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1.
Aging (Albany NY) ; 122020 May 11.
Artigo em Inglês | MEDLINE | ID: mdl-32392533

RESUMO

Aging is closely associated with atherosclerosis. Macrophages accumulate in atherosclerotic lesions contributing to the development and progression of atherosclerosis. Although atherosclerotic lesions are known to contain senescent cells, the mechanism underlying the formation of senescent macrophages during atherosclerosis is still unclear. In this study, macrophages with different origins were collected, including THP-1 macrophages, telomerase reverse transcriptase knock out (Tert-/-) mouse peritoneal macrophages, and human peripheral blood mononuclear cells (PBMCs). We found Lipopolysaccharide (LPS) could induce the formation of senescent macrophages, which was typified by the morphological changes, senescence-associated secretory phenotype (SASP) secretory, and persistent DNA damage response. Mechanistically, bromodomain-containing protein 4 (BRD4), a chromosomal binding protein related to gene expression, was found to play a key role in the pathological process, which could offer new therapeutic perspectives. Inhibition of BRD4 by siBRD4 or inhibitors such as JQ-1 or I-BET762 prevented the aging of macrophages and lipid accumulation in the LPS-induced senescent macrophages by decreasing expression of SASP in autocrine and paracrine senescence. These findings have significant implications for the understanding of the pathobiology of age-associated diseases and may guide future studies on targeted clinical drug therapy.

2.
Dev Comp Immunol ; 110: 103720, 2020 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-32344046

RESUMO

The silkworm, Bombyx mori, is utilized as a research model in many aspects of biological studies, including genetics, development and immunology. Previous biochemical and genomic studies have elucidated the silkworm immunity in response to infections elicited by bacteria, fungi, microsporidia, and viruses. The intestine serves as the front line in the battle between insects and ingested harmful microorganisms. In this study, we performed RNA sequencing (RNA-seq) of the larval silkworm midgut after oral infection with the Gram-positive bacterium Bacillus bombysepticus and the Gram-negative bacterium Yersinia pseudotuberculosis. This enables us to get a comprehensive understanding of the midgut responses to bacterial infection. We found that B. bombysepticus induced much stronger immune responses than Y. pseudotuberculosis did. Bacterial infection resulted in more energy consumption including carbohydrates and fatty acids. The midgut immune system was characterized by the generation of reactive oxygen species and antimicrobial peptides. The former played a critical role in eliminating invading bacteria during early stage, while the latter executed during late stage. Our results provide an integrated insight into the midgut systematic responses to bacterial infection.

3.
Insect Biochem Mol Biol ; 121: 103374, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32283278

RESUMO

DNA methylation plays important roles in the behavioral plasticity of animals. The migratory locust, Locusta migratoria, displays striking density-dependent phenotypic plasticity that can reversely transit between solitarious and gregarious phases. However, the role and the mechanism through which DNA methylation is involved in locust phase change remain unknown. Here, we investigated the expression levels of three DNA methyltransferase genes and their roles in the regulation of locust phase changes. All three Dnmt genes, namely, Dnmt1, Dnmt2 and Dnmt3 showed high expression levels in the brains of gregarious locusts. By contrast, only Dnmt3 transcript rapidly responded to population density changes, decreasing during the isolation of gregarious locusts and steadily increasing upon the crowding of solitarious locusts. Dnmt3 knockdown significantly reduced the phase-related locomotor activity, rather than the attraction index, in gregarious and crowded solitarious locusts. Transcriptome analysis showed that Dnmt3 knockdown upregulated the genes related to metabolism and transporting activity and downregulated those associated with oxidative stress response. The expression level of the phase-core transcriptional factor, hormone receptor HR3, was significantly suppressed in the brain after Dnmt3 knockdown. Moreover, there was significant overlap in the differentially expressed genes between Dnmt3 RNAi and HR3 RNAi data sets, suggesting HR3 may act as key transcriptional factor mediating Dnmt3-controlled gene expression profiles in locust brains. These findings suggest that Dnmt3 transcription is involved in locust behavioral transition, implying the possible roles of DNA methylation in phase-related phenotypic plasticity in locusts.

