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1.
Sensors (Basel) ; 24(13)2024 Jul 05.
Artículo en Inglés | MEDLINE | ID: mdl-39001156

RESUMEN

Optimizing the deployment of roadside units (RSUs) holds great potential for enhancing the delay performance of vehicular ad hoc networks. However, there has been limited focus on devising RSU deployment strategies tailored specifically for highway intersections. In this study, we introduce a novel probabilistic model to characterize events occurring around highway intersections. By leveraging this model, we analytically determine the expected event reporting delays for both highway segments and intersections. Subsequently, we propose an RSU deployment scheme specifically designed for highway intersections, aimed at minimizing the expected event reporting delay. To implement this scheme, we introduce an innovative algorithm named cooperative walking. Through illustrative examples, we demonstrate that our proposed RSU deployment strategy for highway intersections outperforms the commonly employed uniform RSU deployment scheme and the previously proposed balloon method in terms of delay performance.

2.
Food Chem X ; 22: 101405, 2024 Jun 30.
Artículo en Inglés | MEDLINE | ID: mdl-38694543

RESUMEN

This study investigated the effect of inulin with different polymerization degrees (DP), including L-inulin (DP 2-6), M-inulin (DP 10-23) and H-inulin (DP 23-46), on the structural and gelation properties of potato protein isolate (PPI). Results revealed that textural properties (hardness, cohesiveness, springiness and chewiness) and water-holding capacity (WHC) of PPI-inulin composite gels were positively correlated with the inulin DP and addition content at 0-1.5% (w/v), but deteriorated at 2% due to phase separation. The addition of 1.5% H-inulin showed the most significant increment effects on the WHC (18.65%) and hardness (2.84 N) of PPI gel. Furthermore, M-/H-inulin were more effective in increasing the whiteness and surface hydrophobicity, as well as in strengthening hydrogen bonds and hydrophobic interactions than L-inulin. Fourier transform infrared spectroscopy analysis and microstructural observation indicated that inulin with higher DP promoted more generation of ß-sheet structures, and leading to the formation of stronger and finer network structures.

3.
Nat Commun ; 15(1): 1930, 2024 Mar 02.
Artículo en Inglés | MEDLINE | ID: mdl-38431669

RESUMEN

Deep neural networks have revolutionized several domains, including autonomous driving, cancer detection, and drug design, and are the foundation for massive artificial intelligence models. However, hardware neural network reports still mainly focus on shallow networks (2 to 5 layers). Implementing deep neural networks in hardware is challenging due to the layer-by-layer structure, resulting in long training times, signal interference, and low accuracy due to gradient explosion/vanishing. Here, we utilize negative ultraviolet photoconductive light-emitting memristors with intrinsic parallelism and hardware-software co-design to achieve electrical information's optical cross-layer transmission. We propose a hybrid ultra-deep photoelectric neural network and an ultra-deep super-resolution reconstruction neural network using light-emitting memristors and cross-layer block, expanding the networks to 54 and 135 layers, respectively. Further, two networks enable transfer learning, approaching or surpassing software-designed networks in multi-dataset recognition and high-resolution restoration tasks. These proposed strategies show great potential for high-precision multifunctional hardware neural networks and edge artificial intelligence.

