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(1) Background: Particulate methane monooxygenase (pMMO) has a strong dependence on the natural electron transfer path and is prone to denaturation, which results in its redox activity centers being unable to transfer electrons with bare electrodes directly and making it challenging to observe an electrochemical response; (2) Methods: Using methanobactin (Mb) as the electron transporter between gold electrodes and pMMO, a bionic interface with high biocompatibility and stability was created. The Mb-AuNPs-modified functionalized gold net electrode as a working electrode, the kinetic behaviors of pMMO bioelectrocatalysis, and the effect of Mb on pMMO were analyzed. The CV tests were performed at different scanning rates to obtain electrochemical kinetics parameters. (3) Results: The values of the electron transfer coefficient (α) and electron transfer rate constant (ks) are relatively large in test environments containing only CH4 or O2. In contrast, in the test environment containing both CH4 and O2, the bioelectrocatalysis of pMMO is a two-electron transfer process with a relatively small α and ks; (4) Conclusions: It was inferred that Mb formed the complex with pMMO. More importantly, Mb not only played a role in electron transfer but also in stabilizing the enzyme structure of pMMO and maintaining a specific redox state. Furthermore, the continuous catalytic oxidation of natural substrate methane was realized.
Assuntos
Ouro , Imidazóis , Nanopartículas Metálicas , Oligopeptídeos , Oxigenases , Ouro/química , Cobre/química , Nanopartículas Metálicas/química , Oxirredução , Minerais , Metano/química , EletrodosRESUMO
Particulate methane monooxygenase (pMMO) is a characteristic membrane-bound metalloenzyme of methane-oxidizing bacteria that can catalyze the bioconversion of methane to methanol. However, in order to achieve pMMO-based continuous methane-to-methanol bioconversion, the problems of reducing power in vitro regeneration and pMMO stability need to be overcome. Methanobactin (Mb) is a small copper-chelating molecule that functions not only as electron carrier for pMMO catalysis and pMMO protector against oxygen radicals, but also as an agent for copper acquisition and uptake. In order to improve the activity and stability of pMMO, methanobactin-Cu (Mb-Cu)-modified gold nanoparticle (AuNP)-pMMO nanobiohybrids were straightforwardly synthesized via in situ reduction of HAuCl4 to AuNPs in a membrane fraction before further association with Mb-Cu. Mb-Cu modification can greatly improve the activity and stability of pMMO in the AuNP-pMMO nanobiohybrids. It is shown that the Mb-Cu-modified AuNP-pMMO nanobiohybrids can persistently catalyze the conversion of methane to methanol with hydroquinone as electron donor. The artificial heterogeneous nanobiohybrids exhibited excellent reusability and reproducibility in three cycles of catalysis, and they provide a model for achieving hydroquinone-driven conversion of methane to methanol.
Assuntos
Proteínas de Bactérias/química , Enzimas Imobilizadas/química , Ouro/química , Imidazóis/química , Nanopartículas Metálicas/química , Methylosinus trichosporium/enzimologia , Oligopeptídeos/química , Oxigenases/química , Estabilidade EnzimáticaRESUMO
Chemical composition and rumen degradability of waste vinegar residue (WVR) as roughage feed used for mutton sheep were evaluated in this work. Compared with the unfermented WVR, the WVR fermented by N. sitophila had more (P < 0.01) ash, crude protein (CP), and true protein (TP), less (P < 0.01) ether extract (EE), and significantly more carotenoid by about 27 times. But the contents of dry matter (DM), crude fiber (CF), neutral detergent fiber (NDF), and acid detergent fiber (ADF) had no obvious differences (P > 0.05) between unfermented and fermented WVR. The results suggested that the nutritional value of fermented WVR was higher for mutton sheep as roughage feed than that of unfermented WVR. The effective degradability (ED) of DM was higher (P < 0.05) in sheep with fermented WVR-based diet. The ED of CP and NDF of fermented WVR was reduced (P < 0.01) compared with the unfermented WVR. The results further suggested that the fermentation improved the degradability of WVR, and the rumen degradability of protein by ruminal flora decreased in fermented WVR, saving more protein for the sheep post-ruminal digestion and absorption. Furthermore, the results presented here clearly indicated the potential of fermented WVR by N. sitophila as an unconventional and functional feedstuff with rich carotenoid for ruminants, which could reduce WVR discharge in vinegar brewing industry and improve ruminant production. This work laid a foundation for the development of ruminant carotenoid functional feed.
