RESUMO
Efficient charge carrier transport characteristics are critical to achieving the excellent performance of metal-oxide semiconductor gas sensors. Herein, SnO2/CeO2 heterojunction layered nanosheets with abundant oxygen vacancies were successfully synthesized through a simple solvothermal assisted high-temperature calcination method. The synergistic effect of oxygen vacancies and heterojunctions promoting the charge carrier transport properties at the SnO2/CeO2 interface for the enhanced sensing properties of triethylamine (TEA) was highlighted. As a result, the optimized SnO2/CeO2 exhibits improved gas sensing performance at 173 °C to 50 ppm of TEA. These include high response (205), excellent selectivity, low detection limit, and good long-term stability. This enhanced gas sensing property of SnO2/CeO2 is mainly attributed to the fact that the heterojunction and oxygen vacancies act as dual active sites synergistically inducing electron transfer, thereby effectively modulating the transport properties of the interfacial charge carriers, and thus facilitate the surface reactions efficiently. In this work, the dual-engineering strategy of synergistic interaction of heterojunction and oxygen vacancies can provide new perspectives for the design of advanced gas sensing materials.
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Nanozymes, enzyme-mimicking nanomaterials, have attracted increasing attention due to their low cost, high stability, and catalytic ability compared with natural enzymes. However, the catalytic efficiency of the nanozymes is still relatively low, and catalytic reaction mechanisms remain unclear. To address these issues, herein we prepared nitrogen-riched and sulfur-codoped nano hollow carbons (N/S-HCS) using a green and useful template of CaCO3. N/S-HCS exhibits enhanced oxidase-like activity and catalytic kinetic performance. It could directly oxidize the colorless 3,3',5,5'-tetramethylbenzidine (TMB) to the heavy blue colored ox-TMB without H2O2. The maximum reaction rate (Vmax) is 186.7 × 10-8 M·s-1, and Michaelis-Menten constant (Km) is 0.162 mM. DFT results show that N and S codoping could work synergistically to provide more active sites, resulting in the superior ability to adsorb oxygen and enhanced catalytic activity. Meantime, we develop a multispectral characterization strategy to unravel catalytic reaction mechanisms about N/S-HCS. It successfully induces the generation of superoxide (â¢O2-) and hydroxyl (â¢OH) during the colorimetric reaction which are the key intermediate products of the catalytic reaction. Furthermore, N/S-HCS increased the cellular reactive oxygen species level significantly and induced bacteriostasis to more than 95% of Escherichia coli.
Assuntos
Peróxido de Hidrogênio , Oxirredutases , Benzidinas , Carbono , Escherichia coli , Oxigênio , EnxofreRESUMO
Immobilized angiotensin-converting enzyme (ACE) is a promising material for the rapid screening of antihypertensive drugs, but the nonspecific adsorption is a serious problem in separation processes involving complex biological products. In this study, triblock copolymers with dopamine (DA) block as anchors and PEG block as the main body (DA-PEGx-DA) were attached to an immobilized ACE (ACE@mZIF-8/PDA, AmZP) surface via the "grafting to" strategy which endowed them with anti-nonspecific adsorption. The influence of DA-PEGx-DA chain length on nonspecific adsorption was confirmed. The excellent specificity and reusability of the obtained ACE@mZIF-8/PDA/DA-PEG5000-DA (AmZPP5000) was validated by screening two known ACE inhibitory peptides Val-Pro-Pro (VPP, competitive inhibitory peptides of ACE) and Gly-Met-Lys-Cys-Ala-Phe (GF-6, noncompetitive inhibitory peptides of ACE) from a mixture containing active and inactive compounds. These results demonstrate that anchored polymer loops are effective for high-recognition selectivity and AmZPP5000 is a promising compound for the efficient separation of ACE inhibitors in biological samples.
