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1.
Front Public Health ; 12: 1425338, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38873324

RESUMO

Background: This study aims to explore the correlation between urban green space coverage and resident health, and to analyze its underlying mechanisms. Methods: Using panel data from 30 provinces in China from 2006 to 2022, which mainly includes urban green space coverage, general health of the population, air quality, and social connectivity. This research constructed a fixed effects model to perform baseline regression analysis. A series of robustness tests, including variable substitution, controlling for geographical differences, regional robustness tests, and shortening the time span of the study, further verified the robustness of the results. Additionally, mechanism tests were conducted to examine the positive impacts of urban green spaces on resident health by improving air quality and enhancing social connectivity. Results: The findings indicate a significant positive correlation between urban green space coverage and resident health levels. That is, the greater the area covered with urban green space, the healthier the residents of the area will be. Robustness tests support the reliability of this finding, while mechanism analysis reveals that urban green spaces have a positive impact on the health of the population by improving air quality and increasing social connectivity. Discussion: This study underscores the importance of urban green space planning in improving resident health and quality of life, providing urban planners with scientific evidence to optimize urban green systems for broader health objectives.


Assuntos
Planejamento Ambiental , China , Humanos , Poluição do Ar/estatística & dados numéricos , Parques Recreativos/estatística & dados numéricos , Nível de Saúde , Qualidade de Vida , Planejamento de Cidades
2.
Diabetes Metab Syndr Obes ; 17: 575-584, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38343582

RESUMO

Background: Type 2 diabetes (T2DM) combined nonalcoholic fatty liver disease (NAFLD) are characterized by metabolic disruptions. Liraglutide has been proved to be effective in T2DM. If LRG could regulate NAFLD combined T2DM has not been reported. Methods: Intraperitoneal injection of 1% streptozotocin (STZ) plus high-sugar and high-fat diet was used to induce NAFLD combined T2DM animal model. Palmitic acid (200 µmol/L) and glucose (25 mmol/L) incubation were used to induce cell model. The cell apoptosis, mRNA and protein expression were measured through flow cytometry, PCR, and Western blotting, respectively. Results: Liraglutide significantly improved the liver injury of NAFLD combined T2DM rats, but Com-C reversed the effect of liraglutide. The decreased AMPK/mTOR signaling pathway in the NAFLD combined T2DM animals was greatly activated by liraglutide. Com-C reversed the protection effects of liraglutide on palmitic acid+glucose induced cell damage. Conclusion: Liraglutide could greatly alleviate the damage caused by NAFLD+T2DM and palmitic acid+glucose. The protection effects of liraglutide were greatly inhibited by suppressing AMPK/mTOR signaling pathway. This research might provide a novel therapeutic strategy for the prevention and treatment of NAFLD combined T2DM disease.

3.
Int J Biol Macromol ; 254(Pt 2): 127720, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-37913882

RESUMO

Bacterial infection of wounds remains one of the major clinical challenges, calling for the urgent development of novel multifunctional biological dressings. In this study, we developed a chitosan-based supramolecular aerogel NADES/PVA/CS, constructed by hydrogen bonding between chitosan, a natural deep eutectic solvents and polyvinyl alcohol, as a novel wound dressing against bacterial infections. The effect of polyvinyl alcohol content and its incorporation within chitosan-based supramolecular aerogels were investigated. The results of antibacterial test and MTT assay showed that it has obvious inhibitory effect on Staphylococcus aureus and Escherichia coli, showing excellent biocompatibility and effectively promotes wound healing. The microstructure of chitosan-based supramolecular aerogel showed that by adjusting the addition amount of polyvinyl alcohol, it could exhibit a perfect skeleton-type 3D network structure, which also made it possess smaller density and larger porosity and exhibit excellent water absorption property, contributing to the wetting of wound surface. More importantly, chitosan-based supramolecular aerogel is an environment-friendly biomaterial, which has been verified by degradability experiment. In a word, these unique advantages provide a broad prospect for the medical application of chitosan-based supramolecular aerogel NADES/PVA/CS, and provide a new strategy for the construction of green polysaccharide medical materials.


