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1.
Nat Commun ; 15(1): 7891, 2024 Sep 10.
Article de Anglais | MEDLINE | ID: mdl-39256395

RÉSUMÉ

The identification effector targets and characterization of their functions are crucial for understanding pathogen infection mechanisms and components of plant immunity. Here, we identify the effector UgsL, a ustilaginoidin synthetase with a key role in regulating virulence of the rice false smut fungus Ustilaginoidea virens. Heterologous expression of UgsL in rice (Oryza sativa) enhances plant susceptibility to multiple pathogens, and host-induced gene silencing of UgsL enhances plant resistance to U. virens, indicating that UgsL inhibits rice immunity. UgsL interacts with STRUBBELIG RECEPTOR KINASE 3 (OsSRF3). Genome editing and overexpression of OsSRF3 demonstrate that OsSRF3 plays a pivotal role in the resistance of rice to multiple pathogens. Remarkably, overexpressing OsSRF3 enhances resistance without adversely affecting plant growth or yield. We show that BRASSINOSTEROID RECEPTOR-ASSOCIATED KINASE 1 (OsBAK1) interacts with and phosphorylates OsSRF3 to activate pathogen-triggered immunity, inducing the mitogen-activated protein kinase cascade, a reactive oxygen species burst, callose deposition, and expression of defense-related genes. UgsL interferes with the phosphorylation of OsSRF3 by OsBAK1. Furthermore, UgsL mediates OsSRF3 degradation by facilitating its association with the ubiquitin-26S proteasome. Our results reveal that OsSRF3 positively regulates immunity in rice and that UgsL mediates its degradation, thereby inhibiting the activation of OsBAK1-OsSRF3-mediated immune pathways.


Sujet(s)
Régulation de l'expression des gènes végétaux , Oryza , Maladies des plantes , Immunité des plantes , Protéines végétales , Résistance à la maladie/génétique , Protéines fongiques/métabolisme , Protéines fongiques/génétique , Interactions hôte-pathogène , Hypocreales/pathogénicité , Hypocreales/génétique , Oryza/microbiologie , Oryza/immunologie , Oryza/génétique , Phosphorylation , Maladies des plantes/microbiologie , Maladies des plantes/immunologie , Protéines végétales/métabolisme , Protéines végétales/génétique , Végétaux génétiquement modifiés , Protein kinases/métabolisme , Protein kinases/génétique , Protein-Serine-Threonine Kinases/métabolisme , Protein-Serine-Threonine Kinases/génétique , Espèces réactives de l'oxygène/métabolisme
2.
BMC Psychiatry ; 24(1): 597, 2024 Sep 04.
Article de Anglais | MEDLINE | ID: mdl-39232691

RÉSUMÉ

Depersonalization/derealization disorder (DPD) is a prevalent yet inadequately understood clinical condition characterized by a recurrent or persistent sense of unreality. This study aims to provide insight into DPD through descriptive and comparative analyses involving a large group of Chinese participants. The socio-demographic details (age, gender proportion, education, occupational status, marital status), depersonalized and dissociative symptom characteristics (symptomatic factors or subscales of the Cambridge Depersonalization Scale and the Dissociative Experiences Scale), development trajectory (age of onset, potential precipitating factors, course characteristics), treatment history (duration of delayed healthcare attendance, duration of delayed diagnosis, previous diagnoses), and adverse childhood experiences of the DPD patients are presented. Comparisons of anxiety and depressive symptoms, alongside psychosocial functioning, between DPD participants and those diagnosed with generalized anxiety disorder, bipolar disorders, and major depressive disorder were conducted. The analysis highlights a higher male preponderance and early onset of DPD, symptomatology marked by derealization, notable impairment in psychosocial functioning, and prolonged periods of delayed healthcare attendance and diagnosis associated with symptom severity. Furthermore, noteworthy relationships between adverse childhood experiences and symptom levels were identified. The findings substantiate the view that DPD is a serious but neglected mental disorder, urging initiatives to improve the current condition of DPD patients.


