RESUMO
Identifying the essential factors and underlying mechanisms regulating plant heat stress (HS) responses is crucial for mitigating the threat posed by HS on plant growth, development, distribution, and productivity. Here, we found that the Arabidopsis (Arabidopsis thaliana) super-killer2 (ski2) dicer-like4 (dcl4) mutant, characterized by RNA processing defects and accumulation of abundant 22-nt small interfering RNAs (siRNAs) derived from protein-coding transcripts, displayed significantly increased expression levels of HS-responsive genes and enhanced thermotolerance. These traits primarily resulted from the suppression of SMAX1-LIKE4 (SMXL4) and SMXL5, which encode two putative transcriptional regulators that belong to the SMXL protein family. While smxl4 and smxl5 single mutants were similar to wild type, the smxl4 smxl5 double mutant displayed substantially heightened seedling thermotolerance. Further investigation demonstrated that SMXL4 and SMXL5 repressed the transcription of HEAT SHOCK TRANSCRIPTION FACTOR A2 (HSFA2), encoding a master regulator of thermotolerance, independently of EAR motifs. Moreover, SMXL4 and SMXL5 interacted with HSFA1d and HSFA1e, central regulators sensing and transducing HS stimuli, and antagonistically affected their transactivation activity. In addition, HSFA2 directly bound to the SMXL4 and SMXL5 promoters, inducing their expression during recovery from HS. Collectively, our findings elucidate the role of the SMXL4/SMXL5-HSFA2 regulatory module in orchestrating plant thermotolerance under HS.
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Although the role of ethylene in tomato (Solanum lycopersicum) fruit ripening has been intensively studied, its role in tomato fruit growth remains poorly understood. In addition, the relationship between ethylene and the developmental factors NON-RIPENING (NOR) and RIPENING INHIBITOR (RIN) during ripening is under debate. Here, we carried out comprehensive genetic analyses of genome-edited mutants of tomato ETHYLENE INSENSITIVE 2 (SlEIN2), four EIN3-like genes (SlEIL1-4), and three EIN3 BINDING F-box protein genes (SlEBF1-3). Both slein2-1 and the high-order sleil mutant (sleil1 sleil2 sleil3/SlEIL3 sleil4) showed reduced fruit size, mainly due to decreased auxin biosynthesis. During fruit maturation, slein2 mutants displayed the complete cessation of ripening, which was partially rescued by slebf1 but not slebf2 or slebf3. We also discovered that ethylene directly activates the expression of the developmental genes NOR, RIN, and FRUITFULL1 (FUL1) via SlEIL proteins. Indeed, overexpressing these genes partially rescued the ripening defects of slein2-1. Finally, the signal intensity of the ethylene burst during fruit maturation was intimately connected with the progression of full ripeness. Collectively, our work uncovers a critical role of ethylene in fruit growth and supports a molecular framework of ripening control in which the developmental factors NOR, RIN, and FUL1 act downstream of ethylene signaling.