Assuntos
Ração Animal/análise , Dieta/veterinária , Fungos/metabolismo , Valor Nutritivo , Rúmen/metabolismo , Ovinos/fisiologia , Ácido Acético , Animais , Fibras na Dieta/metabolismo , Digestão , Fermentação , Masculino , RuminantesRESUMO
Mathanobatins (Mb, Mbtins) were immobilized successfully on nanometer-sized gold colloid particles associated with ß-mercaptoethylamine. The structures of Mb functionalized gold nanoparticles were characterized and confirmed by UV-vis spectroscopy (UV-vis), FTIR spectra and electrochemical analyses. Direct electron transfer between Mb or copper-loading Mbtins and the modified electrode was investigated without the aid of any electron mediator. The copper-loading Mbtins act as a better electrocatalyst for the reduction of H2O2 than Mb. The copper-loading Mb, with which gold nanoparticles were functionalized, as a model enzyme, was immobilized on gold electrode to construct a novel H2O2 biosensor. In pH 6.4 phosphate buffer solution, the reduction and oxidation peak potentials of Mb functionalized gold nanoparticles modified Au electrode (copper-loading Mbtins) were 0.115 and 0.222 V. On the surface, capacitance per unite area (Cd) of Mb functionalized gold nanoparticles modified electrode were 38 µF cm-2. The immobilized Mb displayed the features of a peroxidase and gave an excellent electrocatalytic response to the reduction of H2O2. The detection limit of Mb functionalized gold nanoparticles (copper-loading) were 09 × 10-5 mA/M (S/N = 3). The Michaelis-Menten constant (Km) was 0.787 mM. Good stability and sensitivity were assessed for the biosensor.
RESUMO
Methanobactin (Mb) is a copper-binding peptide that appears to function as an agent for copper sequestration and uptake in methanotrophs. Mb can also bind and reduce Au(III) to Au(0). In this paper, Au/Al2O3 catalysts prepared by a novel incipient wetness-Mb-mediated bioreduction method were used for glucose oxidation. The catalysts were characterized, and the analysis revealed that very small gold nanoparticles with a particle size <4 nm were prepared by the incipient wetness-Mb-mediated bioreduction method, even at 1.0% Au loading (w/w). The influence of Au loading, calcination temperature and calcination time on the specific activity of Au/Al2O3 catalysts was systematically investigated. Experimental results showed that decomposing the Mb molecules properly by calcinations can enhance the specific activity of Au/Al2O3 catalysts, though they acted as reductant and protective agents during the catalyst preparation. Au/Al2O3 catalysts synthesized by the method exhibited optimum specific activity under operational synthesis conditions of Au loading of 1.0 wt % and calcined at 450 °C for 2 h. The catalysts were reused eight times, without a significant decrease in specific activity. To our knowledge, this is the first attempt at the preparation of Au/Al2O3 catalysts by Mb-mediated in situ synthesis of gold nanoparticles.