4.
Foods ; 12(14)2023 Jul 09.
Artículo en Inglés | MEDLINE | ID: mdl-37509741

RESUMEN

To investigate the impact of frozen storage conditions on the physicochemical properties of soybean protein and explore the underlying mechanisms, this study focused on soybean isolate (SPI), ß-soybean companion globulin (7S), and soybean globulin (11S). The protein solutions were prepared at a concentration of 2% and subjected to freezing for 1 and 5 days. Subsequently, the protein content, physicochemical properties, secondary structure, sulfhydryl content, and chemical interaction forces were assessed and analyzed using UV spectrophotometry, Zeta potential measurements, SDS-PAGE, Fourier infrared spectroscopy, and endogenous fluorescence photoemission spectroscopy. The obtained results revealed that the solubility and total sulfhydryl content of SPI, 7S, and 11S exhibited a decreasing trend with prolonged freezing time. Among them, 11S demonstrated the largest decrease in solubility and total sulfhydryl content, followed by SPI, and 7S the least. During freezing, the aromatic amino acids of SPI, 7S, and 11S molecules were exposed, leading to increased hydrophobicity, protein aggregation, and particle size enlargement, and the structure of the protein changed from disordered structure to ordered structure. After freezing, the polarity of the microenvironment of SPI, 7S, and 11S increased, and their maximum fluorescence emission wavelengths were red-shifted. Notably, the largest red shift of SPI was from 332 nm to 335 nm. As freezing time increased, the contribution of hydrogen bonding increased, while the contribution of hydrophobic interactions decreased. This indicates that freezing affects the hydrophobic interactions, hydrogen bonding, and other chemical forces of the protein. The growth of ice crystals leads to the unfolding of protein molecular chains, exposure of internal hydrophobic groups, enhancement of hydrophobicity, and alters the secondary structure of the protein.

5.
Foods ; 12(22)2023 Nov 09.
Artículo en Inglés | MEDLINE | ID: mdl-38002135

RESUMEN

The kafirin derived from Jin Nuo 3 sorghum underwent a high-hydrostatic-pressure (HHP) treatment of 100, 300, and 600 MPa for 10 min to investigate alterations in its physicochemical attributes. The findings exhibited a reduction in protein solubility, declining from 83% to 62%, consequent to the application of the HHP treatment. However, this treatment did not lead to subunit-specific aggregation. The absorption intensity of UV light diminished, and the peak fluorescence absorption wavelength exhibited a shift from 342 nm to 344 nm, indicating an increased polarity within the amino acid microenvironment. In an aqueous solution, the specific surface area expanded from 294.2 m2/kg to 304.5 m2/kg, while the average particle-size value in a 70% ethanol solution rose to 26.3 nm. Conversely, the zeta-potential value decreased from 3.4 mV to 1.3 mV, suggesting a propensity for aggregation in ethanol solutions. A notable rise in the intermolecular ß-sheet content to 21.06% was observed, along with a shift in the peak denaturation temperature from 76.33 °C to 86.33 °C. Additionally, the content of disulfide bonds increased to 14.5 µmol/g. Collectively, the application of the HHP treatment not only enhanced the thermal stability but also induced a more ordered secondary structure within the kafirin.

6.
Talanta ; 265: 124802, 2023 Dec 01.
Artículo en Inglés | MEDLINE | ID: mdl-37329751

RESUMEN

In this paper, an analysis method for chlorpyrifos (CPF) in cereal samples was proposed using dispersive liquid‒liquid microextraction combined with an enzyme-linked immunosorbent assay. In the dispersive liquid‒liquid microextraction, deep eutectic solvents and fatty acids were used as solvents to extract, purify, and concentrate CPF in cereals. In the enzyme-linked immunosorbent assay, gold nanoparticles were utilized to enrich and conjugate more antibodies and horseradish peroxidase, while magnetic beads were used as solid supports to amplify the signal and shorten the detection time of CPF. The linearity range was 0.002-1 µg kg-1, and the limit of detection was 0.0006 µg kg-1. The extraction recoveries were 86.7-99.9% with a relative standard deviation of less than 7.0%. The proposed method was successfully used to analyze CPF in cereal samples (rice, wheat, maize, and millet) and has prospects for the pretreatment and detection of CPF residues in other food samples.


Asunto(s)
Cloropirifos , Microextracción en Fase Líquida , Nanopartículas del Metal , Grano Comestible , Microextracción en Fase Líquida/métodos , Oro , Solventes/química , Ensayo de Inmunoadsorción Enzimática , Límite de Detección
7.
Talanta ; 265: 124831, 2023 Dec 01.
Artículo en Inglés | MEDLINE | ID: mdl-37339538

RESUMEN

To determine parathion in cereals, hydrophilic and hydrophobic deep eutectic solvents (DESs) were used by digital image colorimetry with smartphones. In the solid-liquid extraction part, hydrophilic DESs were used as extractants to extract parathion from cereals. In the liquid-liquid microextraction part, hydrophobic DESs dissociated into terpineol and tetrabutylammonium bromide in situ. The dissociated hydrophilic tetrabutylammonium ions reacted with parathion extracted in hydrophilic DESs under alkaline conditions to produce a yellow product, which was extracted and concentrated by dispersed organic phase terpinol. Digital image colorimetry integrated with the use of a smartphone was used for quantitative analysis. The limit of detection and quantification were 0.003 mg kg-1 and 0.01 mg kg-1, respectively. The recoveries for parathion were 94.8-106.2% with a relative standard deviation less than 3.6%. The proposed method was applied to analyze parathion in cereal samples: the method has the potential to be applied to pesticide residue analysis in food products.


