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1.
Two enzyme reactors prepared by the co-immobilization of two different glucose-6-phosphate dehydrogenases (G6PDH; from Leuconstoc mescenteroides (LM) and yeast (Y) and diaphorase are employed to enhance the sensitivity of NAD(P) coenzymes as on-line amplifiers based on substrate recycling in a chemiluminometric flow-injection system. The NAD(P) coenzymes are recycled enzymatically during passage through the reactor in the presence of sufficient glucose-6-phosphate and oxygen in the carrier solution to produce a large amount of hydrogen peroxide, which is detected chemiluminometrically in the subsequent flow line. The G6PDH(LM)/diaphorase co-immobilized reactor is not specific between the NAD and NADP coenzymes, but shows a six fold selectivity towards NADP coenzymes compared to NAD coenzymes; the amplification factors for NAD and NADP coenzymes are 60 and 380, respectively, at a flow rate of 0.3 ml min(-1). In contrast, the G6PDH(Y)/diaphorase co-immobilized reactor is specific for NADP coenzymes with an amplification factor of about 600 (at a flow rate of 0.3 ml min(-1)). The detection limit is 6 fmol for both NADP(+) and NADPH. 相似文献
2.
The redox and adsorption behaviour of some redox coenzymes involved in an electron-transport chain, i.e. ubiquinone-10 (CoQ), flavocoenzymes [flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD)] and nicotinamide adenine dinucleotide (NAD+), has been studied at a gold electrode by cyclic voltammetry and specular reflectivity measurement. All the coenzymes investigated were found to participate in electron transport in adsorbed states on the electrode surface. Adsorbed CoQ and flavocoenzymes are reduced and the resulting products remain adsorbed at the surface. Contrary to them, adsorbed NAD+ is reduced and then desorbed immediately. Possible models for the surface orientation of adsorbed molecules were proposed based on the experimental data.Some analogies can be noted between the interfacial behaviour of these coenzymes at the electrode and that in mitochondria. 相似文献
3.
《Bioelectrochemistry and bioenergetics (Lausanne, Switzerland)》1982,9(4):499-508
The redox and adsorption behaviour of some redox coenzymes involved in an electron-transport chain, i.e. ubiquinone-10 (CoQ), flavocoenzymes [flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD)] and nicotinamide adenine dinucleotide (NAD+), has been studied at a gold electrode by cyclic voltammetry and specular reflectivity measurement. All the coenzymes investigated were found to participate in electron transport in adsorbed states on the electrode surface. Adsorbed CoQ and flavocoenzymes are reduced and the resulting products remain adsorbed at the surface. Contrary to them, adsorbed NAD+ is reduced and then desorbed immediately. Possible models for the surface orientation of adsorbed molecules were proposed based on the experimental data.Some analogies can be noted between the interfacial behaviour of these coenzymes at the electrode and that in mitochondria. 相似文献
4.
《中国化学快报》2019,30(9):1659-1662
The development of efficient methods for the detection of hazardous and toxic elements is extremely important for environmental security and public health. In this work, we developed a facile colorimetric assaying system for Ag+ detection in aqueous solution. Chitosan-stabilized platinum nanoparticles (Ch-PtNPs) were synthesized and severed as an artificial oxidase to catalyze the oxidation of the substrate 3,3′,5,5′-tetramethylbenzidine (TMB) and generate color signal. In the presence of Ag+, due to the strong metallophilic interactions between Ag+ and Pt2+ on the surface of Ch-PtNPs, Ag+ can weaken the affinity to the substrates and inactivate the catalytic activity of Ch-PtNPs, leading to decreased absorbance signal to varying degrees depending on Ag+ amount. Combing the specific binding between Ch-PtNPs and Ag+ with signal amplification procedure based on the Ch-PtNPs-catalyzed TMB oxidation, a sensitive, selective, simple, cost-effective, and rapid detection method for Ag+ can be realized. Ag+ ions in tap and lake waters have been successfully detected. We ensured that the proposed method can be a potential alternative for Ag+ determination in environmental samples. 相似文献
5.