Assuntos
Óxido de Alumínio/química , Glucose/química , Ouro/química , Imidazóis/química , Nanopartículas Metálicas/química , Oligopeptídeos/química , Catálise , Cristalização , Nanopartículas Metálicas/ultraestrutura , Oxirredução , Espectroscopia Fotoeletrônica , Reciclagem , Espectroscopia de Infravermelho com Transformada de Fourier , Termogravimetria , Difração de Raios XRESUMO
Starch, lipids, and proteins are essential biological macromolecules that play a crucial role in providing energy and nutrition to our bodies. Interactions between these macromolecules have been shown to impact starch digestibility. Understanding and controlling starch digestibility is a key area of research. Investigating the mechanisms behind the interactions of these three components and their influence on starch digestibility is of significant practical importance. Moreover, these interactions can result in the formation of resistant starch, which can be fermented by gut microbiota in the colon, leading to various health benefits. While current research has predominantly focused on the digestive properties of starch in the small intestine, there is a notable gap in understanding the colonic microbial fermentation phase of resistant starch. The benefits of fermentation of resistant starch in the colon may outweigh its glucose-lowering effect in the small intestine. Thus, it is crucial to study the fermentation behavior of resistant starch in the colon. This paper investigates the impact of interactions among starch, lipids, and proteins on starch digestion, with a specific focus on the fermentation phase of indigestible carbohydrates in the colon. Furthermore, valuable insights are offered for guiding future research endeavors.
Assuntos
Microbiota , Amido , Amido Resistente , Fermentação , Lipídeos , ColoRESUMO
Preparation of gold nanoparticles with a narrow size distribution has enormous importance in nanotechnology. Methanobactin (Mb) is a copper-binding small peptide that appears to function as an agent for copper sequestration and uptake in methanotrophs. Mb can also bind and catalytically reduce Au (III) to Au (0). In this study, we demonstrate a facile Mb-mediated one-step synthetic route to prepare monodispersed gold nanoparticles. Continuous reduction of Au (III) by Mb can be achieved by using hydroquinone as the reducing agent. The gold nanoparticles have been characterized by UV-visible spectroscopy. The formation and the surface plasmon resonance properties of the gold nanoparticles are highly dependent on the ratio of Au (III) to Mb in solution. X-ray photoelectron spectroscopy (XPS), fluorescence spectra and Fourier transform-infrared spectroscopy (FT-IR) spectra suggest that Mb molecules catalytically reduce Au (III) to Au (0) with the concomitant production of gold nanoparticles, and then, Mb statically adsorbed onto the surface of gold nanoparticles to form an Mb-gold nanoparticles assembly. This avoids secondary nucleation. The formed gold nanoparticles have been demonstrated to be monodispersed and uniform by transmission electron microscopy (TEM) images. Analysis of these particles shows an average size of 14.9 nm with a standard deviation of 1.1 nm. The gold nanoparticles are extremely stable and can resist aggregation, even after several months.
Assuntos
Ouro/química , Imidazóis/química , Nanopartículas Metálicas/química , Oligopeptídeos/química , Catálise , Microscopia Eletrônica de Transmissão , Espectroscopia de Infravermelho com Transformada de FourierRESUMO
In this study, starch ferulate was synthesized employing a mechanoenzymatic method, specifically based on the twin screw extrusion technique and lipase catalysis. The research then primarily centered on optimizing process parameters and conducting structural analysis. Optimal conditions were determined to be 8.2% ferulic acid addition, 66 °C extrusion temperature, and 3.2% lipase (N435) addition. The enzyme-catalyzed time was 30 s. The degree of substitution for starch ferulate was quantified at 0.005581 under these specific conditions. The presence of C=O bonds in the synthesized starch ferulate proved that the synthesis process was efficient. Additionally, the crystal structure underwent reconstruction. Observations through Scanning Electron Microscopy (SEM) and Confocal Laser Scanning Microscopy (CLSM) demonstrated that the mechanoenzymatic method led to an augmentation in the specific surface area of starch molecules, thereby facilitating the exposure of active sites. This breakthrough underscores the vast potential of mechanoenzymatic techniques to revolutionize the rapid and sustainable synthesis of starch ferulate, marking a pioneering stride in ester synthesis. The insights garnered from this study transcend theory, offering a visionary roadmap for the development and real-world deployment of advanced modified starch esters.