Assuntos
Solanum lycopersicum , Etilenos , Frutas , Regulação da Expressão Gênica de Plantas , Proteínas de PlantasRESUMO
The alternating cell specifications of root epidermis to form hair cells or nonhair cells in Arabidopsis are determined by the expression level of GL2, which is activated by an MYB-bHLH-WD40 (WER-GL3-TTG1) transcriptional complex. The phytohormone ethylene (ET) has a unique effect of inducing N-position epidermal cells to form root hairs. However, the molecular mechanisms underlying ET-induced ectopic root hair development remain enigmatic. Here, we show that ET promotes ectopic root hair formation through down-regulation of GL2 expression. ET-activated transcription factors EIN3 and its homolog EIL1 mediate this regulation. Molecular and biochemical analyses further revealed that EIN3 physically interacts with TTG1 and interferes with the interaction between TTG1 and GL3, resulting in reduced activation of GL2 by the WER-GL3-TTG1 complex. Furthermore, we found through genetic analysis that the master regulator of root hair elongation, RSL4, which is directly activated by EIN3, also participates in ET-induced ectopic root hair development. RSL4 negatively regulates the expression of GL2, likely through a mechanism similar to that of EIN3. Therefore, our work reveals that EIN3 may inhibit gene expression by affecting the formation of transcription-activating protein complexes and suggests an unexpected mutual inhibition between the hair elongation factor, RSL4, and the hair specification factor, GL2. Overall, this study provides a molecular framework for the integration of ET signaling and intrinsic root hair development pathway in modulating root epidermal cell specification.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/crescimento & desenvolvimento , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Proteínas de Ligação a DNA/metabolismo , Etilenos/metabolismo , Fatores de Transcrição/metabolismo , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Diferenciação Celular/genética , Regulação da Expressão Gênica de Plantas , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Complexos Multiproteicos , Epiderme Vegetal/citologia , Epiderme Vegetal/genética , Epiderme Vegetal/crescimento & desenvolvimento , Epiderme Vegetal/metabolismo , Raízes de Plantas/genética , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/metabolismo , Ligação Proteica , Transdução de SinaisRESUMO
Salicylic acid (SA) and ethylene (ET) are important phytohormones that regulate numerous plant growth, development, and stress response processes. Previous studies have suggested functional interplay of SA and ET in defense responses, but precisely how these two hormones coregulate plant growth and development processes remains unclear. Our present work reveals antagonism between SA and ET in apical hook formation, which ensures successful soil emergence of etiolated dicotyledonous seedlings. Exogenous SA inhibited ET-induced expression of HOOKLESS1 (HLS1) in Arabidopsis (Arabidopsis thaliana) in a manner dependent on ETHYLENE INSENSITIVE3 (EIN3) and EIN3-LIKE1 (EIL1), the core transcription factors in the ET signaling pathway. SA-activated NONEXPRESSER OF PR GENES1 (NPR1) physically interacted with EIN3 and interfered with the binding of EIN3 to target gene promoters, including the HLS1 promoter. Transcriptomic analysis revealed that NPR1 and EIN3/EIL1 coordinately regulated subsets of genes that mediate plant growth and stress responses, suggesting that the interaction between NPR1 and EIN3/EIL1 is an important mechanism for integrating the SA and ET signaling pathways in multiple physiological processes. Taken together, our findings illuminate the molecular mechanism underlying SA regulation of apical hook formation as well as the antagonism between SA and ET in early seedling establishment and possibly other physiological processes.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Proteínas de Ligação a DNA/metabolismo , Hipocótilo/crescimento & desenvolvimento , Ácido Salicílico/farmacologia , Fatores de Transcrição/metabolismo , Arabidopsis/efeitos dos fármacos , Arabidopsis/genética , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Genes de Plantas , Hipocótilo/efeitos dos fármacos , Modelos Biológicos , Regiões Promotoras Genéticas , Ligação Proteica/efeitos dos fármacos , Domínios Proteicos , Transcrição Gênica/efeitos dos fármacosRESUMO
Supported alloy catalysts play a pivotal role in many heterogeneous catalytic processes of socioeconomic and environmental importance. But the controlled synthesis of supported alloy nanoparticles with consistent composition and tight size distribution remains a challenging issue. Herein, a simple yet effective method for preparation of highly dispersed, homogeneously alloyed bimetallic nanoparticles on oxide supports is reported. This method is based on solid solution of metal cations in parent oxide and strong electrostatic adsorption of a secondary metal species onto the oxide surface. In the reductive annealing process, hydrogen spillover occurs from the surface metal with a higher reduction potential to the solute metal in solid solution, leading to metal exsolution and homogenous alloying of the metals on the oxide surface. The ceria-supported Ni-Pt alloy is chosen as a model catalyst and hydrazine monohydrate decomposition is chosen as a probe reaction to demonstrate this method, and particularly its advantages over the conventional impregnation and galvanic replacement methods. A systematic application of this method using different oxides and base-noble metal pairs further elucidates its applicability and generality.