Asunto(s)
Microextracción en Fase Líquida , Paratión , Solventes/química , Grano Comestible , Teléfono Inteligente , Disolventes Eutécticos Profundos , Colorimetría , Microextracción en Fase Líquida/métodos , Límite de Detección
8.
Acta Crystallogr D Biol Crystallogr ; 68(Pt 2): 186-93, 2012 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-22281748

RESUMEN

Multi-copper oxidases constitute a family of proteins that are capable of coupling the one-electron oxidation of four substrate equivalents to the four-electron reduction of dioxygen to two molecules of water. The main catalytic stages occurring during the process have already been identified, but several questions remain, including the nature of the protonation events that take place during the reductive cleavage of dioxygen to water. The presence of a structurally conserved acidic residue (Glu498 in CotA laccase from Bacillus subtilis) at the dioxygen-entrance channel has been reported to play a decisive role in the protonation mechanisms, channelling protons during the reduction process and stabilizing the site as a whole. A second acidic residue that is sequentially conserved in multi-copper oxidases and sited within the exit channel (Asp116 in CotA) has also been identified as being important in the protonation process. In this study, CotA laccase has been used as a model system to assess the role of Asp116 in the reduction process of dioxygen to water. The crystal structures of three distinct mutants, D116E, D116N and D116A, produced by site-saturation mutagenesis have been determined. In addition, theoretical calculations have provided further support for a role of this residue in the protonation events.


Asunto(s)
Ácido Aspártico/metabolismo , Bacillus subtilis/enzimología , Lacasa/metabolismo , Oxígeno/metabolismo , Protones , Agua/metabolismo , Ácido Aspártico/química , Ácido Aspártico/genética , Bacillus subtilis/química , Bacillus subtilis/genética , Bacillus subtilis/metabolismo , Cristalografía por Rayos X , Lacasa/química , Lacasa/genética , Modelos Moleculares , Mutación , Oxidación-Reducción , Conformación Proteica
9.
Spectrochim Acta A Mol Biomol Spectrosc ; 266: 120412, 2022 Feb 05.
Artículo en Inglés | MEDLINE | ID: mdl-34597870

RESUMEN

A deep eutectic solvent (DES)-based extraction method is established to facilitate the determination of methomyl in grain via enzyme inhibition fluorescence. The environmentally-friendly DES was synthesized from proline and ethylene glycol and used as a green replacement for traditional extraction solvents that are generally toxic. The DES was added to grain samples and vortex extraction of methomyl, the supernatant was then collected for fluorescence detection. Biomass carbon quantum dots (CQDs) synthesized from millet were used as fluorescent probes. Acetylcholinesterase catalyzes the hydrolysis of acetylthiocholine iodide to thiocholine. The positively-charged thiocholine interacts electrostatically with the negatively-charged quantum dots resulting in the quenching of their fluorescent emission. The pesticide extract solution blocks the enzyme activity and thus recovers the fluorescent from the quantum dots. The fluorescence response was correlated with the amount of methomyl residue in the grain over the range 0.01 to 5 mg kg-1. The limit of detection was found to be 0.003 mg kg-1, and the limit of quantification 0.01 mg kg-1. Recoveries of 86.5% to 107.8% were obtained using real samples, including millet, rice, wheat, and barley, with a relative standard deviation of less than 3.8%. The method is efficient and convenient and has good application prospects for extracting and detecting pesticides in grain samples.