4.
Dev Comp Immunol ; 108: 103675, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32173445

RESUMO

Female parasitoid wasps normally inject virulence factors together with eggs into their host to counter host immunity defenses. A newly identified RhoGAP protein in the venom of Microplitis mediator compromises the cellular immunity of its host, Helicoverpa armigera. RhoGAP1 proteins entered H. armigera hemocytes, and the host cellular cytoskeleton was disrupted. Depletion of MmGAP1 by injection of dsRNA or antibody increased the wasp egg encapsulation rate. An immunoprecipitation assay of overexpressed MmGAP1 protein in a Helicoverpa cell line showed that MmGAP1 interacts with many cellular cytoskeleton associated proteins as well as Rho GTPases. A yeast two-hybrid and a pull-down assay demonstrated that MmGAP1 interacts with H. armigera RhoA and Cdc42. These results show that the RhoGAP protein in M. mediator can destroy the H. armigera hemocyte cellular cytoskeleton, restrain host cellular immune defense, and increase the probability of successful parasitism.

5.
Dev Comp Immunol ; 108: 103688, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32222357

RESUMO

Lepidopteran insects have potent innate immunity to fight against the invading pathogens. As the initiation step, pattern recognition receptors (PRRs) recognize and bind microbial surface configurations known as pathogen-associated molecular patterns (PAMPs). Aftermath, they initiate both cellular and humoral immune responses, including phagocytosis, agglutination, nodulation, encapsulation, prophenoloxidase activation, and synthesis of antimicrobial peptides. In this review, we summarize the recent findings concerning PRRs in lepidoptaeran insects, mostly agriculture pests including Helicoverpa armigera, Plutella xylostella, and Spodoptera exigua. We mainly focus on the function and phylogeny of C-type lectins (CTLs), peptidoglycan recognition proteins (PGRPs), ß-1,3-glucan recognition proteins (ßGRPs), and galectins (GALEs). It enriches our understanding of the immune system of lepidopteran insects and provides directions in the future research.

6.
Chem Commun (Camb) ; 2020 Mar 17.
Artigo em Inglês | MEDLINE | ID: mdl-32181461

RESUMO

Catalytic conversion of carbon dioxide (CO2) to value-added chemicals under mild conditions is highly desired, albeit with significant challenges. Here, in terms of exposure of abundant active sites and excellent photo-to-thermal conversion properties, flower-like Co2C has been firstly used for effectively catalysing the cycloaddition of CO2 with epoxides to produce cyclic carbonates with yields of up to 95% under solar light. Density functional theory (DFT) calculations reveal that Lewis acid sites of the surface Co atoms can activate both CO2 and epoxide, thus opening up the possibility of a CO2-epoxide cycloaddition reaction.