Assuntos
Nanopartículas , Óxidos , Ligas , Oxirredução , Metais , HidrogênioRESUMO
BACKGROUND: Long non-coding RNAs (lncRNAs) have been discovered to participate in various cancer developments. However, the biological function of lncRNAs associated with gastric cancer (GC) has not been fully elucidated. METHODS: Quantitative RT-PCR (qRT-PCR) assay was performed to measure lncRNAs, microRNAs (miRNAs) and message RNA (mRNA) expression. Cell Counter Kit-8 (CCK-8), clone formation, wound healing, and transwell assays were performed to investigate cell proliferation, migration, invasion, and apoptosis. Fluorescence in situ hybridization (FISH) assay was used to analyze LINC00922 in either the cytoplasm or nucleus. The potential binding among lncRNA, miRNA, and mRNA was evidenced by bioinformatics, luciferase reporter assay. Mouse-xenograft experiments were used to explore the tumorigenesis in vivo. RESULTS: LINC00922 was upregulated in GC, and high LINC00922 expression was associated with poor prognosis. Inhibition of LINC00922 suppressed GC cell proliferation, migration, invasion, and activated cell apoptosis in vitro and inhibited tumorigenesis in vivo. Besides, LINC00922 was markedly located in the cytoplasm. The mechanistic analysis demonstrated that LINC00922 acted as a sponge of miR-204-5p, thereby inhibiting the expression of the target gene-High Mobility Group AT-hook 2 (HMGA2). CONCLUSION: LINC00922 accelerated the progression of GC by miR-204-5p/HMGA2 axis. These findings support LINC00922 may be a promising option for the diagnosis and therapy of GC.
Assuntos
MicroRNAs , RNA Longo não Codificante , Neoplasias Gástricas , Animais , Carcinogênese/genética , Linhagem Celular Tumoral , Movimento Celular , Proliferação de Células/genética , Regulação Neoplásica da Expressão Gênica , Humanos , Hibridização in Situ Fluorescente , Camundongos , MicroRNAs/genética , MicroRNAs/metabolismo , Oncogenes , RNA Longo não Codificante/genética , RNA Longo não Codificante/metabolismo , RNA Mensageiro/genética , Neoplasias Gástricas/genética , Neoplasias Gástricas/metabolismoRESUMO
The development of a hook-like structure at the apical part of the soil-emerging organs has fascinated botanists for centuries, but how it is initiated remains unclear. Here, we demonstrate with high-throughput infrared imaging and 2-D clinostat treatment that, when gravity-induced root bending is absent, apical hook formation still takes place. In such scenarios, hook formation begins with a de novo growth asymmetry at the apical part of a straightly elongating hypocotyl. Remarkably, such de novo asymmetric growth, but not the following hook enlargement, precedes the establishment of a detectable auxin response asymmetry, and is largely independent of auxin biosynthesis, transport and signaling. Moreover, we found that functional cortical microtubule array is essential for the following enlargement of hook curvature. When microtubule array was disrupted by oryzalin, the polar localization of PIN proteins and the formation of an auxin maximum became impaired at the to-be-hook region. Taken together, we propose a more comprehensive model for apical hook initiation, in which the microtubule-dependent polar localization of PINs may mediate the instruction of growth asymmetry that is either stochastically taking place, induced by gravitropic response, or both, to generate a significant auxin gradient that drives the full development of the apical hook.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Regulação da Expressão Gênica de Plantas , Hipocótilo/metabolismo , Ácidos Indolacéticos/metabolismoRESUMO
BACKGROUND: The purpose of this research is to reveal the improvement effect and potential mechanism of Huagan tongluo Fang (HGTLF) on liver fibrosis. METHODS: A mouse model of liver fibrosis induced by CCl4 was established to analyze the effect of HGTLF on liver fibrosis. The expression changes of miRNA after HGTLF stimulation were detected by qRT-PCR. After interference with miR-184 in Th17 cells, the concentration of IL-17A in cell culture supernatants was detected by ELISA and the proportion of Th17 cells was analyzed by flow cytometry. The relationship between miR-184 and FOXO1 was verified by online software and dual-luciferase reporter system. After HGTLF treatment of Th17 cells overexpressing miR-184, the protein level of FOXO1 was detected by Western blot. RESULTS: HGTLF could significantly improve liver fibrosis in mice. By qRT-PCR, miR-184 was most significantly expressed after HGTLF drug stimulation, and miR-184 was considered to be the major RNA involved in Th17 cell differentiation. Interference with miR-184 in Th17 cells inhibited the differentiation of Th17 cells. By online software and dual-luciferase reporter system assay, the direct interaction of miR-184 with FOXO1 was confirmed. After HGTLF treatment of Th17 cells overexpressing miR-184, FOXO1 protein levels were significantly up-regulated and inhibited the differentiation of Th17 cells, which was reversed by miR-184 inhibitors. The Vivo experiments also confirmed the improvement effect of HGTLF on liver fibrosis in mice. CONCLUSION: Our results indicated that HGTLF could improve liver fibrosis via down-regulating miR-184 and up-regulating of FOXO1 to inhibit Th17 cell differentiation.
Assuntos
Diferenciação Celular , Regulação para Baixo/genética , Medicamentos de Ervas Chinesas/uso terapêutico , Proteína Forkhead Box O1/metabolismo , Cirrose Hepática/tratamento farmacológico , MicroRNAs/genética , Células Th17/citologia , Regulação para Cima/genética , Animais , Sequência de Bases , Tetracloreto de Carbono , Modelos Animais de Doenças , Medicamentos de Ervas Chinesas/farmacologia , Proteína Forkhead Box O1/genética , Cirrose Hepática/genética , Cirrose Hepática/imunologia , Masculino , Camundongos Endogâmicos C57BL , MicroRNAs/metabolismoRESUMO
Root hair elongation relies on polarized cell expansion at the growing tip. As a major osmotically active ion, potassium is expected to be continuously assimilated to maintain cell turgor during hair tip growth. However, due to the lack of practicable detection methods, the dynamics and physiological role of K+ in hair growth are still unclear. In this report, we apply the small-molecule fluorescent K+ sensor NK3 in Arabidopsis root hairs for the first time. By employing NK3, oscillating cytoplasmic K+ dynamics can be resolved at the tip of growing root hairs, similar to the growth oscillation pattern. Cross-correlation analysis indicates that K+ oscillation leads the growth oscillations by approximately 1.5 s. Artificially increasing cytoplasmic K+ level showed no significant influence on hair growth rate, but led to the formation of swelling structures at the tip, an increase of cytosolic Ca2+ level and microfilament depolymerization, implying the involvement of antagonistic regulatory factors (e.g., Ca2+ signaling) in the causality between cytoplasmic K+ and hair growth. These results suggest that, in each round of oscillating root hair elongation, the oscillatory cell expansion accelerates on the heels of cytosolic K+ increment, and decelerates with the activation of antagonistic regulators, thus forming a negative feedback loop which ensures the normal growth of root hairs.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/crescimento & desenvolvimento , Citosol/metabolismo , Antiportadores de Potássio-Hidrogênio/metabolismo , Potássio/metabolismo , Citoesqueleto de Actina/metabolismo , Arabidopsis/citologia , Arabidopsis/metabolismo , Proteínas de Arabidopsis/antagonistas & inibidores , Sinalização do Cálcio , Tamanho Celular/efeitos dos fármacos , Retroalimentação Fisiológica , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/metabolismo , Antiportadores de Potássio-Hidrogênio/antagonistas & inibidores , Bibliotecas de Moléculas Pequenas/farmacologiaRESUMO
Selective decomposition of hydrous hydrazine (N2 H4 â H2 O) over metal catalysts provides a promising means for onboard or portable hydrogen source applications. Studies on N2 H4 â H2 O decomposition catalysts mainly focus on the effects of bulk composition and structure on their performances, instead of the surface-composition-dependent properties. Herein, the synthesis of an Ir-modified Ni/meso-CeO2 catalyst is reported by using a combination of colloidal solution combustion synthesis and galvanic replacement methods. A combination of structural characterization, control experiments, and DFT calculations reveals that the Ni-Ir alloy resulting from calcination treatment exerts a profound effect on the catalytic properties. The resulting Ni@Ni-Ir/meso-CeO2 catalyst shows excellent catalytic performance towards hydrogen generation from N2 H4 â H2 O, which compares favorably with the Ni-Ir bimetallic catalysts reported to date.
