlN nanoparticles, as well as the existence of long interconnected chain-like aggregates. AFM images also confirm homogeneous dispersion of n-AlN in the polymer matrix. Roughness analysis from the AFM data indicates the presence of substantial undulation from the mean surface level. Thermogravimetric data indicate small improvement in the thermal stability of the composites. Kinetic parameters, viz., the activation energy (E a), frequency factor (A), and reaction order (n) are estimated using the isoconversional methods of Kissinger, Flynn–Wall–Ozawa (FWO), KAS, and Friedman. Activation energies (E a) calculated by the above four models display nearly similar features and are enhanced by the presence of AlN nanoparticles. Kinetics of degradation of HDPE-AlN (nano) composites follows a first-order reaction.  相似文献   

16.
Decomposition yields of tetracycline hydrochloride /TC.HCl/ and chlorotetracycline hydrochloride /ClTC?HCl/ in methanol solution saturated with Ar or N2O were determined. Rate constants of the reaction es with some antibiotics were obtained: $$\begin{gathered} k/e_s^ - + ClTC \cdot HCl/ = 2 \cdot 49 \times 10^8 dm^3 \cdot mole^{ - 1} \cdot s^{ - 1} ; \hfill \\ k/e_s^ - + TC \cdot HCl/ = 2 \cdot 86 \times 10^8 dm^3 \cdot mole^{ - 1} \cdot s^{ - 1} \cdot \hfill \\ \end{gathered} $$ On the basis of the diffence between decomposition yields: ΔG=G?TC.HCl?G?ClTC.HCl′ 7-C?Cl group decomposition yield and the rate constant $$k/e_s^ - + Cl - C - 7/ = 7 \cdot 94 \times 10^8 dm^3 \cdot mole^{ - 1} \cdot s^{ - 1} $$ were determined. It was demonstrated by1H NMR that the radical formed by degradation of 7-C?Cl group is recombined with the H atoms leading to ClTC.HCl being converted into tetracycline hydrochloride /TC.HCl/.  相似文献   

17.
More than 13 years of SIMS application field experience of numerous users of the ATOMIKA Ionmicroprobes have been the basis for the new SIMS Data System SDS 800. The hardware and software concept of the SDS 800, therefore, pays special attention to the following requirements:
  1. Convenient set-up, modification and re-use of the measuring parameter sets for easy, time-saving operation.
  2. Individual parameter selection from the very broad range of SIMS measuring parameters for optimum SIMS data quality.
  3. Multitasking operation for simultaneous handling of SIMS measurement, data processing, data output and of auxiliary techniques.
  4. Simultaneous depth profile/ion image acquisition and processing to enhance data quality and to validate data interpretation.
  5. User-friendly data processing and output.
  相似文献   

18.
TG and DTA data are used to show that the thermal decomposition of polymethylmethacrylate (PMMA) synthesized with anionic catalysts depends on the nature of the catalyst. It is found that the thermal stability of PMMA obtained by using anionic amide catalysts is higher than that of radical PMMA and of PMMA obtained with other anionic catalysts, and depends on the temperature of polymerization and on the molecular weight of the polymer.  相似文献   

19.
The kinetics of HCl oxidation at 350–425°C over the supported CuCl2-KCl-LaCl3 catalyst has been investigated using a gradientless technique. The HCl oxidation kinetics in the Deacon and methane oxychlorination reactions has been studied in order to substantially extend the \(Cl_2 \left( {P_{Cl_2 } } \right)\) partial pressure variation range. When the reaction rate is independent of P HCl, HCl oxidation on the copper-potassium catalysts is described by the same rate equation, irrespective of whether the catalyst contains lanthanum or not. The introduction of lanthanum chloride increases the HCl oxidation rate by one order of magnitude. The rate equation obtained has significant advantages over the equation corresponding to the Kenney-Slama equation. The kinetic features of HCl oxidation over the lanthanum-containing catalyst, whether the process depends on P HCl or not, can be explained in terms of the superposition of the Kenney-Slama dissociative mechanism and the catalytic mechanism suggested here. The role of lanthanum chloride in both HCl oxidation pathways is considered.  相似文献   

20.
The role of two cations [tetraethylammonium+ (TEA+) and tetrabutylammonium+ (TBA+)] in the homogeneous succinoylation of mulberry wood (MW) cellulose in dimethyl sulfoxide (DMSO)/tetraethylammonium chloride (TEACl) and DMSO/tetrabutylammonium fluoride (TBAF) was investigated using the intrinsic viscosity and two-dimensional nuclear Overhauser effect NMR spectroscopy (2D NOESY). The intrinsic viscosity of MW cellulose solution strongly depends on the salt dosage for both TEACl and TBAF, indicating that the increase in the hydrodynamic size of cellulose chains was caused by the interactions between salts and cellulose, which promotes the solvation process of cellulose in solution. Two-dimensional NOESY spectra reveal that cations bind to cellobiose in DMSO by the interactions between α-methylene groups of TEA+ (or TBA+) and C1/C1′ groups of cellobiose, and the intensities of the respective crosspeaks increase with increasing TEACl dosage from 5 to 10 mg/ml, but no change was present with TBAF at the same concentration range. Taking cellobiose as a model compound for cellulose, it can be expected that TEA+ (or TBA+) and cellulose form polyelectrolyte-like complexes. The degree of substitution (DS) of homogeneous succinoylation of MW cellulose benefits from the interactions between TEA+ (or TBA+) and cellulose evidenced by FT-IR spectra and CP/MAS 13C NMR spectra. The DS of the succinylated cellulose declines at TBAF concentrations higher than 11 wt% probably because of the steric hindrance effects of TBA+.  相似文献   

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