The heavy metal ions-nucleobases interaction is an important research topic in environmental and biochemical analysis. The presence of the silver ion (Ag+) may influence the formation of oxidation intermediate and the electrocatalytic oxidation activity of guanine (G), since Ag+ can interact with guanine at the binding sites which are involved in the electrocatalytic oxidation reaction of guanine. According to this principle, a new electrochemical sensor for indirectly detecting Ag+ based on the interaction of Ag+ with isolated guanine base using differential pulse voltammetry (DPV) was constructed. Among the heavy metal ions examined, only Ag+ showed the strongest inhibitory effect on the electrocatalytic oxidation of guanine at the multi-walled carbon nanotubes modified glassy carbon electrode (CNTs/GC). And the quantitative study of Ag+ based on Ag+-G sensing system gave a linear range from 100 nM to 2.5 μM with a detection limit of 30 nM. In addition, this modified electrode had very good reproducibility and stability. The developed electrochemical method is an ideal tool for Ag+ detection with some merits including remarkable simplicity, low-cost, and no requirement for probe preparation. 相似文献
6.
A new dual detection system for microchip is reported. Both fluorescence detector (FD) and contactless conductivity detector (CCD) were combined together and integrated on a microfluidic chip. They shared a common detection position and responded simultaneously. A blue light-emitting diode was used as excitation source and a small planar photodiode was used to collect the emitted fluorescence in fluorescence detection, which made the device more compact and portable. The coupling of the fluorescence and contactless conductivity modes at the same position of a single separation channel enhanced the detection characterization of sample and offered simultaneous detection information of both fluorescent and charged specimen. The detection conditions of the system were optimized. K+, Na+, fluorescein sodium, fluorescein isothiocyanate (FITC) and FITC-labeled amino acids were used to evaluate the performance of the dual detection system. The limits of detection (LOD) of FD for fluorescein Na+, FITC, FITC-labeled arginine (Arg), glycine (Gly) and phenylalanine (Phe) were 0.02 μmol L−1, 0.05 μmol L−1, 0.16 μmol L−1, 0.15 μmol L−1, 0.12 μmol L−1 respectively, and the limits of detection (LOD) of CCD achieved 0.58 μmol L−1 and 0.39 μmol L−1 for K+ and Na+ respectively. 相似文献
7.
Hongxia Sun Hongbo Chen Xiufeng Zhang Yan Liu Aijiao Guan Qian Li Qianfan Yang Yunhua Shi Shujuan Xu Yalin Tang 《Analytica chimica acta》2016
There has been a big challenge in developing the Na+ sensor that can be practically used in the physiological system with the interference of large amounts of K+. In this research, a novel Na+ sensor has been designed based on the G-quadruplex-conformation related DNAzyme activity. The sensor exhibits high selectivity and sensitivity with the detection limit of 0.6 μM, which enables the sensor to be practically used in determination of the Na+ level in serum. The research not only provides a simple Na+ sensor but also opens a new way for developing the detection technology of Na+. 相似文献
8.
《Arabian Journal of Chemistry》2023,16(2):104492
In this study, a portable silver ion (Ag+) sensor was fabricated based on a dual signal output system using black phosphorus quantum dots (BPQDs) as probes. It is the first work for Ag+ detection using paper test strip based on BPQDs. The color change of BPQDs paper sensor for the determination of Ag+ was easily identified by naked eye. BPQDs were synthesized from bulk black phosphorus (BP) by mechanical exfoliation combined with a solvothermal method. BPQDs exhibited blue fluorescence with a quantum yield of 8.82 %. The fluorescence of BPQDs can be quenched by Ag+, and the absorbance of BPQDs is increased with increasing Ag+ concentration. The mechanism of the interaction between BPQDs and Ag+ involving fluorescence quenching and bonding was investigated by experimental and computational methods. The detection limit of Ag+ was 1.56 μg/mL and 0.19 μg/mL using fluorometry and colorimetry methods, respectively. A portable visual sensor based on paper test strip was constructed for Ag+ detection using the colorimetric approach. The strategy was employed to determine Ag+ successfully in drinking water samples. Therefore, the proposed portable Ag+ sensor can be potentially utilized for the lab-free analysis of drinking water and even dietary samples. 相似文献
9.