Assuntos
Quitosana , Quitosana/química , Solventes Eutéticos Profundos , Álcool de Polivinil/química , Antibacterianos/farmacologia , Antibacterianos/química , Escherichia coli , Bandagens
4.
Int J Biol Macromol ; 255: 127698, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-37949277

RESUMO

A large number of hydrogen bonds is the main reason for hindering the dissolution and reaction of chitin, and a mild and green deacetylation method to prepare chitosan for a wider range of applications is urgent. As a non-toxic and degradable green solvent, the deep eutectic solvent can effectively interfere with the hydrogen bond network of chitin, making chitin more susceptible to other solvents. Therefore, a NADES system consisting of betaine and glycerol was proposed for application in the deacetylation reaction of chitin to facilitate further attack of N-acetyl groups by low concentrations of NaOH. After optimizing the reaction conditions, chitosan with 83.77 % deacetylation was prepared, requiring only a concentration of 25 wt% NaOH. The analysis of the product chitosan showed that NADES could not only effectively improve the degree of deacetylation, but also reduce the degree of damage to the molecular weight by alkali. In addition, the potential mechanisms involved in the deacetylation process by NADES were explored. The nature of the reaction was verified by FT-IR, XRD and theoretical calculations as the process of opening intra/intermolecular hydrogen bonds of chitin by NADES. More importantly, experimental and in-depth theoretical studies provide a reference for the green preparation of chitosan.


Assuntos
Quitina , Quitosana , Quitina/química , Solventes/química , Quitosana/química , Solventes Eutéticos Profundos , Hidróxido de Sódio , Espectroscopia de Infravermelho com Transformada de Fourier
5.
Cell Death Discov ; 9(1): 363, 2023 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-37777514

RESUMO

Obese people with acute pancreatitis (AP) have an increased risk of developing severe acute pancreatitis (SAP), which prolongs the length of hospital stay and increases mortality. Thus, elucidation of the mechanisms through which SAP occurs in obese individuals will provide clues for possible treatment targets. Differences in early events in obese or lean patients with AP have not been conclusively reported. We selected C57BL/6 mice as lean mice models, ob/ob mice or diet induced obese (DIO) mice as obese mice models and then induced experimental AP in mice via injections of caerulein. There were suppressed p-AMPK expressions in the pancreas of obese mice, compared with same-age lean C57BL/6 mice, which were further reduced in AP mice models. Obese AP mice were treated using AICAR, a direct AMPK agonist, which prevented pancreatic damage and cell death, suppressed pancreatic enzyme levels in serum, reduced the areas of fat saponification in the peritoneal cavity, prevented injury in other organs and decreased mice mortality rate. Further assays showed that AICAR activates p-AMPK to stabilize pro-caspase-8. Pro-caspase-8 enhances RIPK3 degradation, inhibits pancreatic acinar cell necroptosis, and downregulates the release of pancreatic enzymes. Thus, activation of AMPK by AICAR alleviates pancreatic acinar cell necroptosis and converts SAP to mild acute pancreatitis in obese mice.

6.
Langmuir ; 39(30): 10565-10575, 2023 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-37474454

RESUMO

The difficulty of short-process bonded Nd-Fe-B magnet waste recycling lies in the effective removal of the cured polymer matrix while protecting the magnetic powder. In this study, the polymer matrix in bonded Nd-Fe-B magnet waste was destroyed using sodium hydroxide ethanol solution, and the effect of the recycling process on the magnetic powders was studied. The nonmagnetic polymer matrix was removed, while the magnetic phase was not destroyed. The carbon and oxygen contents of the recycled magnetic powders decreased by 92.96 and 89.30%, respectively, while the MS (saturation magnetization), Mr (remanence), and Hcj (coercivity) values of the recycled magnetic powders were 99.8, 98.5, and 95.9% of the original magnetic powders, respectively. The curing and decomposition processes of the polymer matrix were also analyzed. During the curing process, dicyandiamide and bisphenol A epoxy resin acted as bridges and skeletons, respectively, finally forming a thermosetting three-dimensional network structure. In the alkaline alcohol solution, the bridges and skeletons were destroyed by the free hydroxyl groups and free hydrogen radicals in ethanol, and small molecular products were dissolved in the solution.