7.
Circulation ; 141(12): 984-1000, 2020 Mar 24.
Artigo em Inglês | MEDLINE | ID: mdl-31902237

RESUMO

BACKGROUND: S-nitrosylation (SNO), a prototypic redox-based posttranslational modification, is involved in the pathogenesis of cardiovascular disease. The aim of this study was to determine the role of SNO of MLP (muscle LIM protein) in myocardial hypertrophy, as well as the mechanism by which SNO-MLP modulates hypertrophic growth in response to pressure overload. METHODS: Myocardial samples from patients and animal models exhibiting myocardial hypertrophy were examined for SNO-MLP level using biotin-switch methods. SNO sites were further identified through liquid chromatography-tandem mass spectrometry. Denitrosylation of MLP by the mutation of nitrosylation sites or overexpression of S-nitrosoglutathione reductase was used to analyze the contribution of SNO-MLP in myocardial hypertrophy. Downstream effectors of SNO-MLP were screened through mass spectrometry and confirmed by coimmunoprecipitation. Recruitment of TLR3 (Toll-like receptor 3) by SNO-MLP in myocardial hypertrophy was examined in TLR3 small interfering RNA-transfected neonatal rat cardiomyocytes and in a TLR3 knockout mouse model. RESULTS: SNO-MLP level was significantly higher in hypertrophic myocardium from patients and in spontaneously hypertensive rats and mice subjected to transverse aortic constriction. The level of SNO-MLP also increased in angiotensin II- or phenylephrine-treated neonatal rat cardiomyocytes. S-nitrosylated site of MLP at cysteine 79 was identified by liquid chromatography-tandem mass spectrometry and confirmed in neonatal rat cardiomyocytes. Mutation of cysteine 79 significantly reduced hypertrophic growth in angiotensin II- or phenylephrine-treated neonatal rat cardiomyocytes and transverse aortic constriction mice. Reducing SNO-MLP level by overexpression of S-nitrosoglutathione reductase greatly attenuated myocardial hypertrophy. Mechanistically, SNO-MLP stimulated TLR3 binding to MLP in response to hypertrophic stimuli, and disrupted this interaction by downregulating TLR3-attenuated myocardial hypertrophy. SNO-MLP also increased the complex formation between TLR3 and RIP3 (receptor-interacting protein kinase 3). This interaction in turn induced NLRP3 (nucleotide-binding oligomerization domain-like receptor pyrin domain containing 3) inflammasome activation, thereby promoting the development of myocardial hypertrophy. CONCLUSIONS: Our findings revealed a key role of SNO-MLP in myocardial hypertrophy and demonstrated TLR3-mediated RIP3 and NLRP3 inflammasome activation as the downstream signaling pathway, which may represent a therapeutic target for myocardial hypertrophy and heart failure.

8.
Chem Biodivers ; 17(1): e1900516, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31725193

RESUMO

In this study, 13 panaxadiol (PD) derivatives were synthesized via reactions with aromatic compounds and amino acids. Following this, the cytotoxicity of these compounds was evaluated against four cancer cell lines (human hepatoma cells HepG-2, human lung cancer cells A549, human breast cancer cells MCF-7, and human colon cancer cells HCT-116) and one normal cell lines (human gastric epithelial cells GES-1). The results showed that the panaxadiol derivatives 3, 12, and 13 showed significant inhibition of cellular proliferation against cancer cells compared with PD, and the panaxadiol derivative 12 had the lowest IC50 value for A549 (IC50 =18.91±1.03 µm). For MCF-7 cells, most compounds exhibited good inhibition of cellular proliferation, and the panaxadiol derivative 13 showed the strongest inhibitory effect (IC50 =8.62±0.23 µm), which significantly increased the cytotoxicity of PD and was stronger than the positive control (mitomycin). For normal cells, all compounds exhibited low or no toxic effects; thus, these derivatives can be used to develop novel antiproliferative agents.


Assuntos
Antineoplásicos/síntese química , Antineoplásicos/farmacologia , Ginsenosídeos/química , Ginsenosídeos/farmacologia , Antineoplásicos/química , Linhagem Celular , Proliferação de Células/efeitos dos fármacos , Relação Dose-Resposta a Droga , Ensaios de Seleção de Medicamentos Antitumorais , Ginsenosídeos/síntese química , Humanos , Estrutura Molecular , Relação Estrutura-Atividade
9.
Arterioscler Thromb Vasc Biol ; 40(1): 175-188, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31694393