Assuntos
Inibidores da Enzima Conversora de Angiotensina , Peptídeos , Peptídeos/farmacologia , Peptídeos/química , Inibidores da Enzima Conversora de Angiotensina/farmacologia , Inibidores da Enzima Conversora de Angiotensina/química , Anti-Hipertensivos/química , Peptidil Dipeptidase A , AngiotensinasRESUMO
Angiotensin-I-converting enzyme (ACE) inhibitory peptides derived from marine organism have shown a blood pressure lowering effect with no side effects. A new affinity medium of Fe3O4@ZIF-90 immobilized ACE (Fe3O4@ZIF-90-ACE) was prepared and used in the purification of ACE inhibitory peptides from Wakame (Undaria pinnatifida) protein hydrolysate (<5 kDa). The Fe3O4@ZIF-90 nanoparticles were prepared by a one-pot synthesis and crude ACE extract from pig lung was immobilized onto it, which exhibited excellent stability and reusability. A novel ACE inhibitory peptide, KNFL (inhibitory concentration 50, IC50 = 225.87 µM) was identified by affinity purification using Fe3O4@ZIF-90-ACE combined with reverse phase-high performance liquid chromatography (RP-HPLC) and MALDI-TOF mass spectrometry. Lineweaver-Burk analysis confirmed the non-competitive inhibition pattern of KNFL, and molecular docking showed that it bound at a non-active site of ACE via hydrogen bonds. This demonstrates that affinity purification using Fe3O4@ZIF-90-ACE is a highly efficient method for separating ACE inhibitory peptides from complex protein mixtures and the purified peptide KNFL could be developed as a functional food ingredients against hypertension.
Assuntos
Inibidores da Enzima Conversora de Angiotensina/isolamento & purificação , Cromatografia de Afinidade , Peptídeos/isolamento & purificação , Peptidil Dipeptidase A/metabolismo , Undaria/metabolismo , Inibidores da Enzima Conversora de Angiotensina/metabolismo , Inibidores da Enzima Conversora de Angiotensina/farmacologia , Cromatografia Líquida de Alta Pressão , Cromatografia de Fase Reversa , Ligação de Hidrogênio , Hidrólise , Simulação de Acoplamento Molecular , Peptídeos/metabolismo , Peptídeos/farmacologia , Ligação Proteica , Conformação Proteica , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por MatrizRESUMO
In this work, a visible light-driven ternary heterojunction photocatalyst, CdS/Bi2WO6/ZnO, was synthesized using hydrothermal, ultrasonic dispersion, and deposition precipitation methods. The results show that photocatalysts with flower-like heterostructures were obtained, which could efficiently separate electron-hole pairs, and the photocatalytic activity was thereby significantly enhanced. Furthermore, CdS/Bi2WO6/ZnO and polyvinylidene fluoride (PVDF) were used to fabricate hybrid membranes via a phase-conversion method. The samples were characterized using SEM, TEM, EDX, XRD, DRS, XPS, PL, and N2 adsorption-desorption isotherms, and the transient photocurrent response. The photocatalytic activity of the hybrid membrane was evaluated, and 92.58% of the nitrite was converted into non-toxic substances within 4 h under simulated sunlight irradiation. This result indicated that the photocatalyst exhibited a good photocatalytic activity after immobilization. The possible mechanism was elucidated by studying the product during the photocatalytic degradation, and the effects of different pH values, electron scavengers, and hole scavengers on the photocatalytic performance were further investigated.
Assuntos
Óxido de Zinco , Luz , Nitritos , Polivinil , ÁguaRESUMO
A facile and versatile microwave-assisted and shell-confined Kirkendall diffusion strategy is used to fabricate ultrasmall hollow nanoparticles by modulating the growth and thermal conversion of metal-organic framework (MOF) nanocrystals on graphene. This method involves that the adsorption of microwave by graphene creates a high-energy environment in a short time to decompose the inâ situ grown MOF nanocrystals into well-dispersed uniform core-shell nanoparticles with ultrasmall size. Upon a shell-confined Kirkendall diffusion process, hollow nanoparticles of multi-metal oxides, phosphides, and sulfides with the diameter below 20â nm and shell thickness below 3â nm can be obtained for the first time. Ultrasmall hollow nanostructures such as Fe2O3 can promote much faster charge transport and expose more active sites as well as migrate the volume change stress more efficiently than the solid and large hollow counterparts, thus demonstrating remarkable lithium-ion storage performance.