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Ferulic acid (FA) is a natural antibacterial agent rich in plants, FA has excellent antioxidant and antibacterial properties. However, because of its short alkane chain and large polarity, FA is difficult to penetrate the soluble lipid bilayer in the biofilm to enter the cell to play an inhibitory role, limiting its biological activity. To improve the antibacterial activity of FA, with the catalytic condition of Novozym 435, four alkyl ferulic acid esters (FCs) with different alkyl chain lengths were obtained by fatty alcohols (including 1-propanol (C3), 1-hexanol (C6), nonanol (C9), and lauryl alcohol (C12)) modification. The effect of FCs on P. aeruginosa was determined by Minimum inhibitory concentrations (MIC), minimum bactericidal concentrations (MBC), Growth curves, alkaline phosphatase (AKP) activity, crystal violet method, scanning electron microscopy (SEM), membrane potential, PI, cell contents leakage. Results showed that the antibacterial activity of FCs increased after esterification, and the antibacterial activity significantly increased and then decreased with the extension of the alkyl chain of the FCs. Hexyl ferulate (FC6) showed the best antibacterial activities against E. coli and P. aeruginosa (MIC for E. coli was 0.5 mg/ml, MIC for P. aeruginosa was 0.4 mg/ml). And Propyl ferulate (FC3) and FC6 showed the best antibacterial activities S. aureus and B. subtilis (MIC for S. aureus was 0.4 mg/ml, The MIC of B. subtilis was 1.1 mg/ml). In addition, the growth, AKP activity, bacterial biofilm, bacterial cell morphology, membrane potential and cell contents leakage of P. aeruginosa after different FCs were investigated, which found that FCs could damage the cell wall of P. aeruginosa and showed different effects on the P. aeruginosa cell biofilm. FC6 showed the best inhibition on the biofilm formation of P. aeruginosa cells, which caused the surface of P. aeruginosa cells to be rough and wrinkled. Some P. aeruginosa cells showed aggregation and adhesion, even rupture. The membrane hyperpolarization was obvious, which appeared as holes, leading to cell contents leakage (protein and nucleic acid). All these results concluded that the antibacterial activities FCs against foodborne pathogens depended on different fatty alcohol esterification of FA. FC6 showed the best inhibition on P. aeruginosa due to its effect on P. aeruginosa cell walls and biofilms and the leak of the cell contents. This study provides more practical methods and a theoretical basis for giving full play to the bacteriostatic effect of plant FA.
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Esterification of starch was carried out to expand the usefulness of starch for a myriad of industrial applications. Lipase B from Candida antarctica, immobilized on macroporous acrylic resin (Novozym 435), was used for starch esterification in two reaction systems: micro-solvent system and solvent-free system. The esterification of corn starch with palmitic acid in the solvent-free system and micro-solvent system gave a degree of substitution (DS) of 1.04 and 0.0072 respectively. Esterification of corn starch with palmitic acid was confirmed by UV spectroscopy and IR spectroscopy. The results of emulsifying property analysis showed that the starch palmitate with higher DS contributes to the higher emulsifying property (67.6%) and emulsion stability (79.6%) than the native starch (5.3% and 3.9%). Modified starch obtained by esterification that possesses emulsifying properties and has long chain fatty acids, like palmitic acid, has been widely used in the food, pharmaceutical and biomedical applications industries.
Assuntos
Lipase/química , Palmitatos/síntese química , Amido/química , Zea mays/química , Enzimas Imobilizadas , Esterificação , Proteínas FúngicasRESUMO
In this study, the mechanism of ultrasound combined with corn starch granules (CSG) treatment improved the foam properties of whey protein isolates (WPI) and was systematically investigated. The results showed that ultrasound combined with corn starch granules treatment increased foam capacity and stability by 15.38% and 41.40%, respectively. Compared with the control group, corn starch granules enhanced the surface charge (52.38%) and system turbidity (51.43%), which certainly provided the necessary conditions for the improvement of foam stabilization stability. In addition, corn starch granules as microgel particles increased the mechanical properties of the interfacial protein film, thus delaying the instability of foam. This research would provide new insights into the design of new protein-based foam foods in the future food industry.