Sujet(s)
Dépersonnalisation , Adolescent , Adulte , Femelle , Humains , Mâle , Adulte d'âge moyen , Jeune adulte , Expériences défavorables de l'enfance/psychologie , Âge de début , Troubles anxieux/épidémiologie , Troubles anxieux/psychologie , Trouble bipolaire/psychologie , Trouble bipolaire/épidémiologie , Chine/épidémiologie , Retard de diagnostic , Dépersonnalisation/psychologie , Trouble dépressif majeur/épidémiologie , Trouble dépressif majeur/psychologie , Troubles dissociatifs/psychologie , Troubles dissociatifs/épidémiologie , Peuples d'Asie de l'Est/psychologie , Facteurs sexuels
4.
Cancer Commun (Lond) ; 2024 Jul 25.
Article de Anglais | MEDLINE | ID: mdl-39051512

RÉSUMÉ

Dendritic cells (DCs) comprise diverse cell populations that play critical roles in antigen presentation and triggering immune responses in the body. However, several factors impair the immune function of DCs and may promote immune evasion in cancer. Understanding the mechanism of DC dysfunction and the diverse functions of heterogeneous DCs in the tumor microenvironment (TME) is critical for designing effective strategies for cancer immunotherapy. Clinical applications targeting DCs summarized in this report aim to improve immune infiltration and enhance the biological function of DCs to modulate the TME to prevent cancer cells from evading the immune system. Herein, factors in the TME that induce DC dysfunction, such as cytokines, hypoxic environment, tumor exosomes and metabolites, and co-inhibitory molecules, have been described. Furthermore, several key signaling pathways involved in DC dysfunction and signal-relevant drugs evaluated in clinical trials were identified. Finally, this review provides an overview of current clinical immunotherapies targeting DCs, especially therapies with proven clinical outcomes, and explores future developments in DC immunotherapies.

5.
Ultrasonics ; 141: 107342, 2024 Jul.
Article de Anglais | MEDLINE | ID: mdl-38754150

RÉSUMÉ

In this study, the microstructural evolution and mechanical properties of Ti6Al4V titanium alloy welded joints subjected to ultrasonic assisted laser welding were scrutinized, while numerical simulations were employed to explicate the grain refinement mechanism. The simulations indicate that the ultrasonic vibration significantly improves the overall fluidity and temperature of the molten pool. Under the identical condition of laser power and welding speed (1500 W, 1.3 m/min), the presence of 0.2A ultrasonic current yields a more uniform refinement of columnar grains, along with a denser arrangement of acicular martensite. The refinement mechanism can be attributed to the small temperature gradient, cavitation effects, and stress induced by ultrasonic vibration. Notably, the welded joint attains a peak tensile strength of 945.2 MPa under the aforementioned 0.2A condition, distinctly demonstrating the characteristics of ductile fracture. This research further reveals the underlying mechanism of grain refinement in Ti6Al4V alloy laser-welded joints induced by ultrasonic vibration, providing valuable references for optimizing process parameters and improving the quality of such welded joints.

6.
Plant Biotechnol J ; 22(1): 148-164, 2024 Jan.
Article de Anglais | MEDLINE | ID: mdl-37715970

RÉSUMÉ

Rice false smut caused by Ustilaginoidea virens is a devastating rice (Oryza sativa) disease worldwide. However, the molecular mechanisms underlying U. virens-rice interactions are largely unknown. In this study, we identified a secreted protein, Uv1809, as a key virulence factor. Heterologous expression of Uv1809 in rice enhanced susceptibility to rice false smut and bacterial blight. Host-induced gene silencing of Uv1809 in rice enhanced resistance to U. virens, suggesting that Uv1809 inhibits rice immunity and promotes infection by U. virens. Uv1809 suppresses rice immunity by targeting and enhancing rice histone deacetylase OsSRT2-mediated histone deacetylation, thereby reducing H4K5ac and H4K8ac levels and interfering with the transcriptional activation of defence genes. CRISPR-Cas9 edited ossrt2 mutants showed no adverse effects in terms of growth and yield but displayed broad-spectrum resistance to rice pathogens, revealing a potentially valuable genetic resource for breeding disease resistance. Our study provides insight into defence mechanisms against plant pathogens that inactivate plant immunity at the epigenetic level.