RESUMO

OBJECTIVE: Thoracic aortic dissection (TAD) is a fatal disease that leads to aortic rupture and sudden death. However, little is known about the effect and molecular mechanism of S-nitrosylation (SNO) modifications in TAD formation. Approach and Results: SNO levels were higher in aortic tissues from TAD patients than in those from healthy controls, and PLS3 (plastin-3) SNO was identified by liquid chromatography-tandem mass spectrometry analysis. Furthermore, tail vein administration of endothelial-specific adeno-associated viruses of mutant PLS3-C566A (denitrosylated form) suppressed the development of TAD in mice, but the wild-type PLS3 (S-nitrosylated form) virus did not. Mechanistically, Ang II (angiotensin II)-induced PLS3 SNO enhanced the association of PLS3 with both plectin and cofilin via an iNOS (inducible nitric oxide synthase)-dependent pathway in endothelial cells. The formation of PLS3/plectin/cofilin complex promoted cell migration and tube formation but weakened adherens junction formation in Ang II-treated endothelial cells. Interestingly, denitrosylated form of PLS3 partially mitigated Ang II-induced PLS3/plectin/cofilin complex formation and cell junction disruption. Additionally, the inhibition of iNOS attenuated PLS3 SNO and the association of PLS3 with plectin and cofilin, thereby modulating endothelial barrier function. CONCLUSIONS: Our data indicate that protein SNO modification in endothelial cells modulates the progression of aortic aneurysm and dissection. The iNOS-mediated SNO of PLS3 at the Cys566 site promoted its interaction with cofilin and plectin, thus contributing to endothelial barrier disruption and pathological angiogenesis in TAD.

10.
Arch Insect Biochem Physiol ; 103(2): e21629, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31599031

RESUMO

Parasitoids serve as effective biocontrol agents for agricultural pests. However, they face constant challenges from host immune defense and numerous pathogens and must develop potent immune defense against these threats. Despite the recent advances in innate immunity, little is known about the immunological mechanisms of parasitoids. Here, we identified and characterized potential immune-related genes of the endoparasitoid, Pteromalus puparum, which act in regulating populations of some members of the Pieridae. We identified 216 immune-related genes based on interrogating the P. puparum genome and transcriptome databases. We categorized the cognate gene products into recognition molecules, signal moieties and effector proteins operating in four pathways, Toll, IMD, JAK/STAT, and JNK. Comparative analyses of immune-related genes from seven insect species indicate that recognition molecules and effector proteins are more expanded and diversified than signaling genes in these signal pathways. There are common 1:1 orthologs between the endoparasitoid P. puparum and its relative, the ectoparasitoid Nasonia vitripennis. The developmental expression profiles of immune genes randomly selected from the transcriptome analysis were verified by a quantitative polymerase chain reaction. Our work provides comprehensive analyses of P. puparum immune genes, some of which may be exploited in advancing parasitoid-based biocontrol technologies.


Assuntos
Proteínas de Transporte/genética , Imunidade Inata/genética , Proteínas de Insetos/genética , Transdução de Sinais/imunologia , Vespas/genética , Sequência de Aminoácidos , Animais , Proteínas de Transporte/química , Proteínas de Transporte/metabolismo , Embrião não Mamífero/química , Embrião não Mamífero/metabolismo , Feminino , Perfilação da Expressão Gênica , Proteínas de Insetos/química , Proteínas de Insetos/metabolismo , Larva/genética , Larva/metabolismo , Masculino , Filogenia , Pupa/genética , Pupa/metabolismo , Alinhamento de Sequência , Vespas/crescimento & desenvolvimento , Vespas/metabolismo , Vespas/fisiologia
11.
Water Environ Res ; 2019 Oct 23.
Artigo em Inglês | MEDLINE | ID: mdl-31646692

RESUMO

To determine the effect of different agents on the dynamic characteristics of floc structures, ferric chloride (FC) and anionic polyacrylamide (APAM) were dosed as coagulant and flocculant, respectively, to flocculate the coal slime water. Particle vision and measurement (PVM) was employed to monitor the flocculation process in situ. The results showed that the floc could grow to a size of approximately 1 mm only under conditions of 100 mg/L FC and 50 mg/L APAM. The coagulant dosage influenced either the aggregation of the slime particles or the conformation of the flocculant. If the coagulants were insufficient or excessive, the flocculant conformations were stretch chains and resembled unable to bridging the slime particles as shown in the captured images. The variation of the relative backscatter index (RBI) during the process indicated that the required residence time for flocculation was proportional to the ratio of particle size at the end of flocculation to that at the beginning of the process. It can be concluded that PVM is an effective instrument that can obtain useful dynamic information of the flocculation process by combining real-time images and the RBI. PRACTITIONER POINTS: The coagulant concentration affects the conformation of the flocculant. The required retention time is depended on the max size that flocs can reach. PVM is a powerful instrument for studying dynamic flocculation process in situ.