7.
Adv Sci (Weinh) ; 10(16): e2301312, 2023 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-37069783

RESUMO

The development of low-cost RE-Fe-B sintered magnets with large La/Ce content is of great significance for the balanced utilization of rare earth (RE) resources, but it is limited by reduced magnetic properties. In this work, the coercivity (Hcj ), remanence (Br ), maximum energy product [(BH)max ], and temperature stability are simultaneously enhanced for magnets with LaCe accounting for 40 wt% of the total RE. The synergistic regulation of the REFe2 phase, Ce-valence, and grain boundaries (GBs) in RE-Fe-B sintered magnets is realized for the first time by introducing appropriate La elements. The La elements inhibit the generation of the REFe2 phase and tend to stay in the triple junctions, promoting the segregation of the RE/Cu/Ga elements and contributing to the formation of Ce/Nd/Cu/Ga-rich continuous thicker lamellar GBs, and as a result, weakening the detrimental effect on HA caused by La element substitution and enhancing Hcj . In addition, partial La atoms entering the RE2 Fe14 B phase are beneficial for improving the Br and temperature stability of the magnets and promoting the Ce3+ ion ratio, which also provides additional benefit for Br . The findings provide an effective and feasible way to co-enhance the remanence and coercivity of RE-Fe-B sintered magnets with high Ce content.

8.
iScience ; 26(4): 106472, 2023 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-37096040

RESUMO

The impact of ship emissions on the environment cannot be ignored and should be controlled. The possibility of applying seawater electrolysis technology and a novel amide absorbent (BAD, C12H25NO) to the simultaneous desulfurization and denitrification of ship exhaust gas is entirely confirmed by using various seawater resources. Concentrated seawater (CSW) with high salinity can effectively reduce the heat generated during electrolysis and the escape of chlorine. The initial pH of the absorbent can greatly affect the NO removal capacity of the system, and the BAD could keep the pH range suitable for NO oxidation in the system for a long time. The use of fresh seawater (FSW) to dilute the electrolysis of concentrated seawater (ECSW) to make an aqueous oxidant is a more reasonable scheme; the average removal efficiencies of SO2, NO, and NOx were 97.10%, 75.41%, and 74.28%, respectively. The synergistic effect of HCO3 -/CO3 2- and BAD was shown to further restrict NO2 escape.

9.
Int J Biol Macromol ; 236: 123768, 2023 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-36812964

RESUMO

Bacterial infection is still one of the main problems observed in the clinical process of wound healing, so the development of new multifunctional biocompatible materials is an urgent clinical need. A kind of supramolecular biofilm crosslinked by hydrogen bond between natural deep eutectic solvent and chitosan was studied and successfully prepared to reduce bacterial infection. Its killing rates of Staphylococcus aureus and Escherichia coli can reach 98.86 % ± 1.90 % and 99.69 % ± 0.53 %, and it can be degraded in both soil and water, showing excellent biocompatibility and biodegradability. In addition, the supramolecular biofilm material also has the UV barrier property, which can effectively avoid the secondary injury of UV to the wound. Interestingly, the cross-linking effect of hydrogen bond makes the biofilm have a more compact structure and rough surface, and gives the biofilm strong tensile properties. Overall, owing to these unique advantages, NADES-CS supramolecular biofilm has great potential for medical applications, laying the foundation for the realization of sustainable polysaccharide materials.


Assuntos
Quitosana , Quitosana/farmacologia , Quitosana/química , Solventes Eutéticos Profundos , Materiais Biocompatíveis/química , Solventes/química , Bandagens , Biofilmes , Escherichia coli , Antibacterianos/farmacologia , Antibacterianos/química
10.
Mol Cell Biochem ; 478(5): 1109-1116, 2023 May.
Artigo em Inglês | MEDLINE | ID: mdl-36219352