Sujet(s)
Hypocreales , Oryza , Oryza/génétique , Oryza/microbiologie , Histone , Amélioration des plantes , Hypocreales/génétique , Maladies des plantes/microbiologie
7.
Mol Cell Proteomics ; 22(8): 100616, 2023 08.
Article de Anglais | MEDLINE | ID: mdl-37442371

RÉSUMÉ

Lysine ß-hydroxybutyrylation (Kbhb) is an evolutionarily conserved and widespread post-translational modification that is associated with active gene transcription and cellular proliferation. However, its role in phytopathogenic fungi remains unknown. Here, we characterized Kbhb in the rice false smut fungus Ustilaginoidea virens. We identified 2204 Kbhb sites in 852 proteins, which are involved in diverse biological processes. The mitogen-activated protein kinase UvSlt2 is a Kbhb protein, and a strain harboring a point mutation at K72, the Kbhb site of this protein, had decreased UvSlt2 activity and reduced fungal virulence. Molecular dynamic simulations revealed that K72bhb increases the hydrophobic solvent-accessible surface area of UvSlt2, thereby affecting its binding to its substrates. The mutation of K298bhb in the septin UvCdc10 resulted in reduced virulence and altered the subcellular localization of this protein. Moreover, we confirmed that the NAD+-dependent histone deacetylases UvSirt2 and UvSirt5 are the major enzymes that remove Kbhb in U. virens. Collectively, our findings identify regulatory elements of the Kbhb pathway and reveal important roles for Kbhb in regulating protein localization and enzymatic activity. These findings provide insight into the regulation of virulence in phytopathogenic fungi via post-translational modifications.


Sujet(s)
Hypocreales , Oryza , Virulence , Hypocreales/génétique , Maturation post-traductionnelle des protéines , Mutation , Maladies des plantes/microbiologie
8.
Plant Commun ; 4(3): 100550, 2023 05 08.
Article de Anglais | MEDLINE | ID: mdl-36654509

RÉSUMÉ

Pathogen attack can increase plant levels of reactive oxygen species (ROS), which act as signaling molecules to activate plant defense mechanisms. Elucidating these processes is crucial for understanding redox signaling pathways in plant defense responses. Using an iodo-tandem mass tag (TMT)-based quantitative proteomics approach, we mapped 3362 oxidized cysteine sites in 2275 proteins in rice leaves. Oxidized proteins were involved in gene expression, peptide biosynthetic processes, stress responses, ROS metabolic processes, and translation pathways. Magnaporthe oryzae infection led to increased oxidative modification levels of 512 cysteine sites in 438 proteins, including many transcriptional regulators and ribosomal proteins. Ribosome profiling (Ribo-seq) analysis revealed that the oxidative modification of ribosomal proteins promoted the translational efficiency of many mRNAs involved in defense response pathways, thereby affecting rice immunity. Our results suggest that increased oxidative modification of ribosomal proteins in rice leaves promotes cytosolic translation, thus revealing a novel function of post-translational modifications. Furthermore, the oxidation-sensitive proteins identified here provide a valuable resource for research on protein redox regulation and can guide future mechanistic studies.


Sujet(s)
Magnaporthe , Oryza , Résistance à la maladie , Espèces réactives de l'oxygène/métabolisme , Oryza/métabolisme , Magnaporthe/métabolisme , Protéomique/méthodes , Cystéine/métabolisme , Protéines végétales/génétique , Protéines végétales/métabolisme , Protéines ribosomiques/génétique , Oxydoréduction , Feuilles de plante/métabolisme
9.
Mol Plant Microbe Interact ; 35(12): 1120-1123, 2022 Dec.
Article de Anglais | MEDLINE | ID: mdl-36510363

RÉSUMÉ

Rice false smut (RFS), caused by Ustilaginoidea virens, has become a major disease in recent years, and mycotoxins produced by U. virens often threaten food safety. To study fungal pathogenesis and identify potential targets for developing new fungicides, gap-free nuclear and complete mitochondrial genomes of U. virens JS60-2 were sequenced and assembled. Using the second and third generation sequencing data, we assembled a 38.02-Mb genome that consists of seven contigs with the contig N50 being 6.32-Mb. In total, 8,486 protein-coding genes were annotated in the genome, including 21 secondary metabolism gene clusters. We also assembled the complete mitochondrial genome, which is 102,498 bp, with 28% GC content. The JS60-2 genomes assembled in this study will facilitate research on U. virens and contribute to RFS control. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.