12.
Opt Express ; 27(16): 23476-23485, 2019 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-31510624

RESUMO

Recent experimental research has reported that a surface electric field on the polymer solar cell can restrain the recombination of the resultant charged carriers [23]. Based on this, this article reveals an underlying mechanism: If a surface electric field below 4.5 × 104 V/cm is applied to the polymer layer, the electric field drives the charged polaron to transport. Once the polaron approaches and collides with the exciton, it is easily trapped by the potential well produced by the exciton and then forms a charged exciton. The decay of the resultant charged exciton rapidly reduces the number of excitons. However, once the external field surpasses the threshold value of 4.5 × 104 V/cm, the charged polaron absorbs momentum from the external electric field and shakes off the trapping of the exciton. It finally steps out of the original lattice potential well, where the appropriate electric field magnitude ranges from 5.5 × 104 V/cm to 8 × 105 V/cm. After a collision of 300 fs, apart from a phase shift, the exciton still exists. Then, the originally carriers is dissociated when the electric field reaches 0.8 MV/cm. The applied surface field is able to effectively keep the excitons from fusion with the transporting charged polarons, which provides a valid and easily manufactured approach to yield higher efficiency of polymer solar cells.

13.
Iran J Pharm Res ; 18(2): 914-921, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31531073

RESUMO

A rapid and simple method has been developed for the screening and identification of natural antioxidants from the leaves of Acer ginnala Maxim (AG). The process is that upon reaction with 1,1-diphenyl-2-picrylhydrazyl (DPPH), the white yellow spots of compounds with potential antioxidant effects will be significantly observed on the thin-layer chromatography (TLC), and possible structures will be presumed by the ESI/MS technique. Using the improved approach, 6 compounds in the AG extract were found to possess a potential antioxidant activity. They were speculated as quercetin-3-O-α-L-(3"-galloyl)-rhamnoside (1), quercetin-3-O-α-L-(2"-galloyl)-rhamnoside (2), quercetin-3-O-α-L-(2"-galloyl)-arabinopyranoside (3), acertannin (4), gallic acid (5), and methyl gallate (6). In addition, we were still found that compounds 2, 3, and 5 had favorable antioxidant activity from the scannogram of the DPPH reaction plate. As a result, the isolated 6 compounds structures were in accordance with the presumed structures. Furthermore, the free radical scavenging capacities of the available identified compounds were also investigated. Compounds 2, 3, and 5 showed significant DPPH.Scavenging capacities, with IC50 values of 2.83 µg/mL, 2.34 µg/mL, and 1.86µg/mL, respectively. The results indicated that this newly improved method could be widely applied for rapid screening and identification of natural antioxidants from Chinese herbal medicines.

14.
Artigo em Inglês | MEDLINE | ID: mdl-31514124

RESUMO

Detecting segments of interest from videos is a common problem for many applications. And yet it is a challenging problem as it often requires not only knowledge of individual target segments, but also contextual understanding of the entire video and the relationships between the target segments. To address this problem, we propose the Sequence-to-Segments Network (S2N), a novel and general end-to-end sequential encoder-decoder architecture. S2N first encodes the input video into a sequence of hidden states that capture information progressively, as it appears in the video. It then employs the Segment Detection Unit (SDU), a novel decoding architecture, that sequentially detects segments. At each decoding step, the SDU integrates the decoder state and encoder hidden states to detect a target segment. During training, we address the problem of finding the best assignment of predicted segments to ground truth using the Hungarian Matching Algorithm with Lexicographic Cost. Additionally, we propose to use the squared Earth Mover's Distance to optimize the localization errors of the segments. We show the state-of-the-art performance of S2N across numerous tasks, including video highlighting, video summarization, and human action proposal generation.