RESUMO

Aging results in progressive decline of renal function as well as histological alterations including glomerulosclerosis and interstitial fibrosis. The objective of current study was to test the benefits of moderate swimming exercise in aged rats on renal function and structure and investigate its molecular mechanisms. Aged rats of 21-months old were given moderate swimming exercise for 12 weeks. Swimming exercise in aged rats led to reduced plasma levels of creatinine and blood urea nitrogen. Periodic acid-Schiff staining results revealed reduced renal injury scores in aged rats after swimming exercise. Swimming exercise in aged rats mitigated renal fibrosis and downregulated the mRNA expression of Acta2, Fn, Col1a, Col4a, and Tgfb1 in kidneys. Swimming exercise in aged rats attenuated lipid accumulation and reduced levels of triglyceride in kidneys. Swimming exercise in aged rats abated oxidative stress, evidenced by reduced MDA levels and increased MnSOD activities in kidneys. Swimming exercise in aged rats inhibited NF-κB activities and reduced renal expression of pro-inflammatory cytokines including MCP-1, IL-1ß and IL-6. Mechanistically, swimming exercise restored mRNA and protein expression of PPAR-α in kidney of aged rats. Furthermore, swimming exercise in aged rats increased expression of PPAR-α-targeting microRNAs including miR-21 and miR-34a. Collectively, swimming exercise activated PPAR-α, which partly explained the benefits of moderate swimming exercise in aging kidneys.


Assuntos
Nefropatias , MicroRNAs , Ratos , Animais , PPAR alfa/metabolismo , Natação , Nefropatias/metabolismo , Rim/metabolismo , Fibrose , MicroRNAs/metabolismo , RNA Mensageiro/metabolismo
11.
Inorg Chem ; 61(35): 13915-13923, 2022 Sep 05.
Artigo em Inglês | MEDLINE | ID: mdl-35994610

RESUMO

The fundamental safety improvement of the nuclear industry depends on two important elements: Zr(IV) and Hf(IV). However, the elementary knowledge is that separation processes of the two are difficult, so there are few existing methods to meet the requirement. Furthermore, the process is highly contaminated. The development of green and efficient ligands for the separation of Zr(IV) and Hf(IV) is beneficial to the stable development of the nuclear industry. A bisamide ligand D001 was reported for the extraction and separation of Zr(IV) and Hf(IV). D001 utilizes an anionic association mechanism to extract Zr(IV) and Hf(IV) by coordinating amide groups with metals to form complexes H2ZrCl6·2 D001 and H2HfCl6·2 D001. Using quantum chemical calculations, we illuminate the extraction mechanism of bisamide ligands and the reasons for their better coordination ability than monoamide ligands and carboxylic acid ligands. A process of bisamide extraction and separation of Zr(IV) and Hf(IV) was established, and the thermodynamic parameters of the process were investigated.

12.
Chemosphere ; 307(Pt 2): 135830, 2022 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-35944677

RESUMO

Marine engine exhaust emissions are increasingly harmful to the natural environment and human health and must be controlled. A self-synthesized amide (BAD, C12H25NO) in the laboratory shows a strong absorption capacity of nitric acid and nitrous acid, which may solve the problem that only using chlorine-based oxidant as an absorbent cannot completely absorb or retain NO2 produced by NO oxidation in previous studies. Based on Multiwfn and VMD (Visual Molecular Dynamics) program calculation, the formation mechanism of hydrogen bonds between BAD with nitric acid and nitrous acid was revealed by electrostatic potential (ESP) analysis and further confirmed by FT-IR (Fourier transform infrared spectroscopy) spectra research. Subsequently, simultaneous removal of SO2 and NOX from simulated flue gas was carried out by using NaClO/BAD as a two-phase composite absorbent, and the maximum removal efficiencies of SO2 and NOX were 98.9% and 86.6%, respectively. The recycling experiments and the engineering experiments showing that NaClO/BAD can solve the problem of absorption of NO2, and it can be a promising composite absorbent in wet desulfurization and denitrification of marine engine exhaust gas in practical applications.


Assuntos
Dióxido de Enxofre , Emissões de Veículos , Amidas , Cloro , Humanos , Ácido Nítrico/química , Dióxido de Nitrogênio/análise , Ácido Nitroso , Oxidantes , Espectroscopia de Infravermelho com Transformada de Fourier , Dióxido de Enxofre/química
13.
Int J Gen Med ; 15: 5861-5868, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35791315