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Angiotensin-I-converting enzyme (ACE) inhibitory peptides derived from natural products have shown a blood pressure lowering effect with no side effects. In this study, two novel ACE inhibitory peptides (His-Leu-His-Thr, HLHT and Gly-Trp-Ala, GWA) were purified from pearl oyster (Pinctada fucata martensii) meat protein hydrolysate with alkaline protease by ultrafiltration, polyethylene glycol methyl ether modified immobilized metal ion affinity medium, and reverse-phase high performance liquid chromatography. Both peptides exhibited high ACE inhibitory activity with IC50 values of 458.06 ± 3.24 µM and 109.25 ± 1.45 µM, respectively. Based on the results of a Lineweaver-Burk plot, HLHT and GWA were found to be non-competitive inhibitor and competitive inhibitor respectively, which were confirmed by molecular docking. Furthermore, the pearl oyster meat protein hydrolysate exhibited an effective antihypertensive effect on SD rats. These results conclude that pearl oyster meat protein is a potential resource of ACE inhibitory peptides and the purified peptides, HLHT and GWA, can be exploited as functional food ingredients against hypertension.
Assuntos
Inibidores da Enzima Conversora de Angiotensina/química , Inibidores da Enzima Conversora de Angiotensina/farmacologia , Peptídeos/química , Peptídeos/farmacologia , Peptidil Dipeptidase A/metabolismo , Pinctada/química , Hidrolisados de Proteína/química , Animais , Anti-Hipertensivos/química , Anti-Hipertensivos/farmacologia , Cromatografia Líquida de Alta Pressão/métodos , Hipertensão/tratamento farmacológico , Masculino , Carne , Simulação de Acoplamento Molecular , Pinctada/metabolismo , Hidrolisados de Proteína/metabolismo , Ratos , Ratos Sprague-Dawley , Ultrafiltração/métodosRESUMO
BACKGROUND: Low concentration NaHCO3 (ca. 12 mM) had been demonstrated to be an excellent carbon source for industrially important green alga Chlorella vulgaris and high concentration NaHCO3 (e.g. 160 mM) had been shown to be capable of controlling protozoa and stimulating lipid accumulation of another green alga, i.e., Neochloris oleoabundans. Furthermore, little was known about the mechanisms of the effects of NaHCO3 on microalgae. Thorough studies on the effects of high NaHCO3 on C. vulgaris and their mechanisms were therefore warranted. METHODS: We systematically compared the cell growth, lipid production, and cell morphology of the industrially important C. vulgaris in 160 mM NaHCO3 or 160 mM NaCl media at different pH levels. These data allowed us to analyze the effects of total dissolved inorganic carbon (DIC) and individual DIC species on C. vulgaris. Cell growth of C. vulgaris at a range of concentrations at 160 mM or lower was also studied. RESULTS: Cellular lipid cell content of 494 mg g-1 and lipid productivity of 44.5 mg L-1 day-1 were obtained at 160 mM NaHCO3 and pH 9.5. High concentration NaHCO3 (e.g. 160 mM) was inhibitive to cell growth but stimulating to lipid accumulation and caused unicellular C. vulgaris to transfer to colonial cells. Increasing pH in the range of 7.5-9.5 caused increasing inhibition to cell growth in 160 mM NaCl. Whereas the optimal pH for cell growth was 8.5 for 160 mM NaHCO3 cultures. Comparative experiments with 0-160 mM NaHCO3 indicate that 10 mM was the optimal concentration and increasing NaHCO3 from 10 to 160 mM caused increasing inhibition to cell growth. CONCLUSIONS: High concentration DIC was inhibitor to cell growth but stimulator to lipid accumulation of C. vulgaris. It caused unicellular C. vulgaris to transform to colonial cells. Results suggest that high concentration of a particular DIC species, i.e., dCO2, was the primary stress responsible for cell growth inhibition. Where CO32- was likely the DIC species responsible for lipid stimulation of C. vulgaris. Furthermore, we propose that the colony formation at high DIC conditions was employed by C. vulgaris to mitigate the stress by minimizing cell exposure to unfavorable environment.