15.
Med Sci Monit ; 25: 5953-5960, 2019 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-31399554

RESUMO

BACKGROUND Screw penetration into the hip joint is a severe complication during acetabular fracture surgery. The standard fluoroscopic views of the pelvis cannot provide adequate safety during screw insertion. The aim of this research was to determine and evaluate the accuracy of the acetabular lateral view for screw placement. MATERIAL AND METHODS Twenty screws were randomly chosen and intentionally penetrated into the articular surface (1-2 mm), and the remaining 20 screws were extra-articular ones positioned in close proximity to the articular surface. Three surgeons, each evaluating 40 screws, provided a total of 120 rated observations for each screw position. We compared the traditional view or combined with lateral acetabular view with the criterion standard based on unaided visual assessment. A blinded and independent review of each pelvic intraoperative fluoroscopy was made by 3 independent observers. Specificity, sensitivity, positive predictive value, negative predictive value, correct interpretation, intra-class correlation coefficients (ICC), and Youden index were calculated. RESULTS There were significant differences in sensitivity, NPV, correct interpretation, and Youden index between the 2 groups (P<0.05). The ICC was 0.531 when the antero-posterior, iliac, and obturator oblique views were used. The ICC was remarkably increased when using a combination of the ''lateral'' view and the standard views for screw perforation of the joint. CONCLUSIONS Use of the lateral view of the acetabulum can be a complementary method to identify malpositioned screws, and it helps increase the accuracy rate of inserting screws in the treatment of posterior wall fracture.


Assuntos
Acetábulo/diagnóstico por imagem , Fixação Interna de Fraturas/métodos , Fraturas Ósseas/cirurgia , Acetábulo/lesões , Acetábulo/cirurgia , Adulto , Idoso , Parafusos Ósseos , Cadáver , Fluoroscopia/métodos , Fraturas do Quadril , Humanos , Masculino , Pessoa de Meia-Idade , Pelve/cirurgia , Cirurgia Assistida por Computador/métodos
16.
Insect Sci ; 2019 Jul 18.
Artigo em Inglês | MEDLINE | ID: mdl-31317624

RESUMO

Recently, parasitoid wasp species Microplitis mediator has evoked increasing research attention due to its possible use in the control of Lepidoptera insects. Because insect development involves changes in cuticle composition, identification and expression analysis of M. mediator cuticular proteins may clarify the mechanisms involved in parasite development processes. We found 70 cuticular proteins from the M. mediator transcriptome and divided them into seven distinct families. Expression profiling indicated that most of these cuticular protein genes have expression peaks specific for one particular developmental stage of M. mediator. Eggs and pupae have the highest number of transcriptionally active cuticular protein genes (47 and 52 respectively). Only 12 of these genes maintained high expression activity during late larval development. Functional analysis of two larval proteins, MmCPR3 and MmCPR14, suggested their important role in the proper organization of the cuticle layers of larvae. During M. mediator larval development, normal cuticle formation can be supported by a limited number of cuticular proteins.

17.
Chem Biodivers ; 16(8): e1900188, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31298488

RESUMO

Panaxadiol is a dammarane-type ginsenoside having high ginseng content. The 3-hydroxy group of panaxadiol (PD) was modified by fatty acids and diacids. The modified panax glycol had enhanced anticancer activity. Twelve PD derivatives were evaluated and purified by chemical synthesis, column chromatography, co-synthesis, and identification. The human leukemia cells THP-1, HL-60, and human prostate cancer cell lines PC-3 were evaluated; PD derivatives were tested and evaluated in vitro by MTT assay. The results showed that the antitumor activities of some derivatives on three tumor cell lines were better than those of PD.