Bio-amperometric flow-injection systems are proposed for the highly selective and sensitive determination of phosphate. One system studied is based on the use of a co-immobilized purine nucleoside phosphorylase-xanthine oxidase reactor, which responds to phosphate with high selectivity, and a detection limit of 3 × 10?7 M for a 20-μl injection. Another system with a co-immobilized purine nucleoside phosphorylase-xanthine oxidase-alkaline phosphatase reactor gives responses amplified by substrate recycling during passage through the enzyme reactor. Phosphate can be determined with 12 times the sensitivity in the latter system compared with the former, but the latter system responds to nucleotides and pyrophosphate in addition to orthophosphate. 相似文献
10.
Zhijuan Cao Pei Wang Xue Qiu Choiwan Lau Jianzhong Lu 《Analytical and bioanalytical chemistry》2014,406(7):1895-1902
Herein, we demonstrate a novel silver nanocluster-based fluorescent system for the detection of nicotinamide adenine dinucleotide (NAD+), an important biological small molecule involved in a wide range of biological processes. A single-stranded dumbbell DNA probe was designed and used for the assay, which contained a nick in the stem, a poly-cytosine nucleotide loop close to 5′ end as the template for the formation of highly fluorescent silver nanoclusters (Ag NCs) and another loop close to 3′ end. Only in the presence of NAD+, the probe was linked at 5′ and 3′ ends by Escherichia coli DNA ligase, which blocked the DNA polymerase-based extension reaction, ensuring the formation of fluorescent Ag NCs. This technique provided a logarithmic linear relationship in the range of 1 pM–500 nM with a detection limit of as low as 1 pM NAD+, and exhibited high selectivity against its analogues, and was then successfully used for the detection of NAD+ level in four kinds of cell homogenates. In addition, this new approach was conducted in an isothermal and homogeneous condition without the need of any thermal cycling, washing, and separation steps, making it very simple. Overall, this label-free protocol offers a promising alternative for the detection of NAD+, taking advantage of specificity, sensitivity, cost-efficiency, and simplicity. Figure
Ligation triggered fluorescent silver nanoclusters system for nicotinamide adenine dinucleotide sensing 相似文献
11.
We report on a novel method for the determination of silver ion (Ag+) and cysteine (Cys) by using the probe SYBR Green I (SGI) and an Ag+-specific cytosine-rich oligonucleotide (C-DNA). The fluorescence of SGI is very weak in the absence or presence of randomly coiled C-DNA. If, however, C-DNA interacts with Ag+ through the formation of cytosine-Ag+-cytosine (C-Ag+-C) base pairs, the randomly coiled C-DNA undergoes a structural changes to form a hairpin-like structure, thereby increasing the fluorescence of SGI. This fluorescence turn-on process allows the detection of Ag+ in the 10–600?nM concentration range, with a detection limit of 4.3?nM. Upon the reaction of Ag+ with Cys, Cys specifically removes Ag+ from the C-Ag+-C base pairs and destroys the hairpin-like structure. This, in turn, results in a decrease in fluorescence intensity. This fluorescence turn-off process enables the determination of Cys in the 8–550?nM concentration range, with a detection limit of 4.5?nM. The method reported here for the determination of either Ag+ or Cys is simple, sensitive, and affordable, and may be applied to other detection systems if appropriately selected DNA sequences are available. Figure
Sencitive and selective detection of Ag+ and cysteine based on fluorescence change of SYBR Green I 相似文献
12.
A unique photoluminescence carbon dots (CDs) with larger size were prepared by microwave-assisted method. Complex functional groups on the surface of the CDs facilitate the nanoparticles to form affinity with some metal ions. Taking advantage of the effective fluorescence quenching effect of K+, a highly sensitive CD-based fluorescence analytical system for label-free detection of K+ with limit of detection (LOD) 1.0 × 10−12 M was established. The concentrations of potassium ion in biological samples such as human serum are usually found at millimolar levels or even higher. The proposed method begins with a substantial dilution of the sample to place the K+ concentration in the dynamic range for quantification, which covers 3 orders of magnitude. This offers some advantages: the detection of K+ only needs very small quantities of biological samples, and the dilution of samples such as serum may effectively eliminate the potential interferences that often originate from the background matrix. The determined potassium levels were satisfactory and closely comparable with the results given by the hospital, indicating that this fluorescent probe is applicable to detection of physiological potassium level with high accuracy. Compared with other relative biosensors requiring modified design, bio-molecular modification or/and sophisticated instruments, this CD-based sensor is very simple, cost-effective and easy detection, suggesting great potential applications for successively monitoring physiological potassium level and the change in biological system. 相似文献
13.