Assuntos
Chlorella vulgaris/efeitos dos fármacos , Chlorella vulgaris/crescimento & desenvolvimento , Lipídeos/biossíntese , Bicarbonato de Sódio/farmacologia , Biocombustíveis , Biomassa , Carbono/análise , Chlorella vulgaris/metabolismo , Meios de Cultura/análise , Meios de Cultura/química , Concentração de Íons de HidrogênioRESUMO
Lizard fish protein hydrolysates (LFPH) were prepared from Lizard fish (Saurida elongata) proteins possessing powerful angiotensin I converting enzyme (ACE) inhibitory activity and the fraction (LFPH-I) with high ACE inhibitory activity was obtained through ultrafiltration. The active Fraction (F2) was isolated from LFPH-I using immobilized metal affinity chromatography (IMAC-Ni2+). Analysis of amino acid levels revealed that F2 eluted from IMAC was enriched in Met, His, Tyr, Pro, Ile, and Leu compared to the crude peptide LFPH-I. F2 with the high ACE inhibitory activity (IC50 of 0.116 mg·mL-1) was further separated by a reverse-phase column to yield a novel ACE inhibitory peptide with IC50 value of 52 µM. The ACE inhibitory peptide was identified as Arg-Tyr-Arg-Pro, RYRP. The present study demonstrated that IMAC may be a useful tool for the separation of ACE inhibitory peptides from protein hydrolysate.
Assuntos
Inibidores da Enzima Conversora de Angiotensina/isolamento & purificação , Cromatografia de Afinidade/métodos , Proteínas de Peixes/isolamento & purificação , Peixes , Oligopeptídeos/isolamento & purificação , Hidrolisados de Proteína/química , Inibidores da Enzima Conversora de Angiotensina/química , Animais , Fracionamento Químico , Cromatografia de Fase Reversa , Proteínas de Peixes/química , UltrafiltraçãoRESUMO
Objective: To establish the pre-column derivatization combining HPLC to determine the contents of the amino acids of the raw and processed products of Turtle shell. Methods: The samples were prepared by the acidic hydrolysis method, derivatized by OPA and FMOC, and analyzed by C18 column with gradient elution. Results: 18 kinds of amino acids were separated within 38 min, which showed a good linear relationship( r ≥0. 9991). The average recoveries of 16 amino acids in the samples were between 90. 43% ~110. 69%,and the RSD were between 0. 76% ~ 5. 89%( n = 6). Conclusion: This method can be used to determine the contents of the amino acids in the raw and processed products of Turtle shell.
Assuntos
Tartarugas , Aminoácidos , Animais , Cromatografia Líquida de Alta PressãoRESUMO
Lizard fish (Saurida elongata) muscle protein was hydrolyzed using neutral protease to produce protein hydrolysate (LFPH), and the hydrolysis conditions were investigated using response-surface methodology. The optimum conditions for producing peptides with the highest angiotensin-I converting enzyme (ACE)-inhibitory activity were the following: enzyme-to-substrate ratio of 10,000 U/g, temperature of 48 °C, pH 7.0, and hydrolysis time of 2 h. Under these conditions, the ACE-inhibitory activity of LFPH and the degree of hydrolysis were 84% and 24%, respectively. A novel ACE-inhibitory peptide was isolated from LFPH using ultrafiltration, Sephadex G-15, and high-performance liquid chromatography. The amino acid sequence of the ACE-inhibitory peptide was identified as Ser-Pro-Arg-Cys-Arg (SPRCR), and its IC50 was 41 ± 1 µM.
Assuntos
Inibidores da Enzima Conversora de Angiotensina/isolamento & purificação , Inibidores da Enzima Conversora de Angiotensina/metabolismo , Proteínas Musculares/isolamento & purificação , Peptídeos/isolamento & purificação , Hidrolisados de Proteína/isolamento & purificação , Sequência de Aminoácidos , Inibidores da Enzima Conversora de Angiotensina/química , Animais , Cromatografia Líquida de Alta Pressão/métodos , Peixes/metabolismo , Concentração de Íons de Hidrogênio , Hidrólise , Proteínas Musculares/química , Proteínas Musculares/metabolismo , Peptídeo Hidrolases/química , Peptídeo Hidrolases/metabolismo , Peptídeos/química , Peptídeos/metabolismo , Hidrolisados de Proteína/química , Hidrolisados de Proteína/metabolismo , TemperaturaRESUMO
CONTEXT: Angiotensin-converting enzyme (ACE) is one of the main regulators of blood pressure through its action on the renin-angiotensin system. ACE inhibitory peptides from natural materials inhibit ACE activity and have considerable importance as antihypertensive agents. OBJECTIVE: A new chromogenic reaction method for determining hippuric acid (HA) and angiotensin I-converting enzyme (ACE) inhibitor activity was developed. MATERIALS AND METHODS: This method is based on the reaction of HA with p-dimethylaminobenzaldehyde in the presence of quinoline, acetate, and acetic anhydride. The red-orange formation product in the reaction has a stable absorbance in the visible region and it was determined at 478 nm. The assay conditions were optimized and by using an ACE concentration of 12 mU/mL in enzymatic reaction, the method was applied to monitor the IC(50) values (the concentration of inhibitor required to inhibit 50% of the ACE activity) for captopril and Saurida elongata (Synodontidae) muscle protein hydrolyzate. RESULTS: With the proposed method, IC(50) values for captopril and Saurida elongata muscle protein hydrolyzate were determined as 0.0123 µM and 0.1648 mg/mL, respectively. Those results correspond to the IC(50) values of 0.0109 µM and 0.1820 mg/mL obtained by high-performance liquid chromatography (HPLC) method. DISCUSSION AND CONCLUSION: The proposed method is rapid, accurate, reproducible and convenient, and suitable for screening ACE inhibitor peptides from food materials while it does not require HA extraction from the components of the ACE activity assay reaction.