RESUMO

Purpose: Helicobacter pylori is one of the most common causes of peptic ulcers, gastritis, and gastric cancers. This study investigated sex-specific differences in the prevalence of H. pylori infection and its associated factors among individuals undergoing hospital-based health examinations in southern China. Methods: This study enrolled consecutive healthy individuals who underwent regular health examinations at a hospital physical examination center between September 2020 and September 2021. Anthropometric characteristics and biochemical profiles were measured. All individuals underwent carbon-13 urea breath tests. Univariate and multivariate analyses were used to evaluate the factors associated with H. pylori infection. Results: A total of 5035 individuals (men, 59.1%; women, 40.9%) were included in the analyses. The total rate of H. pylori infection was 35.0% (men, 35.5%; women, 34.3%). In the multivariate analysis, the risk factors identified for H. pylori infections were high fasting blood glucose levels and blood pressure ≥160 mmHg in men and older age, high body mass index, and low albumin levels in women. Conclusion: These findings suggest that physicians must be aware of the metabolic factors associated with H. pylori infections in the Chinese population. Early detection of these factors and timely intervention are expected to reduce H. pylori infections and provide a theoretical basis for the primary prevention of several gastrointestinal diseases.

14.
Sci Total Environ ; 839: 156278, 2022 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-35654204

RESUMO

As a well-known hazardous material, chromium (VI) in industrial wastewater has always attracted extensive attention. Many studies have focused on the recovery of Cr (VI) which is still challenging and received considerable interest. In this study, a novel synergistic extraction system using amide as extractant and Cyanex 272 as synergistic extractant was built to recover chromium (VI) from the APV wastewater. After optimizing the process parameters of extractant concentration, initial pH, extraction temperature, extraction time, extraction phase ratio, ammonia concentration and stripping phase ratio, the final extraction and stripping efficiency reached more than 99% and 98%, respectively. The Cr2O3 product with a purity of 99.52 was prepared and the organic phase could be effectively regenerated for recycling. The extraction mechanism of chromium (VI) in the synergistic extraction system was investigated in-depth with slope method, ESI-MS analysis and FT-IR analysis. In addition, molecular electrostatic potentials analysis was used to display visually the formation process of the extract complex. This paper offered a unique approach to guide sustainable chromium (VI) recovery from hazardous wastewater with great industrial and theoretical significance.


Assuntos
Águas Residuárias , Poluentes Químicos da Água , Cromo/química , Concentração de Íons de Hidrogênio , Espectroscopia de Infravermelho com Transformada de Fourier
15.
Postgrad Med ; 134(7): 686-692, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-35653281

RESUMO

OBJECTIVE: Although a high Helicobacter pylori infection rate has been reported in dyspeptic patients, published data for the asymptomatic population are inadequate. We aimed to investigate the prevalence of H. pylori infection and the association between H. pylori infection diagnosed using the noninvasive 13C urea breath test (13C UBT) and risk factors in asymptomatic Chinese individuals. METHODS: Healthy subjects who underwent hospital health examinations in the hospital health management department from September 2020 to September 2021 were consecutively enrolled. Anthropometric and biochemical characteristics were measured, and all subjects underwent 13C UBT. Univariate and multivariate analyses were used to evaluate the factors associated with H. pylori infection. RESULTS: Of the 5007 participants included, the overall prevalence of H. pylori infection was 35.0% and was similar in men (35.5%) and women (34.2%). The prevalence of H. pylori increased by 84.8% in those aged ≥ 60 years compared with those aged < 30 years (P=0.006), and increased by 30.9% in the obese group compared with the normal weight groups (P = 0.034). Fasting blood glucose (FBG) and albumin levels showed a significant association with the prevalence of H. pylori. The prevalence of H. pylori increased by 6.9% following each 1-unit increase in FBG (P = 0.033) and decreased by 3.7% for each 1-unit increase in albumin (P = 0.012). Moreover, the results of the age stratification showed that albumin level was negatively associated with the prevalence of H. pylori in participants aged < 50 years (OR = 0.952, 95%CI: 0.921-0.985; P = 0.005). However, the prevalence of H. pylori in participants aged ≥ 50 years increased by 66.6% in the impaired glucose group compared to the normal glucose group (P = 0.003). CONCLUSION: These findings suggest that detailed and strict weight and glucose management is crucial to reduce the prevalence of H. pylori infection. Management strategies should be identified and implemented with regard to these identified factors to reduce the notable economic and healthcare burden in China.