Asunto(s)
Metomil , Puntos Cuánticos , Acetilcolinesterasa , Grano Comestible , Límite de Detección , Solventes
10.
Foods ; 12(1)2022 Dec 25.
Artículo en Inglés | MEDLINE | ID: mdl-36613314

RESUMEN

To explore the effect of micronization on the structural, functional, and antioxidant properties of wheat bran, wheat bran with mean particle size (D50) of 46.08, 34.29, 26.51, 26.35, and 26.05 µm were prepared by using an ultrafine pulverizer under different rolling frequencies (0, 6, 9, 12, and 15 times). The main chemical components and structural, functional, and antioxidant properties of the wheat bran were compared and a correlation analysis was conducted. As the D50 of the wheat bran decreased from 46.08 µm to 26.05 µm, the micromorphology exhibited the destruction of the bundle structure, which is formed by starch and fiber, during which the starch particles peeled off, the fiber fragments destructed, and some of the slim fiber fragments attached to the surfaces of the starch granules. According to the X-ray diffraction pattern, part of the crystalline structure was transformed into an amorphous structure and the crystallization index decreased from 13.08% to 3.95%. According to the near-infrared spectrum, more active groups, such as the hydroxyl group, were exposed; however, no new groups were generated. These structural changes accordingly caused changes in the chemical components, functional properties, and antioxidant properties of the wheat bran. Specifically, the protein, total phenols, total flavonoids, and fatty acid content increased by 6.72%, 23.47%, 19.07%, and 172.88%, respectively. The lipase activity, antioxidant activity in vitro (DPPH• scavenging activity, ABTS+• scavenging activity, and ferric reducing antioxidant power), and the water-holding, cholesterol-adsorption, sodium nitrite-adsorption, and cation-exchange capacities, were enhanced to some extent. The oil-holding capacity decreased from 3.01 g/g to 1.32 g/g. The swelling capacity decreased first and then increased and the swelling capacity of the wheat bran with a D50 of 34.29 µm was the lowest (3.62 mL/g). Therefore, the micronization could be used as a pretreatment method to improve the functional and antioxidant properties of wheat bran; however, the optimal particle size of wheat bran is based on the function of the product.

11.
Foods ; 11(19)2022 Sep 29.
Artículo en Inglés | MEDLINE | ID: mdl-36230104

RESUMEN

Jinqiao II, a newly cultivated variety of tartary buckwheat (Fagopyrum tataricum), has been reported to exhibit a higher yield and elevated levels of functional compounds compared to traditional native breeds. We aimed to investigate the potential of Jinqiao II tartary buckwheat to alleviate lipid metabolism disorders by detecting serum biochemistry, pathological symptoms, gene expression profiling, and gut microbial diversity. C57BL/6J mice were provided with either a normal diet; a high-fat diet (HFD); or HFD containing 5%, 10%, and 20% buckwheat for 8 weeks. Our results indicate that Jinqiao II tartary buckwheat attenuated HFD-induced hyperlipidemia, fat accumulation, hepatic damage, endotoxemia, inflammation, abnormal hormonal profiles, and differential lipid-metabolism-related gene expression at mRNA and protein levels in response to the dosages, and high-dose tartary buckwheat exerted optimal outcomes. Gut microbiota sequencing also revealed that the Jinqiao II tartary buckwheat elevated the level of microbial diversity and the abundance of advantageous microbes (Alistipes and Alloprevotella), lowered the abundance of opportunistic pathogens (Ruminococcaceae, Blautia, Ruminiclostridium, Bilophila, and Oscillibacter), and altered the intestinal microbiota structure in mice fed with HFD. These findings suggest that Jinqiao II tartary buckwheat might serve as a competitive candidate in the development of functional food to prevent lipid metabolic abnormalities.

12.
ACS Nano ; 16(11): 19155-19164, 2022 11 22.
Artículo en Inglés | MEDLINE | ID: mdl-36269153

RESUMEN

As one of the most common synergies between the exteroceptors and proprioceptors, the synergy between visual and vestibule enables the human brain to judge the state of human motion, which is essential for motion recognition and human self-protection. Hence, in this work, an artificial motion sensory system (AMSS) based on artificial vestibule and visual is developed, which consists of a tribo-nanogenerator (TENG) as a vestibule that can sense rotation and synaptic transistor array as retina. The principle of temporal congruency has been successfully realized by multisensory input. In addition, pattern recognition results show that the accuracy of multisensory integration is more than 15% higher than that of single sensory. Moreover, due to the rotation recognition and visual recognition functions of AMSS, we realized multimodal information recognition including angles and numbers in the spiking correlated neural network (SCNN), and the accuracy rate reached 89.82%. Besides, the rapid self-protection of a human was successfully realized by AMSS in the case of simulated amusement rides, and the reaction time of multiple motion sensory integration is only one-third of that of a single vestibule. The development of AMSS based on the synergy of simulated vision and vestibule will show great potential in neural robot, artificial limbs, and soft electronics.