Assuntos
Inibidores da Enzima Conversora de Angiotensina/farmacologia , Colorimetria/métodos , Inibidores da Enzima Conversora de Angiotensina/administração & dosagem , Inibidores da Enzima Conversora de Angiotensina/química , Animais , Captopril/administração & dosagem , Captopril/farmacologia , Cromatografia Líquida de Alta Pressão , Peixes , Hipuratos/química , Concentração Inibidora 50 , Hidrolisados de Proteína/administração & dosagem , Hidrolisados de Proteína/farmacologia , Reprodutibilidade dos TestesRESUMO
The interaction between angiotensin I-converting enzyme (ACE) and the inhibitory peptide KNFL from Wakame was explored using isothermal titration calorimetry, multiple spectroscopic techniques and molecular dynamics simulations, and an inhibition model was established based on free energy binding theory. The experiments revealed that the binding of KNFL to ACE was a spontaneous exothermic process driven by enthalpy and entropy and occurred via multiple binding sites to form stable complexes. The complexes may be formed through multiple steps of inducing fit and conformational selection. The peptide KNFL had a fluorescence quenching effect on ACE and its addition not only affected the microenvironment around the ACE Trp and Tyr residues, but also increased the diameter and altered the conformation of ACE. This study should prove useful for improving our understanding of the mechanism of ACE inhibitory peptides.
Assuntos
Peptidil Dipeptidase A , Undaria , Inibidores da Enzima Conversora de Angiotensina/química , Cinética , Simulação de Acoplamento Molecular , Peptídeos/química , Peptidil Dipeptidase A/metabolismo , Undaria/metabolismoRESUMO
To remove the bisphenol AF (BPAF) from aqueous solution, two different types of lignin-based aromatic porous polymers (LAPP-1 and LAPP-2) were fabricated via one-pot crosslinking of lignin with 1,4-dichloroxylene and 4,4'-bis(chloromethyl)-1,1'-biphenyl, respectively. The successful synthesis of LAPPs was confirmed by FTIR and XPS, SEM, TEM and N2 adsorption-desorption analysis. Then, batch adsorption experiments were conducted to investigate adsorption properties toward BPAF. Based on the results, the adsorption processes were in accordance with the pseudo-second-order kinetic model and the Freundlich isotherm model, and the thermodynamic studies showed that the adsorption was a spontaneous and exothermic process. It is remarkable that LAPPs exhibited good adsorption performance in wide ranges of pH and ionic strength as well as in recycling process. Notably, compared to LAPP-1, LAPP-2 exhibited higher adsorption capacity for BPAF, which can be ascribed to its higher porosity and content of aromatic ring. Moreover, the comprehensive analysis of experimental and theoretical results indicated that the π-π interactions and pore adsorption may jointly drive the uptake process of BPAF. Considering the simple fabrication method employed and excellent BPAF adsorption performance, LAPPs provided new insights into the development of advanced lignin-based adsorbents for removal of BPAF from water.