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Molecular simulation is a new technology to analyze the interaction between molecules. This review mainly summarizes the application of molecular simulation technology in the food industry. This technology has been employed to assess structural changes of biomolecules, the interaction between components, and the mechanism of physical and chemical property alterations. These conclusions provide a deeper understanding of the molecular interaction mechanism in foods, break through the limitations of scientific experiments and avoid blind and time-consuming scientific research. In this paper, the advantages and development trends of molecular simulation technology in the food research field are described. This methodology can be used to contribute to further studies of the mechanism of molecular interactions in food, confirm experimental results and provide new ideas for research in the field of food sciences.
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BACKGROUND: Injecting drugs is associated with a high risk of HIV infection, alongside the risk of a drug overdose and mental health problems. OBJECTIVE: To evaluate the effect of methadone maintenance treatment (MMT) combined with rilpivirine (RPV)-based regimens on drug use of HIV individuals. METHODS: This study was a prospective, open-label, controlled, drug-drug interaction trial at a single center for 24 weeks. Participants on stable MMT were randomly divided into two groups administered RPV/TDF/3TC (RPV group) and EFV/TDF/3TC (EFV group), respectively. Adjustment doses of methadone were monitored for 12 weeks. HIV-1 RNA was used to evaluate the effects of antiretroviral therapy at week 24. Acute opioid withdrawal-, drug craving questionnaire- and MOSHIV scales were used to assess study outcomes. RESULTS: 22 and 18 cases of HIV-infected drug users were recruited in the RPV and EFV groups, respectively. Thirty-one cases had completed monitoring and clinical evaluation at week 24. In the RPV and EFV groups, 32% and 56% of the participants had methadone dose adjustment, respectively, indicating a significantly lower rate in the RPV group. The rates of individuals with HIV RNA levels from 50-500 copies/ml were 94% (RPV group) and 90% (EFV group). The drug craving questionnaire scale scores decreased in both groups. After one week of treatments, acute opioid withdrawal scale scores increased in both groups, with no significant difference between them. CONCLUSION: Concomitant administration of RPV does not significantly affect methadone and could decrease withdrawal symptoms. An RPV-based regimen may be used as first-line treatment in IDUs with HIV infection.
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Fármacos Anti-HIV , Infecções por HIV , HIV-1 , Alcinos , Fármacos Anti-HIV/uso terapêutico , Benzoxazinas , Ciclopropanos , Infecções por HIV/complicações , Infecções por HIV/tratamento farmacológico , Humanos , Metadona/uso terapêutico , Estudos Prospectivos , Rilpivirina/uso terapêutico , Carga ViralRESUMO
PURPOSE: Local anesthetics are used clinically for the control of pain following operation (including gastrointestinal surgery) or for the management of other acute and chronic pain. This study aimed to develop a kind of lipid-polymer hybrid nanoparticles (LPNs), which were constructed using poly(ethylene glycol)-distearoylphosphatidylethanolamine (PEG-DSPE) as the hydrophilic lipid shell and poly-ε-caprolactone (PCL) as the hydrophobic polymeric core. METHODS: Ropivacaine (RPV) was entrapped in the LPNs (RPV-LPNs) and the physicochemical and biochemical properties such as size, zeta potential, drug release, and cytotoxicity were studied. The long-lasting effects and safety aspects of the LPNs were evaluated in vitro and in vivo. RESULTS: The particle size and zeta potential of RPV-LPNs were 112.3±2.6 nm and -33.2±3.2 mV, with an entrapment efficiency (EE) of 90.2%±3.7%. Ex vivo permeation efficiency of LPNs was better than the drug solution. The RPV-LPNs exhibited a long-lasting in vivo anesthesia effect in both rats and mice. CONCLUSION: Considering the low cytotoxicity, the LPNs prepared here could be used as an efficient local anesthetic for the control of pain.