Asunto(s)
Vestíbulo del Laberinto , Humanos , Rotación , Movimiento (Física) , Visión Ocular , Redes Neurales de la Computación , Encéfalo
13.
Antioxidants (Basel) ; 11(12)2022 Dec 14.
Artículo en Inglés | MEDLINE | ID: mdl-36552666

RESUMEN

Foxtail millet has been traditionally considered to possess gastroprotective effects, but studies evaluating its use as a treatment for gastric ulcers are lacking. Here, we assessed the antiulcer effects of foxtail millet protein hydrolysate (FPH) and explored its mechanism by using blocking agents. In a mouse model of ethanol-induced gastric ulcers, pretreatment with FPH reduced the ulcerative lesion index, downregulated the expression of inflammatory cytokines in the gastric tissue, increased the activity of antioxidant enzymes, and improved the oxidative status. FPH increased constitutive the activity of nitric oxide synthase (cNOS), NO levels, and mucin expression in gastric mucosa, and inhibited the activation of the ET-1/PI3K/Akt pathway. In a mouse model of pyloric ligation-induced gastric ulcers, FPH inhibited gastric acid secretion and decreased the activity of gastric protease. Pretreatment of mice with the sulfhydryl blocker NEM and the NO synthesis inhibitor L-NAME abolished the gastroprotective effect of FPH, but not the KATP channel blocker glibenclamide and the PGE2 synthesis blocker indomethacin. Among the peptides identified in FPH, 10 peptides were predicted to have regulatory effects on the gastric mucosa, and the key sequences were GP and PG. The results confirmed the gastroprotective effect of FPH and revealed that its mechanism was through the regulation of gastric mucosal mucus and NO synthesis. This study supports the health effects of a millet-enriched diet and provides a basis for millet protein as a functional food to improve gastric ulcers and its related oxidative stress.

14.
Artículo en Inglés | MEDLINE | ID: mdl-21206041

RESUMEN

PpAzoR, an FMN-dependent NADPH azoreductase from Pseudomonas putida MET94, has been crystallized using the sitting-drop vapour-diffusion technique. The crystals diffracted to 1.6 Šresolution using synchrotron radiation and belonged to the orthorhombic space group F222, with unit-cell parameters a=72.1, b=95.5, c=146.1 Å. Data sets were collected from the native protein to 2.2 Šresolution using in-house equipment and to 1.6 Šresolution using synchrotron radiation and the three-dimensional structure was determined by the molecular-replacement method.


Asunto(s)
Proteínas Bacterianas/química , NADH NADPH Oxidorreductasas/química , Pseudomonas putida/enzimología , Cristalización , Cristalografía por Rayos X , Datos de Secuencia Molecular , Nitrorreductasas , Conformación Proteica
15.
Sci Rep ; 11(1): 21383, 2021 11 01.
Artículo en Inglés | MEDLINE | ID: mdl-34725393

RESUMEN

Electromagnetic spectrum detection is the basis of the next generation wireless communication technology. Wireless signal identification is an important part of electromagnetic spectrum detection and management activities. This paper proposes to extract the distribution features of different modulated signals from the signal I/Q data. A two-dimensional gradient matrix is used to describe the characteristics of the signal classification. The minimum gradient cumulative distance (GCD) estimate between the sample and the model is used as the decision criterion for the signal classification. According to the result of the confusion matrix, the weight of the model is adjusted. Experiments show that the recognition rate of the modulated signal mentioned in this paper can reach 82.75%. The I/Q data sample was extracted under actual engineering conditions involving random noise, and the recognition rate dropped to approximately 79%. Based on the initial model gradient matrix, a reasonable algorithm is set to adjust the weight of the model, which can effectively improve the recognition rate of the modulated signal.