Assuntos
Compostos Benzidrílicos/isolamento & purificação , Lignina/síntese química , Fenóis/isolamento & purificação , Purificação da Água/métodos , Adsorção , Compostos Benzidrílicos/química , Concentração de Íons de Hidrogênio , Cinética , Fenóis/química , Polímeros/síntese química , Porosidade , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Termodinâmica , Água/química , Poluentes Químicos da Água/químicaRESUMO
Papain was immobilized onto Ti3C2 MXene nanosheets by physical adsorption and physical adsorption combined with covalent crosslinking with glutaraldehyde. Ti3C2 MXene nanosheets were prepared by hydrofluoric acid etching method. The resulting products were well characterized by SEM, BET, XRD, FTIR, XPS. The optimized immobilization conditions are pH 6.5, immobilization time of 20 h, immobilization temperature of 10â, and 10 mL 2 mg mL-1 papain, the amount of papain immobilized was 156 mg g-1, the activity of the immobilized papain determined was 1701 Uâg-1. The immobilized papain exhibited enhanced pH and temperature endurances, immobilized papain also showed improved storage stability (39.25 % and 65.57 % after 20 days of storage at 4 °C). papain reusability was significantly improved after immobilization and it retained more than 50 % of its initial activity after 5 repeated cycles. Interestingly, the results of immobilized enzymes demonstrated that the immobilization of enzymes on Ti3C2 MXene is feasible. Such approach could be transferred to other support systems for anchoring enzyme.
Assuntos
Papaína , Titânio , Estabilidade Enzimática , Enzimas Imobilizadas/metabolismo , Glutaral , Concentração de Íons de Hidrogênio , TemperaturaRESUMO
Purification of small bioactive peptides from complex biological samples is a difficult task due to the interference of concentrated large biomolecules. In this study, a magnetic immobilized metal affinity chromatography matrix modified by poly (ethylene glycol) methyl ether (IMACM@mPEG) was prepared and applied for the rapid purification of angiotensin I-converting enzyme (ACE) inhibitory peptides from casein hydrolysate. The proposed IMACM@mPEG considerably reduced the non-specific adsorption of large proteins and exhibited improved purification efficiency towards ACE inhibitory peptides. A novel peptide with moderate ACE inhibitory activity (IC50 value of 274 ± 5 µM) was identified as LLYQEPVLGPVR. Lineweaver-Burk plot confirmed the non-competitive inhibition pattern of LLYQEPVLGPVR. The purified peptide was digested after simulated gastrointestinal digestion and produced shorter peptides which contributed to enhanced ACE inhibitory activity. These results indicated that the IMACM@mPEG is an effective method for the prepurification of ACE inhibitory peptide and the purified peptide LLYQEPVLGPVR may have potential as nutraceutical ingredient in functional foods for hypertension treatments.
Assuntos
Inibidores da Enzima Conversora de Angiotensina/isolamento & purificação , Caseínas/química , Cromatografia de Afinidade/métodos , Éteres/química , Peptídeos/isolamento & purificação , Polietilenoglicóis/química , Adsorção , Sequência de Aminoácidos , Inibidores da Enzima Conversora de Angiotensina/análise , Inibidores da Enzima Conversora de Angiotensina/metabolismo , Cobre/química , Óxido Ferroso-Férrico/química , Microesferas , Peptídeos/análise , Peptídeos/metabolismo , Hidrolisados de Proteína , Dióxido de Silício/metabolismo , Propriedades de SuperfícieRESUMO
In the past years, considerable efforts have been devoted to the deliberate synthesis of nanosulfur in various hosts with sophisticated structures to improve the performance of lithium-sulfur batteries (LSBs) and reveal the structure-property relationship. It is taken for granted that these elaborate sulfur nanostructures are well maintained in the ultimate electrode after the traditional mixing and coating method. Herein, we, for the first time, reveal the unexpected sulfur structure deterioration in nanosulfur/graphene composites during the electrode preparation using the traditional method because of the long-term neglected dissolution-recrystallization effect of sulfur in solvents. Consequently, compared with binder-free three-dimensional graphene/sulfur electrodes, the milled graphene/sulfur electrodes exhibit much worse electrochemical performance. On the basis of this, we further propose a facile and universal graphene oxide-assisted assembly method to avoid the dissolution-recrystallization of sulfur, by which binder-free three-dimensional ethylenediamine-functionalized graphene/sulfur (3DEFGS) electrodes have been successfully prepared. The 3DEFGS electrodes with a high areal sulfur loading of â¼6 mg cm-2 exhibit an ultrahigh initial capacity of 1394 mA h g-1 at 0.1 C, an excellent rate performance with a capacity of 796 mA h g-1 at 4 C, and superior long-term cycling stability (885 mA h g-1 after 500 cycles at 1 C), which are among the best performances achieved by all reported LSB cathodes with high areal sulfur loadings.