Assuntos
Anestésicos Locais/farmacologia , Lipídeos/química , Nanopartículas/química , Dor/tratamento farmacológico , Polímeros/química , Ropivacaina/uso terapêutico , Células 3T3 , Analgesia , Anestesia , Anestésicos Locais/química , Animais , Morte Celular/efeitos dos fármacos , Portadores de Fármacos/química , Liberação Controlada de Fármacos , Interações Hidrofóbicas e Hidrofílicas , Camundongos , Tamanho da Partícula , Permeabilidade , Fosfatidiletanolaminas/química , Polietilenoglicóis/química , Ratos , Ropivacaina/farmacologia , Eletricidade EstáticaRESUMO
Using a mixed self-assembly method, this research utilized modified Mb-functionalized gold nanoparticles (Mb-AuNPs-MPA) on the gold electrode surface to prepare a biosensor which was applied to detect superoxide anion-free electron mediators. Together with the study on the performance of the sensor, the characteristics of modified nanoclusters were investigated by UV-Vis and FTIR and the electrochemical characteristics of the electrode surface were investigated using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), respectively. It was demonstrated that the charge transfer resistance (Rct) of the modified electrode (Mb-MPA-AuNPs/Au) was 7862 Ω, the exchange current density (i0) was 32.7 µA/cm-2. And a pair of reversible and symmetrical redox peaks appeared after the coordination of Cu2+, and the electrical signal response of Cu2+/Mb-AuNPs-MPA/Au reached the highest. The superoxide anion generated in the basic DMSO system was determined by CV using the modified electrode Cu2+/Mb-AuNPs-MPA/Au. It was discovered that the superoxide anion had a strong disproportionation effect.
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Técnicas Biossensoriais , Nanopartículas Metálicas , Técnicas Eletroquímicas , Eletrodos , Ouro , Imidazóis , Oligopeptídeos , Superóxido DismutaseRESUMO
The lipase-catalyzed enantioselective transesterification of racemic secondary alcohols was studied using vinyl acetate as acyl donor in two imidazolium-based ionic liquids vs. hexane (Scheme), both in the absence and presence of catalytic amounts of organic bases such as triethylamine (Et(3)N) or pyridine. The organic bases generally enhanced both the rate and enantioselectivity of the reaction. Further, the system 1-butyl-3-methyl-1H-imidazolium hexafluorophosphate/Candida antarctica lipase B ([bmim][PF(6)]/CALB) could be readily recycled four times without significant loss in activity or enantioselectivity.
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Álcoois/química , Lipase/metabolismo , Candida/enzimologia , Catálise , EstereoisomerismoRESUMO
A green bioreductive approach with methanobactin was adopted to fabricate bimetallic Au-Pd/Al2O3 catalysts for solvent-free oxidation of glucose to gluconic acid with H2O2 at atmospheric pressure. The catalyst was characterised by diffuse reflectance UV-vis spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction techniques to understand synergistic interactions between Au and Pd. Effects of Au to Pd molar ratio on the catalytic activity of Au-Pd/Al2O3 were investigated. The Au-Pd/Al2O3 catalyst with Au/Pd molar ratio of 0.8:0.2 exhibited excellent catalytic performance. With the catalyst, the oxidation activities of glucose to gluconic acid 2856â mmolâ min-1â g-1 and selectivity 99.6% were attained at 323â K with H2O2. The results indicated the activity and selectivity was affected by the ratio of Au/Pd on the Al2O3. The formation of Au0.8Pd0.2/Al2O3 was favourable for the catalytic reaction.