Assuntos
Infecções por Helicobacter , Helicobacter pylori , Albuminas/análise , Glicemia , Isótopos de Carbono , China/epidemiologia , Estudos Transversais , Feminino , Infecções por Helicobacter/epidemiologia , Hospitais , Humanos , Masculino , Prevalência , Ureia
16.
J Orthop Surg Res ; 17(1): 155, 2022 Mar 09.
Artigo em Inglês | MEDLINE | ID: mdl-35264228

RESUMO

BACKGROUND: Patients with HIV have a higher prevalence of thrombocytopenia than those without HIV infection, increasing their risk of substantial perioperative blood loss (PBL) during total hip arthroplasty (THA). This study aimed to evaluate PBL risk factors in HIV-infected patients undergoing THA. METHODS: Eighteen HIV+ patients (21 hip joints) and 33 HIV- patients (36 joints) undergoing THA were enrolled in this study. PBL was calculated using the Gross equation, which comprises total blood loss (TBL), dominant blood loss (DBL), and hidden blood loss (HBL). Risk factors for post-THA PBL in both patient populations was evaluated using multivariable linear regression. RESULTS: At baseline, the HIV+ patients were younger, more likely to be male and to have elevated hemoglobin and albumin levels, and lower erythrocyte sedimentation rates than HIV- patients. There were no differences in the T-lymphocyte subsets or coagulation function between the two groups. Age and albumin level were identified as potential HBL risk factors after THA, and albumin level was associated with higher TBL. The unadjusted linear regression analysis showed that the HBL and TBL were significantly higher in HIV+ patients than in HIV- patients. However, after adjusting for other factors, no differences in DBL, HBL, or TBL were observed between HIV- and HIV+ patients. CONCLUSION: PBL was similar in both groups undergoing THA, regardless of their HIV-infection status. THA surgery is a safe and effective procedure in HIV+ patients.


Assuntos
Artroplastia de Quadril , Perda Sanguínea Cirúrgica , Soronegatividade para HIV , Soropositividade para HIV , Adolescente , Adulto , Idoso , Albuminas , Terapia Antirretroviral de Alta Atividade , Artroplastia de Quadril/efeitos adversos , Artroplastia de Quadril/métodos , Feminino , Infecções por HIV/complicações , Infecções por HIV/tratamento farmacológico , Humanos , Masculino , Pessoa de Meia-Idade , Osteonecrose , Período Perioperatório , Estudos Retrospectivos
17.
Sci Total Environ ; 799: 149437, 2021 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-34375870

RESUMO

Ship emissions problems caused by the rapid development of maritime trade can't be ignored. The NOX, SOX, CO2, PM and other toxic substances contained in the exhaust gas are extremely harmful to the environment and human health. In order to cope with the adverse effects of ship emissions and the increasingly stringent emission regulations formulated by the IMO and governments, the shipping industry needs to adopt new clean energy and high-efficiency exhaust control technologies to reduce ship emissions. This paper provides a comprehensive review, including: (1) The impact of pollutants such as NOX, SOX, CO2 and PM emitted by ships on the environment and human health; (2) New regulations about ship exhaust emissions; (3) Application of clean energy such as LNG, biodiesel, methanol, hydrogen and ammonia on ships; (4) After-treatment technology of ship exhaust gas such as SCR and EGR. And focusing on the principles, uses, characteristics, implementation obstacles and prospects of different energy and technologies, with a view to provide some help for the research on ship exhaust emissions control.


Assuntos
Poluentes Atmosféricos , Poluentes Ambientais , Poluentes Atmosféricos/análise , Humanos , Navios , Tecnologia , Emissões de Veículos/análise
18.
Sci Rep ; 11(1): 12555, 2021 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-34131203

RESUMO

This investigation reveals the mystery of the cases where magnetic like poles attract each other, and unlike poles repel one another. It is identified that for two unequally sized like poles, the pole with a higher Pc (permeance coefficient) causes a localized demagnetization (LD) to the pole with a lower Pc. If the LD is large enough, the polarity of a localized area can be reversed, resulting in an attraction between these two like poles in the LD area in a small gap. Two unusual behaviors are observed: (1) an inflection point IP appears on the force vs gap curves of all the unequally sized like poles since they have different Pc. Normally, the like poles' repelling force increases when the gap decreases, but this IP results in nonmonotonic curves, even an attractive force in a small gap; (2) for some NdFeB magnets with a low coercivity and nonlinear B-H curve in the 2nd quadrant, a repulsion can occur for these unequal sized unlike poles, after previously pairing with their like poles that left an unrecoverable LD and reversed polarity area. The relationship of the LD, the Pc ratio, and the B-H curve are also explored in this paper.