RESUMO
Ionic liquids (ILs) have been widely used as environmentally friendly solvents to replace volatile organic solvents in the chemistry industries. They have a high water solubility and potential risk to organisms in the soil-water environment. At present, most studies focused on the batch sorption of ILs in soil and neglected the investigation of IL transports in soil, which results in a lack of understanding of the structure-dependent mobility of ILs in the environment. Laboratory-scale sand/soil column experiments were performed to study the transport of imidazolium-based ILs, such as [C4mim][OTF], [C4mim][TOS], [C4mim][MeSO3], [C4mim][BF4], [C2mim][BF4], and [C6mim][BF4] including different counteranions and alkyl chain lengths of IL cations. Batch experiments were also carried out to compare the difference of sorption distribution coefficient (Kd) between the batch and column experiments. A one-dimensional convective-dispersive model using CXTFIT code was created based on the measured breakthrough curves (BTCs) to estimate the column transport parameters. For the anion, [BF4-], the Kd of ILs in both batch and column experiments increased with increasing alkyl chain lengths of the IL cation. In batch tests, counteranions showed no influence on the Kd of [C4mim][OTF], [C4mim][TOS], [C4mim][MeSO3], [C4mim][BF4], [C2mim][BF4], and [C6mim][BF4]. However, in column tests, the BTCs of 1-butyl-3-methylimidazolium-based ILs were anion dependent as evidenced by the change of retardation factor (R) for different counteranions. Furthermore, the effects of transport distance (11cm, 15cm, 19cm, and 24cm) on the mobility of ILs were estimated. The longer distances signified an increase in the contact time and more binding sites for ILs and therefore, the smoother shapes of BTCs in column experiments.
Assuntos
Imidazóis/análise , Líquidos Iônicos/análise , Modelos Teóricos , Dióxido de Silício/química , Poluentes do Solo/análise , Solo/química , Adsorção , Ânions , Cátions , Imidazóis/química , Líquidos Iônicos/química , Estrutura Molecular , Poluentes do Solo/químicaRESUMO
The growing industrial application of imidazolium-type ionic liquids (ITILs) is likely to result in their release to the environment. Water-soluble ITILs are difficult to remove from wastewaters using traditional adsorbents. In this work, we developed different biochars derived from straw and wood (named as SBB and WBB, respectively) to improve the adsorption effectiveness for removal of ITILs from wastewaters. SBB had high O/C element ratio (0.143), while WBB had high ratio of Vmicro/Vtotal (61.5%) compared with commercial activated carbon (AC). Both of them showed greater adsorption of ITILs than AC with different adsorption mechanisms. FTIR spectra revealed that electrostatic interactions were the dominant driving force in SBB adsorption, while high micropore volume promoted adsorption in WBB. The adsorption of [C2mim][BF4] on SBB and WBB was strongly enhanced by trivalent PO4(3-) anions, suggesting that PO4(3-) anions could be used as promoter to increase the removal efficiency of ITILs from wastewater. Using HCl solution (pH=0.5) as regenerant, SBB and WBB were regenerated with nearly 100% recovery of adsorption capacity over ten consecutive adsorption-desorption cycles. Straw-based biochar and wood-based biochar are efficient sorbents for removal of water-soluble ionic liquids from aqueous solutions.