Sujet(s)
Génome mitochondrial , Hypocreales , Oryza , Oryza/microbiologie , Maladies des plantes/microbiologie , Hypocreales/génétique
10.
Plant Physiol ; 190(2): 1474-1489, 2022 09 28.
Article de Anglais | MEDLINE | ID: mdl-35861434

RÉSUMÉ

Serine protease subtilase, found widely in both eukaryotes and prokaryotes, participates in various biological processes. However, how fungal subtilase regulates plant immunity is a major concern. Here, we identified a secreted fungal subtilase, UvPr1a, from the rice false smut (RFS) fungus Ustilaginoidea virens. We characterized UvPr1a as a virulence effector localized to the plant cytoplasm that inhibits plant cell death induced by Bax. Heterologous expression of UvPr1a in rice (Oryza sativa) enhanced plant susceptibility to rice pathogens. UvPr1a interacted with the important rice protein SUPPRESSOR OF G2 ALLELE OF skp1 (OsSGT1), a positive regulator of innate immunity against multiple rice pathogens, degrading OsSGT1 in a protease activity-dependent manner. Furthermore, host-induced gene silencing of UvPr1a compromised disease resistance of rice plants. Our work reveals a previously uncharacterized fungal virulence strategy in which a fungal pathogen secretes a subtilase to interfere with rice immunity through degradation of OsSGT1, thereby promoting infection. These genetic resources provide tools for introducing RFS resistance and further our understanding of plant-pathogen interactions.


Sujet(s)
Oryza , Allèles , Interactions hôte-pathogène/génétique , Oryza/métabolisme , Maladies des plantes/génétique , Maladies des plantes/microbiologie , Protéases à sérine/génétique , Protéases à sérine/métabolisme , Protéine Bax/génétique , Protéine Bax/métabolisme
11.
New Phytol ; 235(5): 1977-1994, 2022 09.
Article de Anglais | MEDLINE | ID: mdl-35592995

RÉSUMÉ

Histone acetylation is a critical epigenetic modification that regulates plant immunity. Fungal pathogens secrete effectors that modulate host immunity and facilitate infection, but whether fungal pathogens have evolved effectors that directly target plant histone acetylation remains unknown. Here, we identified a secreted protein, UvSec117, from the rice false smut fungus, Ustilaginoidea virens, as a key effector that can target the rice histone deacetylase OsHDA701 and negatively regulates rice broad-spectrum resistance against rice pathogens. UvSec117 disrupts host immunity by recruiting OsHDA701 to the nucleus and enhancing OsHDA701-modulated deacetylation, thereby reducing histone H3K9 acetylation levels in rice plants and interfering with defense gene activation. Host-induced gene silencing of UvSec117 promotes rice resistance to U. virens, thus providing an alternative way for developing rice false smut-resistant plants. This is the first direct evidence demonstrating that a fungal effector targets a histone deacetylase to suppress plant immunity. Our data provided insight into a counter-defense mechanism in a plant pathogen that inactivates host defense responses at the epigenetic level.


Sujet(s)
Oryza , Histone deacetylases , Histone , Oryza/génétique , Oryza/microbiologie , Maladies des plantes/microbiologie , Immunité des plantes
12.
Article de Anglais | MEDLINE | ID: mdl-35432570

RÉSUMÉ

Objective: To explore the mechanism of Shaoyao Gancao decoction (SGD) in treatment of alopecia areata (AA) by network pharmacology and animal experiments. Methods: Based on the traditional Chinese medicine systems pharmacology database and analysis platform (TCMSP), the components and targets of SGD were determined. Then, the related targets of AA were retrieved from DrugBank, GeneCards, OMIM, and DisGeNET databases. The intersection of drug targets and disease targets was determined, and the key targets of the protein-protein interaction network were obtained with the String database. Gene Ontology (GO) biological process enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of potential key targets were carried out using the DAVID database using AutoDock for molecular docking verification. Finally, the key pathway was validated by animal experiments. Results: A total of 102 active components, 212 predicted targets, and 812 AA disease-related targets were obtained. Topological analysis yielded 45 key targets of SGD in the treatment of AA, including IL-6, PTGS2, TNF, VEGFA, CCL2, IL-1B, CXCL8, CASP3, MPO, and IL-10. There were 324 GO entries obtained through GO biological process enrichment analysis, and 20 pathways were obtained through KEGG pathway enrichment analysis, involving the PI3K-Akt signaling pathway, osteoclast differentiation, and Jak-STAT signaling pathway. The molecular docking results showed effective ingredients (quercetin, kaempferol, and 7-methoxy-2-methyl isoflavone) have good docking results with targets (IL-6, PTGS2, and TNF). The results of animal experiments showed that SGD can effectively upregulate the expression of PI3K and AKT proteins. Conclusion: This is the first in-depth study on the mechanism of SGD's treatment effect in AA using network pharmacology, and preliminary animal experiments verified that it is closely related to the PI3K/AKT signaling pathway. This finding may provide a new basis for SGD's clinical application in AA.