A G-quadruplex-hemin DNAzyme-amplified Ag+-sensing method was developed based on the ability of Ag+ to stabilize C-C mismatches by forming C-Ag+-C base pairs. In this method, only one unlabelled oligonucleotide strand was used. In the absence of Ag+, the oligonucleotide strand formed an intramolecular duplex. The G-rich sequence in the oligonucleotide was partially caged in this duplex structure and cannot fold into the G-quadruplex structure. The addition of Ag+ promoted the formation of another intramolecular duplex in which C-C mismatches were stabilized by C-Ag+-C base pairs, leading to the release of the G-rich sequence which can fold into a G-quadruplex capable to bind hemin to form a catalytically active G-quadruplex-hemin DNAzyme. As a result, a UV-vis absorbance increasing was observed in the H2O2-ABTS (2,2′-azinobis(3-ethylbenzothiozoline)-6-sulfonic acid) reaction system. This “turn-on” process allowed the detection of aqueous Ag+ at concentrations as low as 6.3 nM using a simple colorimetric technique, showing a high selectivity over a range of other metal ions. 相似文献
14.
Yunhua Shi Hongxia Sun Junfeng Xiang Lijia Yu Qianfan Yang Qian Li Aijiao Guan Yalin Tang 《Analytica chimica acta》2015
A novel Ag+ sensor has been designed based on the mechanism that i-motif formation induced by Ag+ was sensitively recognized by a cyanine dye. The sensor exhibited an over 130–16,000 fold selectivity toward Ag+ than that toward other metal ions. This research not only provides a step forward toward the development of Ag+ detection but also represents a new application for i-motif DNA. 相似文献
15.
A liquid chromatographic ultraviolet absorption detector (at 195 nm) and a novel postcolumn reactor detector are compared for use in the detection of triglyceride and phospholipid molecular species. The detection limit for the u.v. detector depends on the degree of unsaturation of the lipid sample (3 × 10-6–2 × 10-8 M in the detector cell for 0–3 double bonds per acyl group). The post-column reactor detector is responsive to equivalents of lipid and has detection limits of 5 × 10-7 M for triglycerides and 2 × 10-6 M for phospholipids. The log u.v./post-column reactor detector response ratios are linearly related to the log of the degree of unsaturation of the lipid, indicating the usefulness of both detectors for quantifying triglycerides and phospholipids. 相似文献
16.
An ion-exclusion chromatographic method for the direct UV detection of non-absorbing inorganic cations such as sodium (Na+), ammonium (NH4+) and hydrazine (N2H5+) ions was developed by connecting an anion-exchange column in the I−-form after the separation column. For example, NH4+ is converted to a UV-absorbing molecule, NH4I, by the anion-exchange column in the I−-form after the ion-exclusion separation on anion-exchange column in the OH−-form with water eluent. As a result, the direct UV detection of Na+, NH4+ and N2H5+ could be successfully obtained as well as the well-resolved separation. The calibration graphs of the analyte cations detected with UV at 230 nm were linear in the range of 0.001-5.0 mM. The detection limits at S/N = 3 of the cations were below 0.1 μM. This method was applied to real water analysis, the determination of NH4+ in river and rain waters, or that of N2H5+ in boiler water, with the satisfactory results. This could be applied also to low- or non-absorbing anions such as fluoride or hydrogencarbonate ions by the combination of a weakly acidic cation-exchange resin in the H+-form as the separation column and the anion-exchange conversion column. 相似文献
17.
《Analytical letters》2012,45(5-6):649-665
Abstract A miniaturized flow injection system for the determination of D-glucose, L-lactic acid, creatinine and free cholesterol is described. All substrates are degraded enzymatically by means of oxidases which, along with ancillary coenzymes (creatinine assay), are immobilized on controlled porosity glass and incorporated into small PVC column reactors. The hydrogen peroxide generated by the individual oxidases is determined by chemiluminescence with an alkaline reagent containing luminol and hexacyanofer rate (III). The injection valve, flow channels, enzyme reactor and light detector are integrated into a FIA microconduit. The detection limits were 0.03 mg glucose/dl, 0.03 mg lactate/dl, 0.3 mM creatinine and 0.5 mg cholesterol/dl. The enzyme reactors all showed little change in activity over a 3 months period of operation and were found fully compatible with serum samples. 相似文献
18.