19.
Molecules ; 24(12)2019 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-31207974

RESUMO

A novel RNase R, psrnr, was cloned from the Antarctic bacterium Psychrobacter sp. ANT206 and expressed in Escherichia coli (E. coli). A bioinformatics analysis of the psrnr gene revealed that it contained an open reading frame of 2313 bp and encoded a protein (PsRNR) of 770 amino acids. Homology modeling indicated that PsRNR had reduced hydrogen bonds and salt bridges, which might be the main reason for the catalytic efficiency at low temperatures. A site directed mutation exhibited that His 667 in the active site was absolutely crucial for the enzyme catalysis. The recombinant PsRNR (rPsRNR) showed maximum activity at 30 °C and had thermal instability, suggesting that rPsRNR was a cold-adapted enzyme. Interestingly, rPsRNR displayed remarkable salt tolerance, remaining stable at 0.5-3.0 M NaCl. Furthermore, rPsRNR had a higher kcat value, contributing to its efficient catalytic activity at a low temperature. Overall, cold-adapted RNase R in this study was an excellent candidate for antimicrobial treatment.


Assuntos
Adaptação Biológica , Temperatura Baixa , Microbiologia Ambiental , Camada de Gelo/microbiologia , Psychrobacter/fisiologia , Ribonucleases/metabolismo , Tolerância ao Sal , Sequência de Aminoácidos , Regiões Antárticas , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Ativação Enzimática , Cinética , Modelos Biológicos , Conformação Molecular , Estrutura Molecular , Psychrobacter/isolamento & purificação , Ribonucleases/genética
20.
Mar Drugs ; 17(3)2019 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-30832239

RESUMO

Glutathione S-transferases are one of the most important antioxidant enzymes to protect against oxidative damage induced by reactive oxygen species. In this study, a novel gst gene, designated as hsgst, was derived from Antarctic sea ice bacterium Halomonas sp. ANT108 and expressed in Escherichia coli (E. coli) BL21. The hsgst gene was 603 bp in length and encoded a protein of 200 amino acids. Compared with the mesophilic EcGST, homology modeling indicated HsGST had some structural characteristics of cold-adapted enzymes, such as higher frequency of glycine residues, lower frequency of proline and arginine residues, and reduced electrostatic interactions, which might be in relation to the high catalytic efficiency at low temperature. The recombinant HsGST (rHsGST) was purified to apparent homogeneity with Ni-affinity chromatography and its biochemical properties were investigated. The specific activity of the purified rHsGST was 254.20 nmol/min/mg. The optimum temperature and pH of enzyme were 25 °C and 7.5, respectively. Most importantly, rHsGST retained 41.67% of its maximal activity at 0 °C. 2.0 M NaCl and 0.2% H2O2 had no effect on the enzyme activity. Moreover, rHsGST exhibited its protective effects against oxidative stresses in E. coli cells. Due to its high catalytic efficiency and oxidative resistance at low temperature, rHsGST may be a potential candidate as antioxidant in low temperature health foods.


Assuntos
Antioxidantes/química , Organismos Aquáticos/fisiologia , Proteínas de Bactérias/química , Glutationa Transferase/química , Halomonas/fisiologia , Sequência de Aminoácidos , Regiões Antárticas , Antioxidantes/isolamento & purificação , Antioxidantes/farmacologia , Proteínas de Bactérias/genética , Proteínas de Bactérias/isolamento & purificação , Temperatura Baixa/efeitos adversos , Conservação de Alimentos/métodos , Glutationa Transferase/genética , Glutationa Transferase/isolamento & purificação , Glutationa Transferase/farmacologia , Concentração de Íons de Hidrogênio , Camada de Gelo/microbiologia , Simulação de Dinâmica Molecular , Estresse Oxidativo/fisiologia , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/isolamento & purificação , Especificidade por Substrato , Termotolerância/fisiologia
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