13.
J Fungi (Basel) ; 7(11)2021 Nov 10.
Article de Anglais | MEDLINE | ID: mdl-34829234

RÉSUMÉ

Rice false smut caused by Ustilaginoidea virens is a serious disease of rice (Oryza sativa), severely reducing plant mass and yields worldwide. We performed genome-wide analysis of the CCHC-type zinc-finger transcription factor family in this pathogen. We identified and functionally characterized seven UvCCHC genes in U. virens. The deletion of various UvCCHC genes affected the stress responses, vegetative growth, conidiation, and virulence of U. virens. ∆UvCCHC5 mutants infected rice spikelets normally but could not form smut balls. Sugar utilization experiments showed that the ∆UvCCHC5 mutants were defective in the utilization of glucose, sucrose, lactose, stachyose, and trehalose. Deletion of UvCCHC5 did not affect the expression of rice genes associated with grain filling, as revealed by RT-qPCR. We propose that the ∆UvCCHC5 mutants are impaired in transmembrane transport, and the resulting nutrient deficiencies prevent them from using nutrients from rice to form smut balls. RNA-seq data analysis indicated that UvCCHC4 affects the expression of genes involved in mitochondrial biogenesis, ribosomes, transporters, and ribosome biogenesis. These findings improve our understanding of the molecular mechanism underlying smut ball formation in rice by U. virens.

14.
J Integr Plant Biol ; 63(10): 1801-1814, 2021 Oct.
Article de Anglais | MEDLINE | ID: mdl-34245484

RÉSUMÉ

The post-translational modification lysine 2-hydroxyisobutyrylation (Khib ) plays an important role in gene transcription, metabolism, and enzymatic activity. Khib sites have been identified in rice (Oryza sativa). However, the Khib status of proteins in rice flowers during pathogen infection remains unclear. Here, we report a comprehensive identification of Khib -modified proteins in rice flowers, and the changes in these proteins during infection with the fungal pathogen Ustilaginoidea virens. By using a tandem mass tag-based quantitative proteomics approach, we identified 2,891 Khib sites on 964 proteins in rice flowers. Our data demonstrated that 2-hydroxyisobutyrylated proteins are involved in diverse biological processes. Khib levels were substantially reduced upon infection with U. virens. Chromatin immunoprecipitation polymerase chain reaction (PCR) and reverse transcription quantitative PCR analyses revealed that histone Khib is involved in the expression of disease-resistance genes. More importantly, most quantified sites on core histones H3 were downregulated upon U. virens infection. In addition, the histone deacetylases HDA705, HDA716, SRT1, and SRT2 are involved in the removal of Khib marks in rice. HDA705 was further confirmed to negatively regulate rice disease resistance to pathogens U. virens, Magnaporthe oryzae, and Xanthomonas oryzae pv. oryzae (Xoo). Our data suggest that U. virens could modulate Khib in rice flowers during infection.


Sujet(s)
Fleurs/microbiologie , Interactions hôte-pathogène , Hypocreales/physiologie , Oryza/microbiologie , Maturation post-traductionnelle des protéines , Résistance à la maladie , Fleurs/métabolisme , Histone deacetylases/métabolisme , Oryza/métabolisme , Cartes d'interactions protéiques , Protéome
15.
Int J Mol Sci ; 22(8)2021 Apr 15.
Article de Anglais | MEDLINE | ID: mdl-33920773

RÉSUMÉ

Rice false smut is a fungal disease distributed worldwide and caused by Ustilaginoidea virens. In this study, we identified a putative ester cyclase (named as UvEC1) as being significantly upregulated during U. virens infection. UvEC1 contained a SnoaL-like polyketide cyclase domain, but the functions of ketone cyclases such as SnoaL in plant fungal pathogens remain unclear. Deletion of UvEC1 caused defects in vegetative growth and conidiation. UvEC1 was also required for response to hyperosmotic and oxidative stresses and for maintenance of cell wall integrity. Importantly, ΔUvEC1 mutants exhibited reduced virulence. We performed a tandem mass tag (TMT)-based quantitative proteomic analysis to identify differentially accumulating proteins (DAPs) between the ΔUvEC1-1 mutant and the wild-type isolate HWD-2. Proteomics data revealed that UvEC1 has a variety of effects on metabolism, protein localization, catalytic activity, binding, toxin biosynthesis and the spliceosome. Taken together, our findings suggest that UvEC1 is critical for the development and virulence of U. virens.