Assuntos
Carvão Vegetal/química , Imidazóis/isolamento & purificação , Líquidos Iônicos/química , Caules de Planta/química , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Madeira , Adsorção , Biodegradação AmbientalRESUMO
Kinetic, spectroscopic, crystallographic, and computational studies probing a Pd-catalyzed C-H arylation reaction reveal that mono-oxidation of the bis-phosphine ligand is critical for the formation of the active catalyst. The bis-phosphine mono-oxide is shown to be a hemilabile, bidentate ligand for palladium. Isolation of the oxidative addition adduct, with structural elucidation by X-ray analysis, showed that the mono-oxide was catalytically competent, giving the same reaction rate in the productive reaction as the Pd(II)/xantphos precursor. A dual role for the carboxylate base in both catalyst activation and reaction turnover was demonstrated, along with the inhibiting effect of excess phosphine ligand. The generality of the role of phosphine mono-oxide complexes in Pd-catalyzed coupling processes is discussed.
Assuntos
Paládio/química , Fosfinas/química , Xantenos/química , Catálise , Cristalografia por Raios X , Cinética , Espectroscopia de Ressonância Magnética , OxirreduçãoRESUMO
The natural oxidation of biochar in the environment has been widely observed. However, its influence on the sorption of organic contaminants remains poorly understood. In the present study, a series of wood-based biochars prepared between 300 and 600°C (referred to as BC300-BC600) was abiotically incubated for one year to examine the aging effect of the temperature series of biochars on their sorption of aromatic cationic herbicides (ACHs, paraquat and diquat) as well as a nonpolar reference adsorbate (naphthalene). One year of oxidation showed no obvious effect on the surface area, but distinct increases in the O/C elemental ratio, density of the surface groups and cation exchange capacity (CEC) were observed. Therefore, these properties were significantly affected by the charring temperature. After incubation, high-temperature biochars (BC500 and BC600) displayed a 14.1-36.3% decrease in the sorption (qm) of ACHs. The alteration of their sorption tendency was similar to the reduced sorption of naphthalene on oxidized biochars, in which the increased surface groups lowered the surface area accessible to adsorbates because of blockage by adsorbed water molecule clusters. Conversely, a pronounced increase of ACHs sorption by 121.7-201.1% on the low-temperature biochar (BC300) was observed, presumably due to the increase of CEC values after oxidation. This result was further demonstrated by a significant linear relationship between the paraquat sorption (qm) and CEC values (R(2)=0.9895) of oxidized biochars. Interestingly, one year of oxidation simultaneously resulted in an enhanced sorption of paraquat and a reduced sorption of diquat on BC400, which indicated that the oxidation-induced sorption change of ACHs is a complex function of changes in the surface properties of the biochars as well as the molecular structure of the solute.
Assuntos
Carvão Vegetal/química , Poluentes Ambientais/química , Herbicidas/química , Temperatura Alta , Adsorção , Cátions , Naftalenos/química , Oxirredução , Madeira/químicaRESUMO
Degraded mulch pollution is of a great concern for agricultural soils. Although numerous studies have examined this issue from an environmental perspective, there is a lack of research focusing on crop-specific factors such as crop type. This study aimed to explore the correlation between meteorological and crop factors and mulch contamination. The first step was to estimate the amounts of mulch-derived microplastics (MPs) and phthalic acid esters (PAEs) during the rapid expansion period (1993-2012) of mulch usage in China. Subsequently, the Elastic Net (EN) and Random Forest (RF) models were employed to process a dataset that included meteorological, crop, and estimation data. At the national level, the RF model suggested that coldness in fall was crucial for MPs generation, while vegetables acted as a key factor for PAEs release. On a regional scale, the EN results showed that crops like vegetables, cotton, and peanuts remained significantly involved in PAEs contamination. As for MPs generation, coldness prevailed over all regions. Aridity became more critical for southern regions compared to northern regions due to solar radiation. Lastly, each region possessed specific crop types that could potentially influence its MPs contamination levels and provide guidance for developing sustainable ways to manage mulch contamination.