Assuntos
Óxido de Alumínio/química , Glucose/metabolismo , Ouro/química , Imidazóis/química , Nanopartículas Metálicas/química , Oligopeptídeos/química , Paládio/química , Catálise , Microscopia Eletrônica de Transmissão , Oxirredução , Espectroscopia Fotoeletrônica , Espectrofotometria Ultravioleta , Ressonância de Plasmônio de Superfície , Difração de Raios XRESUMO
The synthesis of L-ascorbyl flurbiprofenate was achieved by esterification and transesterification in nonaqueous organic medium with Novozym 435 lipase as biocatalyst. The conversion was greatly influenced by the kinds of organic solvents, speed of agitation, catalyst loading amount, reaction time, and molar ratio of acyl donor to L-ascorbic acid. A series of solvents were investigated, and tert-butanol was found to be the most suitable from the standpoint of the substrate solubility and the conversion for both the esterification and transesterification. When flurbiprofen was used as acyl donor, 61.0% of L-ascorbic acid was converted against 46.4% in the presence of flurbiprofen methyl ester. The optimal conversion of L-ascorbic acid was obtained when the initial molar ratio of acyl donor to ascorbic acid was 5 : 1. kinetics parameters were solved by Lineweaver-Burk equation under nonsubstrate inhibition condition. Since transesterification has lower conversion, from the standpoint of productivity and the amount of steps required, esterification is a better method compared to transesterification.
Assuntos
Ácido Ascórbico/química , Flurbiprofeno/química , Lipase/química , Enzimas Imobilizadas , Esterificação , Proteínas FúngicasRESUMO
A simple and rapid field-portable colorimetric method for the detection of melamine in liquid milk was reported. Methanobactin (Mb) could reduce Au (III) to Au (0) and mediate the synthesis of gold nanoparticles (Au-NPs). Upon the addition of melamine, melamine interacted with oxazolone ring of Mb, which interrupted the formation of Au-NPs. Melamine could also stimulate the aggregation of formed Au-NPs. In this paper, these characteristics have been used to detect melamine in liquid milk by naked eyes observation with a detection limit of 5.56 × 10(-6)M (0.7 mg/kg). Further, the plasmon absorbance of the formed Au-NPs allowed the quantitative detection of melamine by UV-vis spectrometer. A linear correlation was existed between the absorbance and the melamine concentration ranging from 3.90 × 10(-7)M to 3.97 × 10(-6)M with a correlation coefficient of 0.9685. The detection limit (3σ) obtained by UV-vis spectrum was as low as 2.38 × 10(-7)M (i.e., 0.03 mg/kg).
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Colorimetria/métodos , Ouro/química , Imidazóis/química , Nanopartículas Metálicas/química , Leite/química , Oligopeptídeos/química , Triazinas/química , Animais , Análise de Alimentos/métodos , Contaminação de Alimentos/análiseRESUMO
Methanotrophs have promising applications in the epoxidation of some alkenes and some chlorinated hydrocarbons and in the production of a biopolymer, poly-beta-hydroxybutyrate (poly-3-hydroxybutyrate; PHB). In contrast with methane monooxygenase (MMO) activity and ability of PHB synthesis of four kinds of methanotrophic bacteria Methylosinus trichosporium OB3b, M. trichosporium IMV3011, Methylococcus capsulatus HD6T, Methylomonas sp. GYJ3, and the mixture of the four kinds of strains, M. trichosporium OB3b is the highest of the four in the activity of propene epoxidation (10.72 nmol/min mg dry weight of cell [dwc]), the activity of naphthalene oxidation (22.7 mmol/mg dwc), and ability in synthesis of PHB(11% PHB content in per gram dry weight of cell in 84 h). It could be feasible to improve the MMO activity by mixing four kinds of methanotrophs. The MMO activity dramatically decreased when the cellular PHB accumulated in the second stage. The reason for this may be the dilution of the MMO system in the cells with increasing PHB contents. It has been found that the PHB contents at the level of 1-5% are beneficial to the cells for maintenance of MMO epoxidation activity when enough PHB have been accumulated. Moreover, it was also found that high particulate methane monooxygenase activity may contribute to the synthesis of PHB in the cell, which could be used to improve the yield of PHB in methanotrophs.