Sujet(s)
Protéines fongiques/métabolisme , Hypocreales/métabolisme , Hypocreales/pathogénicité , Isomerases/métabolisme , Oryza/microbiologie , Maladies des plantes/microbiologie , Protéomique , Séquence d'acides aminés , Protéines fongiques/composition chimique , Délétion de gène , Génome fongique , Hypocreales/génétique , Hypocreales/croissance et développement , Isomerases/composition chimique , Mycotoxines/génétique , Mycotoxines/métabolisme , Protéome/métabolisme , Splicéosomes/métabolisme , Spores fongiques/métabolisme , Stress physiologique , Fractions subcellulaires/métabolisme
16.
J Int Med Res ; 48(8): 300060520939702, 2020 Aug.
Article de Anglais | MEDLINE | ID: mdl-32862752

RÉSUMÉ

OBJECTIVE: We aimed to examine the relationship between the prevalence of functional dyspepsia (FD) and lifestyle habits, to identify social factors that may contribute to psychosocial disorders. METHODS: We enrolled 759 university freshmen in this study, who were categorized into the FD group and healthy group. All participants completed the validated Self-Rating Depression Scale and Self-Rating Anxiety Scale questionnaires, to assess lifestyle and social factors among participants. RESULTS: The proportion of participants with FD was 16.86%, and 67.97% were women. Diet irregularities and sleep impairment may have an effect on FD. Tea consumption may play a role in preventing FD. Participants with FD were more likely to have mood disorders than healthy participants. Most participants with FD who had mood disorders experienced mild anxiety or depression. Participants' main sources of stress arose from daily life, development, social life, life events, and participants' daily schedule. CONCLUSION: Sex and lifestyle habits, including sleeping patterns and dietary habits, can have an impact on FD. Social stress and mood disorders also have an effect on FD. FD may be prevented by adjusting lifestyle habits and psychological counseling.


Sujet(s)
Dyspepsie , Anxiété/épidémiologie , Dyspepsie/épidémiologie , Femelle , Humains , Mode de vie , Mâle , Facteurs sociaux , Enquêtes et questionnaires , Universités
17.
J Environ Sci (China) ; 74: 168-176, 2018 Dec.
Article de Anglais | MEDLINE | ID: mdl-30340670

RÉSUMÉ

This study investigates the removal of arsenite (As(III)) from water using dithionite activated by UV light. This work evaluated the removal kinetics of As(III) under UV light irradiation as affected by dithionite dose and light intensity, and characterized the nature of the precipitated solids using XPS and SEM-EDS. Photolysis of dithionite was observed by measuring dithionite concentration using UV absorbance at 315nm. This study also investigated the effect of UV light path length on soluble As concentrations to understand resolubilization mechanisms. Total soluble As concentrations were observed to decrease with reaction time due to reduction of arsenite to form solids having a yellow-orange color. The removal mechanism was found to be reductive precipitation that formed solids of elemental arsenic or arsenic sulfide. However, these solids were observed to resolubilize at later times after dithionite had been consumed. Resolubilization of As was prevented and additional As removal was obtained by frequent dosing of dithionite throughout the experiment. As(III) removal is attributed to photolysis of dithionite by UV light and production of reactive radicals that reduce As(III) and convert it to solid forms.


Sujet(s)
Arsénites/composition chimique , Arsénites/isolement et purification , Précipitation chimique , Dithionite/composition chimique , Rayons ultraviolets , Polluants chimiques de l'eau/composition chimique , Polluants chimiques de l'eau/isolement et purification , Oxydoréduction , Photolyse , Solutions
18.
Int J Biol Macromol ; 92: 1191-1196, 2016 Nov.
Article de Anglais | MEDLINE | ID: mdl-27498417

RÉSUMÉ

Chitosan-montmorillonite composites can provide hydrophobicity and amino groups to enhance the performances of montmorillonite in wastewater treatment. In this paper, low molar mass chitosan (LC) and medium molar mass chitosan (MC) were selected to intercalate a sodium montmorillonite (Mt). The adsorption isotherm of LC and MC on the Mt and the pH dependency were measured. Thermo X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the chitosan-Mt composites. Results showed that with hydrochloric acid as the solvent of chitosans, increasing pH from 3 to 5.5 enhanced the adsorption of both LC and MC on the Mt, and when the equilibrium concentration of chitosans approached 300mg/L at pH 5.5, the amount of adsorbed chitosan reached the highest level of 0.203mg/mg for LC and 0.190mg/mg for MC, respectively. When the Mt was saturated with the chitosan, the amino groups on the chitosan were bonded with the Mt through electrostatic interaction and there was monolayer of the chitosan in the interlayer space of Mt, which were confirmed by FTIR spectra and XRD patterns, respectively.