Assuntos
Ácidos Ftálicos , Poluentes do Solo , Ácidos Ftálicos/análise , Plásticos , Poluentes do Solo/análise , Agricultura , Solo , Verduras , Microplásticos , China , Ésteres/análiseRESUMO
Colloidal interactions between clay minerals and microplastics (MPs) in high salinity seawater are crucial for determining MP fate in marine environments. Montmorillonite (MMT) forms thin and pliable films that tightly cover MPs, while the thick and rigid lamellae of kaolinite (KLT) have limited contact with MPs, resulting in unstable bonding. However, a small quantity of small-sized KLT can create relatively stable heteroaggregates by embedding into the interstitial spaces of MPs. Both MMT and KLT colloids can decrease the mobility of MPs in seawater-saturated sea sand, but their breakthrough curves (BTCs) show distinct phenomena of "blocking" and "ripening", respectively. The "blocking" phenomenon occurs when flexible MMT adheres to the sand surface, depleting attachment sites quickly and inhibiting the retention of subsequent heteroaggregates of MMT-wrapped MPs. The transport of single MMT also experiences colloid competition for attachment sites, but pre-equilibration experiments reveal no competition between MMT and bare MPs for attachment sites. Instead, the attached MMT provides additional attachment sites for MPs. These results suggest that the wrapping of MPs by MMT plays a dominant role in the "blocking" of cotransport. In contrast, rigid KLT forms a three-dimensional stack on the sand surface, offering more attachment sites for subsequent MPs and heteroaggregates.
Assuntos
Bentonita , Argila , Microplásticos , Água do Mar , Poluentes Químicos da Água , Microplásticos/química , Argila/química , Porosidade , Água do Mar/química , Bentonita/química , Poluentes Químicos da Água/química , Caulim/química , Minerais/química , Coloides/químicaRESUMO
Polymer chain extenders, commonly used in plastic production, have garnered increasing attention due to their potential environmental impacts. However, a comprehensive understanding of their ecological risks remains largely unknown. In this study, we employed the model organism Caenorhabditis elegans to investigate toxicological profiles of ten commonly-used chain extenders. Exposure to environmentally relevant concentrations of these chain extenders (ranging from 0.1 µg L-1 to 10 mg L-1) caused significant variations in toxicity. Lethality assays demonstrated the LC50 values ranged from 92.42 µg L-1 to 1553.65 mg L-1, indicating marked differences in acute toxicity. Sublethal exposures could inhibit nematodes' growth, shorten lifespan, and induce locomotor deficits, neuronal damage, and reproductive toxicity. Molecular analyses further elucidated the involvement of the DAF-16 and SKN-1 signaling pathways, as evidenced by upregulated expression of genes including ctl-1,2,3, sod-3, gcs-1, and gst-4. It implicates these pathways in mediating oxidative stress and toxicities induced by chain extenders. Particularly, hexamethylene diisocyanate and diallyl maleate exhibited markedly high toxicity among the chain extenders, as revealed through a comparative analysis of multiple endpoints. These findings demonstrate the potential ecotoxicological risks of polymer chain extenders, and suggest the need for more rigorous environmental safety assessments.