16.
Food Chem ; 337: 127971, 2021 Feb 01.
Artículo en Inglés | MEDLINE | ID: mdl-32916534

RESUMEN

This research used a digital image colorimetry (DIC) method to detect carbaryl in food samples using effervescence-assisted liquid phase microextraction based on solidification of switchable hydrophilicity solvent combined with a microfluidic thread-based analytical device (EA-LPME-SSHS-µTAD). 1-naphthol, the hydrolysate of carbaryl, was extracted into octanoic acid by the adjustment of pH values of the sample solution and separated through solidification in an ice bath. Then 1-naphthol contained in the extracted solution was coupled with 4-methoxybenzenediazonlum tetrafluoroborate (MBDF) fixed on the µTAD to produce tangerine compounds. The inherent colour variation was captured by a smartphone and processed to calculate the intensity (I). Under the optimal conditions, the limit of quantification was within 0.020-0.027 mg kg-1. The recovery was varied in the range from 92.3% to 105.9% with a relative standard deviation (RSD) below 5%. The developed method provides an alternative strategy to extract and detect pesticides for food samples.


Asunto(s)
Carbaril/análisis , Colorimetría/métodos , Análisis de los Alimentos , Microextracción en Fase Líquida/métodos , Procesamiento de Imagen Asistido por Computador/métodos , Dispositivos Laboratorio en un Chip
17.
Anal Methods ; 13(5): 636-641, 2021 02 07.
Artículo en Inglés | MEDLINE | ID: mdl-33491682

RESUMEN

This work presents a novel and green analytical procedure involving a deep eutectic solvent-based dispersive liquid-liquid microextraction with solidification of floating organic droplets (DES-DLLME-SFOD) followed by HPLC to measure three pyrethroids (bifenthrin, ß-cypermethrin, and deltamethrin) in cereal samples. Firstly, a low-density hydrophobic DES was synthesized from thymol and octanoic acid in the molar ratio of 1/4 and this was applied as a green extraction solvent in the DLLME procedure to avoid the use of a toxic extractant. After centrifugation and placing it on an ice bath, it is transformed into a solid phase on the top of the sample solution to reduce the loss of extractant, conducive to convenient collection thereafter. This procedure required the optimal conditions (including the type, proportion, and amount of DES as the extractant, the volume of the dispersant acetonitrile, the amount of salt, and the pH value) to be evaluated. Under optimized variates, the proposed method provided good linearity with a correlation coefficient greater than 0.997 and limits of quantification within the range of 6.6-8.9 µg kg-1. The recoveries of pyrethroids in corn, wheat, barley, and oats were 75.6-87.2%, and the relative standard deviation was less than 3.6%. The method, therefore, offers a green, efficient, and convenient approach for the determination of pesticides in cereals.


Asunto(s)
Microextracción en Fase Líquida , Piretrinas , Cromatografía Líquida de Alta Presión , Grano Comestible , Solventes
18.
BMC Struct Biol ; 10: 28, 2010 Sep 07.
Artículo en Inglés | MEDLINE | ID: mdl-20822511

RESUMEN

BACKGROUND: Laccases are enzymes that couple the oxidation of substrates with the reduction of dioxygen to water. They are the simplest members of the multi-copper oxidases and contain at least two types of copper centres; a mononuclear T1 and a trinuclear that includes two T3 and one T2 copper ions. Substrate oxidation takes place at the mononuclear centre whereas reduction of oxygen to water occurs at the trinuclear centre. RESULTS: In this study, the CotA laccase from Bacillus subtilis was used as a model to understand the mechanisms taking place at the molecular level, with a focus in the trinuclear centre. The structures of the holo-protein and of the oxidised form of the apo-protein, which has previously been reconstituted in vitro with Cu(I), have been determined. The former has a dioxygen moiety between the T3 coppers, while the latter has a monoatomic oxygen, here interpreted as a hydroxyl ion. The UV/visible spectra of these two forms have been analysed in the crystals and compared with the data obtained in solution. Theoretical calculations on these and other structures of CotA were used to identify groups that may be responsible for channelling the protons that are needed for reduction of dioxygen to water. CONCLUSIONS: These results present evidence that Glu 498 is the only proton-active group in the vicinity of the trinuclear centre. This strongly suggests that this residue may be responsible for channelling the protons needed for the reduction. These results are compared with other data available for these enzymes, highlighting similarities and differences within laccases and multicopper oxidases.