RESUMO
Carapax Trionycis (the shell of the turtle Pelodiscus sinensis) was hydrolyzed by six different commercial proteases. The hydrolysate prepared from papain showed stronger inhibitory activity against angiotensin I-converting enzyme (ACE) than other extracts. Two noncompetitive ACE inhibitory peptides were purified successively by ultrafiltration, gel filtration chromatography, ion exchange column chromatography, and high-performance liquid chromatography (HPLC). The amino acid sequences of them were identified as KRER and LHMFK, with IC50 values of 324.1 and 75.6 µM, respectively, confirming that Carapax Trionycis is a potential source of active peptides possessing ACE inhibitory activities. Besides, both enzyme kinetics and isothermal titration calorimetry (ITC) assay showed that LHMFK could form more stable complex with ACE than KRER, which is in accordance with the better inhibitory activity of LHMFK.
Assuntos
Inibidores da Enzima Conversora de Angiotensina/química , Inibidores da Enzima Conversora de Angiotensina/farmacologia , Peptídeos/farmacologia , Tartarugas , Sequência de Aminoácidos , Inibidores da Enzima Conversora de Angiotensina/metabolismo , Animais , Cromatografia em Gel , Cromatografia Líquida de Alta Pressão , Avaliação Pré-Clínica de Medicamentos/métodos , Hidrólise , Concentração Inibidora 50 , Peptídeo Hidrolases/metabolismo , Peptídeos/química , Peptídeos/isolamento & purificação , Hidrolisados de Proteína/química , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , Relação Estrutura-AtividadeRESUMO
Angiotensin-converting enzyme (ACE) inhibitory peptides derived from food protein exhibited antihypertensive effects by inhibiting ACE activity. In this work, the interaction between ACE inhibitory peptide GMKCAF (GF-6) and ACE was studied by isothermal titration calorimetry (ITC), molecular docking, ultraviolet absorption spectroscopy, fluorescence spectroscopy, and circular dichroism spectroscopy. Experimental results revealed that the binding of GF-6 to ACE was a spontaneous exothermic process driven by both enthalpy and entropy. The interaction occurred via a static quenching mechanism and involved the alteration of the conformation of ACE. In addition, ITC and molecular docking results indicated binding of GF-6 to ACE via multiple binding sites on the protein surface. This study could be deemed helpful for the better understanding of the inhibitory mechanism of ACE inhibitory peptides.
Assuntos
Inibidores da Enzima Conversora de Angiotensina/química , Proteínas de Peixes/química , Peptídeos/metabolismo , Peptidil Dipeptidase A/química , Inibidores da Enzima Conversora de Angiotensina/metabolismo , Animais , Anti-Hipertensivos/química , Anti-Hipertensivos/metabolismo , Sítios de Ligação , Proteínas de Peixes/metabolismo , Peixes , Cinética , Simulação de Acoplamento Molecular , Peptídeos/química , Peptidil Dipeptidase A/metabolismo , Espectrometria de Fluorescência , Suínos , TermodinâmicaRESUMO
Cell density and morphology changes were tested to examine the effects of salts including NaHCO3 , NaCl, KHCO3 , and KCl at 160 mM on protozoa. It was demonstrated that ionic stress rather than osmotic stress led to protozoa cell death and NaHCO3 was shown to be the most effective inhibitor. Deformation of cells and cell shrinkage were observed when protozoan cells were exposed to polyethylene glycol (PEG) or any of the salts. However, while PEG treated cells could fully recover in both number and size, only a small portion of the salt-treated cells survive and cell size was 36-58% smaller than the regular. The disappearance of salt-treated protozoa cells was hypothetically attributed to disruption of the cytoplasmic membrane of these cells. It is further hypothesized that the PEG-treated protozoan cells carried out regulatory volume increase (RVI) after the osmotic shock but the RVI of salt-treated protozoa was hurdled to varied extents. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1418-1424, 2017.