Assuntos
Proteínas de Caenorhabditis elegans , Caenorhabditis elegans , Proteínas de Ligação a DNA , Fatores de Transcrição Forkhead , Transdução de Sinais , Fatores de Transcrição , Animais , Caenorhabditis elegans/efeitos dos fármacos , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Fatores de Transcrição/metabolismo , Fatores de Transcrição/genética , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Fatores de Transcrição Forkhead/metabolismo , Fatores de Transcrição Forkhead/genética , Transdução de Sinais/efeitos dos fármacos , Polímeros/toxicidade , Polímeros/química , Longevidade/efeitos dos fármacosRESUMO
This study examined the distinct effects of algae polysaccharides (AP), namely sodium alginate (SA), fucoidan (FU), and laminarin (LA), on the aggregation of nanoplastics (NP) in seawater, as well as their subsequent transport in seawater-saturated sea sand. The pristine 50 nm NP tended to form large aggregates, with an average size of approximately 934.5 ± 11 nm. Recovery of NP from the effluent (Meff) was low, at only 18.2 %, and a ripening effect was observed in the breakthrough curve (BTC). Upon the addition of SA, which contains carboxyl groups, the zeta (ζ)-potential of the NP increased by 2.8 mV. This modest enhancement of electrostatic interaction with NP colloids led to a reduction in the aggregation size of NP to 598.0 ± 27 nm and effectively mitigated the ripening effect observed in the BTC. Furthermore, SA's adherence to the sand surface and the resulting increase in electrostatic repulsion, caused a rise in Meff to 27.5 %. In contrast, the introduction of FU, which contains sulfate ester groups, resulted in a surge in ζ-potential of the NP to -27.7 ± 0.76 mV. The intensified electrostatic repulsion between NP and between NP and sand greatly increased Meff to 45.6 %. Unlike the effects of SA and FU, the addition of LA, a neutral compound, caused a near disappearance of ζ-potential of NP (-3.25 ± 0.68 mV). This change enhanced the steric hindrance effect, resulting in complete stabilization of particles and a blocking effect in the BTC of NP. Quantum chemical simulations supported the significant changes in the electrostatic potential of NP colloids induced by SA, FU and LA. In summary, the presence of AP can induce variability in the mobility of NP in seawater-saturated porous media, depending on the nature of the weak, strong, or non-electrostatic interactions between colloids, which are influenced by the structure and functionalization of the polysaccharides themselves. These findings provide valuable insights into the complex and variable behavior of NP transport in the marine environment.
Assuntos
Polissacarídeos , Água do Mar , Polissacarídeos/química , Água do Mar/química , Porosidade , Alginatos/química , Microplásticos/química , Eletricidade EstáticaRESUMO
The isoquinolinamide series of HCV NS5A inhibitors exemplified by compounds 2b and 2c provided the first dual genotype-1a/1b (GT-1a/1b) inhibitor class that demonstrated a significant improvement in potency toward GT-1a replicons compared to that of the initial program lead, stilbene 2a. Structure-activity relationship (SAR) studies that uncovered an alternate phenylglycine-based cap series that exhibit further improvements in virology profile, along with some insights into the pharmacophoric elements associated with the GT-1a potency, are described.
Assuntos
Antivirais/química , Glicina/análogos & derivados , Hepacivirus/enzimologia , Proteínas não Estruturais Virais/antagonistas & inibidores , Animais , Antivirais/síntese química , Antivirais/farmacocinética , Cristalografia por Raios X , Avaliação Pré-Clínica de Medicamentos , Genótipo , Glicina/síntese química , Glicina/química , Glicina/farmacocinética , Meia-Vida , Hepacivirus/genética , Hepacivirus/fisiologia , Microssomos Hepáticos/metabolismo , Conformação Molecular , Ratos , Relação Estrutura-Atividade , Proteínas não Estruturais Virais/metabolismo , Replicação Viral/efeitos dos fármacosRESUMO
In a recent disclosure, we described the discovery of dimeric, prolinamide-based NS5A replication complex inhibitors exhibiting excellent potency towards an HCV genotype 1b replicon. That disclosure dealt with the SAR exploration of the peripheral region of our lead chemotype, and herein is described the SAR uncovered from a complementary effort that focused on the central core region. From this effort, the contribution of the core region to the overall topology of the pharmacophore, primarily vector orientation and planarity, was determined, with a set of analogs exhibiting <10 nM EC(50) in a genotype 1b replicon assay.