Sujet(s)
Bentonite/composition chimique , Chitosane/composition chimique , Adsorption , Concentration en ions d'hydrogène , Interactions hydrophobes et hydrophiles , Cinétique , Électricité statique , Thermodynamique , Purification de l'eau
19.
Water Res ; 53: 310-21, 2014 Apr 15.
Article de Anglais | MEDLINE | ID: mdl-24530550

RÉSUMÉ

This study investigated removal of Hg(II) from water using FeS(s) with batch and continuous contact filtration systems. For the batch system, kinetic experiments showed that removal of Hg(II) by FeS(s) was rapid at lower concentration (500 µM), but at higher concentration (1000 and 1250 µM), more time was required to achieve greater than 99% removal. The concentration of iron released to the solution remained relatively low, typically below 3 µM. This would theoretically present less than 1% of the Hg(II) removed. Thus, a simple exchange of Hg(II) for Fe(II) in the solid (FeS(s)) does not explain the results, but if the Fe(II) released could react to form another solids, low concentrations of Fe do not preclude a mechanism in which Hg(II) reacts to form HgS and release Fe(II). A continuous contact dead-end ultrafiltration (DE/UF) system was developed to treat water containing Hg(II) by applying a FeS(s) suspension with stirred or non-stirred modes. A major reason for applying stirring to the system was to investigate the role of "shear" flow in rejection of Hg(II)-contacted FeS(s) by a UF membrane and the stability of Hg on the FeS(s). The Hg(II)-contacted FeS(s) was completely rejected by the DE/UF system and mercury was strongly retained on the FeS(s) particles. Almost no release of Hg(II) (≈0 mM) from the FeS(s) solids was observed when they were contacted with 0.1M-thiosulfate, regardless of whether the system was operated in stirred or non-stirred mode. However, rapid oxidation of FeS(s) was observed in the stirred system but not in the non-stirred system. Determining the mechanism of oxidation requires further study, but it is important because oxidation reduces the ability of the solids to remove additional Hg(II).


Sujet(s)
Composés du fer II/composition chimique , Mercure/composition chimique , Ultrafiltration , Polluants chimiques de l'eau/composition chimique , Purification de l'eau/méthodes , Adsorption , Cinétique , Oxydoréduction
20.
Article de Anglais | MEDLINE | ID: mdl-24521418

RÉSUMÉ

Perchlorate can be destroyed by Advanced Reduction Processes (ARPs) that combine chemical reductants (e.g., sulfite) with activating methods (e.g., UV light) in order to produce highly reactive reducing free radicals that are capable of rapid and effective perchlorate reduction. However, natural organic matter (NOM) exists widely in the environment and has the potential to influence perchlorate reduction by ARPs that use UV light as the activating method. Batch experiments were conducted to obtain data on the impacts of NOM and wavelength of light on destruction of perchlorate by the ARPs that use sulfite activated by UV light produced by low-pressure mercury lamps (UV-L) or by KrCl excimer lamps (UV-KrCl). The results indicate that NOM strongly inhibits perchlorate removal by both ARP, because it competes with sulfite for UV light. Even though the absorbance of sulfite is much higher at 222 nm than that at 254 nm, the results indicate that a smaller amount of perchlorate was removed with the UV-KrCl lamp (222 nm) than with the UV-L lamp (254 nm). The results of this study will help to develop the proper way to apply the ARPs as practical water treatment processes.


Sujet(s)
Substances humiques/analyse , Perchlorates/composition chimique , Rayons ultraviolets , Polluants chimiques de l'eau/composition chimique , Purification de l'eau/méthodes , Chromatographie d'échange d'ions , Oxydoréduction , Perchlorates/analyse , Photochimie/méthodes , Spectrophotométrie UV , Polluants chimiques de l'eau/analyse
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