Asunto(s)
Bacillus subtilis/enzimología , Lacasa/química , Lacasa/metabolismo , Modelos Moleculares , Oxígeno/metabolismo , Conformación Proteica , Protones , Cobre/metabolismo , Cristalización , Oxidación-Reducción , Espectrofotometría Ultravioleta
19.
Food Res Int ; 129: 108879, 2020 03.
Artículo en Inglés | MEDLINE | ID: mdl-32036935

RESUMEN

The volatile aroma compounds of traditional Chinese rose vinegar were identified by headspace solid-phase micro extraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) and GC-MS-olfactometry (GC-MS-O), and the metabolites were identified by silylation-GC-MS in this study. A total of 48 and 76 kinds of flavors and metabolites, respectively were detected in this study. Quantitative analysis showed that aldehydes and acids were present in relatively high amounts. Furthermore, the data colleted by the calculated odor activity values (OAVs) suggested that aldehydes are likely to contribute greatly to the aroma of traditional Chinese rose vinegar, especially, nonanal (OAV: 133, rose), 3-methyl-butanal (OAV: 57, apple-like), decanal (OAV: 23, orange peel), heptanal (OAV: 17, fruity), and dodecanal (OAV: 4-9, violet scents). Moreover, among the detected nonvolatile acids, 14 kinds of hydroxy acids, such as lactic acid, citric acid, 3-phenyllactic acid (PLA) and d-gluconic acid were detected in rose vinegar. The acids provide a well buffer system, not only greatly reduce the irritation of acetic acid, but also improve the flavor of rose vinegar. This study suggests that the fragrance and sour notes in rose vinegar are from aldehydes and hydroxy acids.


Asunto(s)
Ácido Acético/análisis , Aldehídos/química , Aromatizantes/química , Hidroxiácidos/química , Rosa/química , Cromatografía de Gases y Espectrometría de Masas/métodos , Humanos , Odorantes , Gusto
20.
Biochem J ; 412(2): 339-46, 2008 Jun 01.
Artículo en Inglés | MEDLINE | ID: mdl-18307408

RESUMEN

In the present study the CotA laccase from Bacillus subtilis has been mutated at two hydrophobic residues in the vicinity of the type 1 copper site. The mutation of Leu(386) to an alanine residue appears to cause only very subtle alterations in the properties of the enzyme indicating minimal changes in the structure of the copper centres. However, the replacement of Ile(494) by an alanine residue leads to significant changes in the enzyme. Thus the major visible absorption band is upshifted by 16 nm to 625 nm and exhibits an increased intensity, whereas the intensity of the shoulder at approx. 330 nm is decreased by a factor of two. Simulation of the EPR spectrum of the I494A mutant reveals differences in the type 1 as well as in the type 2 copper centre reflecting modifications of the geometry of these centres. The intensity weighted frequencies , calculated from resonance Raman spectra are 410 cm(-1) for the wild-type enzyme and 396 cm(-1) for the I494A mutant, indicating an increase of the Cu-S bond length in the type 1 copper site of the mutant. Overall the data clearly indicate that the Ile(494) mutation causes a major alteration of the structure near the type 1 copper site and this has been confirmed by X-ray crystallography. The crystal structure shows the presence of a fifth ligand, a solvent molecule, at the type 1 copper site leading to an approximate trigonal bipyramidal geometry. The redox potentials of the L386A and I494A mutants are shifted downwards by approx. 60 and 100 mV respectively. These changes correlate well with decreased catalytic efficiency of both mutants compared with the wild-type.


Asunto(s)
Bacillus subtilis/enzimología , Cobre/química , Lacasa/química , Lacasa/genética , Leucina/metabolismo , Mutación , Conformación Proteica , Proteínas Bacterianas , Cobre/metabolismo , Cristalografía por Rayos X , Isoleucina/metabolismo , Lacasa/metabolismo , Modelos Moleculares , Datos de Secuencia Molecular , Oxidación-Reducción , Análisis Espectral
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