Mori M Kaseda M Yamamoto T Yamada S Itabashi H 《Analytical and bioanalytical chemistry》2012,402(7):2425-2430
Capillary ion electrophoresis–capacitively coupled contactless conductivity detection (CIE-C4D) with a polyvinyl alcohol chemically
coated capillary (PVA capillary) was used to analyze inorganic cations (Na+, K+, NH4+, Mg2+, and Ca2+) commonly found in human saliva. The PVA capillary, which was made by our laboratory, minimized electro-osmotic flow in the
wide pH range of the background electrolyte (BGE), and the PVA layer adsorbed to capillary wall did not affect the conductimetric
background level. In this study, we determined an optimized BGE of 30 mM lactic acid/histidine plus 3 mM 18-crown-6 for the
CIE-C4D system using the PVA capillary, which could simultaneously improve the separation of Mg2+ and Ca2+ from Na+ and that of K+ from NH4+. This system obtained highly reproducible separation of cations in human saliva samples within 8 min at 20 kV without deprotonation.
The quantifiability of cations in human saliva samples on the CIE-C4D system was demonstrated through identification by ion
chromatography with satisfactory results. 相似文献
19.
Ion chromatography with the indirect ultraviolet detection of alkali metal ions and ammonium using imidazolium ionic liquid as ultraviolet absorption reagent and eluent
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Indirect ultraviolet detection was conducted in ultraviolet‐absorption‐agent‐added mobile phase to complete the detection of the absence of ultraviolet absorption functional group in analytes. Compared with precolumn derivatization or postcolumn derivatization, this method can be widely used, has the advantages of simple operation and good linear relationship. Chromatographic separation of Li+, Na+, K+, and NH4+ was performed on a carboxylic acid base cation exchange column using imidazolium ionic liquid/acid/organic solvent as the mobile phase, in which imidazolium ionic liquids acted as ultraviolet absorption reagent and eluting agent. The retention behaviors of four kinds of cations are discussed, and the mechanism of separation and detection are described. The main factors influencing the separation and detection were the background ultraviolet absorption reagent and the concentration of hydrogen ion in the ion chromatography‐indirect ultraviolet detection. The successful separation and detection of Li+, Na+, K+, and NH4+ within 13 min was achieved using the selected chromatographic conditions, and the detection limits (S/N = 3) were 0.02, 0.11, 0.30, and 0.06 mg/L, respectively. A new separation and analysis method of alkali metal ions and ammonium by ion chromatography with indirect ultraviolet detection method was developed, and the application range of ionic liquid was expanded. 相似文献
20.
1. Cacotheline has previously been employed as a colorimetric reagent for the detection of Sn+2 and V+3 ions. The present investigation covers its use as a reagent for the detection of Fe+2 and Fe+3 ions. 2. Fe+2 ions give a pink colour with a solution of cacotheline at a pH lying between 1.48 and 4.58 in the presence of a sufficient concentration of sodium oxalate, which serves to bind the Fe+3 ions by complex formation. At a pH below 1.24, only a very light pink colour is produced and this develops slowly. When the pH of the solution is about 5.2, a blue colour is obtained. The limit of identification is 1.5 γ and the concentration limit is 1 : 40,000 of Fe+2. While testing for Fe+2 at very low concentration, it is necessary to employ a very dilute solution of cacotheline (0.025%), while for solutions of higher concentrations saturated cacotheline solution (about 0.25%) is recommended. A detailed investigation has been made concerning the conditions determining the stability of the pink colour. 3. It has also been observed that sodium malonate, sodium citrate, sodium malate, sodium tartrate and sodium lactate are effective as complexing agents for binding Fe+3 ions. 4. Orthophosphate has not been found effective as a complexing agent under the conditions adopted, while pyrophosphate and metaphosphate have been found effective. 5. Fe+3 ions are reduced to Fe+2 by exposure to sunlight or the light from a Philip's Repro lamp in the presence of the appropriate buffer solution and sodium oxalate. 相似文献