Assuntos
Antineoplásicos Fitogênicos/farmacologia , Proliferação de Células/efeitos dos fármacos , Ginsenosídeos/química , Panax/química , Antineoplásicos Fitogênicos/síntese química , Antineoplásicos Fitogênicos/química , Linhagem Celular Tumoral , Ginsenosídeos/síntese química , Ginsenosídeos/farmacologia , Células HL-60 , Humanos , Células PC-3 , Panax/metabolismo
18.
Inorg Chem ; 58(15): 10390-10398, 2019 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-31342744

RESUMO

Four Hg-based IR nonlinear-optical materials, AHgSnQ4 (A = Sr, Ba; Q = S, Se), were discovered and investigated systematically. Their structures are built of two-dimensional [HgSnQ4]2- layers, which are assembled alternately by distorted (HgQ4 and SnQ4) tetrahedra and separated by eight-coordinated A2+ cations. The two sulfides AHgSnS4 (A = Ba, Sr) exhibit large second-harmonic-generation (SHG) responses (2.8 and 1.9 × AgGaS2 at 2.09 µm), as well as large band gaps (2.77 and 2.72 eV). The two selenides AHgSnSe4 (A = Ba, Sr) show even stronger SHG responses, about 5 times that of AgGaS2. Furthermore, all four compounds show phase-matching behavior, and the results of first-principles calculation elucidate the key role of the HgQ4 group in the enhanced SHG effect in ß-BaHgSnS4 and BaHgSnSe4.

19.
J Am Chem Soc ; 141(23): 9134-9139, 2019 Jun 12.
Artigo em Inglês | MEDLINE | ID: mdl-31131600

RESUMO

The flexible organic amine cations on the interfaces of two-dimensional (2D) hybrid organic-inorganic perovskite nanosheets could form relaxed structures, which would lead to exotic optoelectronic properties but are hard to understand. Here, the unusual interfacial relaxation of nanosheets exfoliated from an orthorhombic 2D lead halide perovskite, [(C6H5CH2NH3)2]PbCl4, is interrogated via ultrafast second-harmonic generation (SHG) spectroscopy. The in-plane SHG intensity anisotropy of these nanosheets is found to decrease with reducing layer thickness. Combined first-principles calculations and Monte Carlo simulations reveal that the induced second-order polarization arises primarily from the (C6H5CH2NH3)+ cations; and these organic amine cations form significantly reorganized conformations with decreasing nanosheet thickness due to weakened van der Waals interactions. Because the orientations of organic components at the interface determine their electric properties and specifically the dipolar susceptibility, the resulting structure leads to striking changes in the SHG properties.

20.
Philos Trans R Soc Lond B Biol Sci ; 374(1767): 20180323, 2019 03 04.
Artigo em Inglês | MEDLINE | ID: mdl-30967022

RESUMO

Reactive oxygen species (ROS) play important roles in defence response of host plants versus pathogens. While generation and detoxification of ROS is well understood, how varied ability of different isolates of pathogens to overcome host ROS, or ROS contribution to a particular isolate's pathogenicity, remains largely unexplored. Here, we report that transcriptional regulation of the ROS pathway, in combination with the insulin pathway, increases the pathogenicity of invasive species Bursaphelenchus xylophilus. The results showed a positive correlation between fecundity and pathogenicity of different nematode isolates. The virulent isolates from introduced populations in Japan, China and Europe had significantly higher fecundity than native avirulent isolates from the USA. Increased expression of Mn-SOD and reduced expression of catalase/ GPX-5 and H2O2 accumulation during invasion are associated with virulent strains. Additional H2O2 could improve fecundity of Bu. xylophilus. Furthermore, depletion of Mn-SOD decreased fecundity and virulence of Bu. xylophilus, while the insulin pathway is significantly affected. Thus, we propose that destructive pathogenicity of Bu. xylophilus to pines is partly owing to upregulated fecundity modulated by the insulin pathway in association with the ROS pathway and further enhanced by H2O2 oxidative stress. These findings provide a better understanding of pathogenic mechanisms in plant-pathogen interactions and adaptive evolution of invasive species. This article is part of the theme issue 'Biotic signalling sheds light on smart pest management'.


Assuntos
Expressão Gênica , Estresse Oxidativo/fisiologia , Doenças das Plantas/parasitologia , Tylenchida/fisiologia , Tylenchida/patogenicidade , Animais , China , Europa (Continente) , Árvores/parasitologia , Tylenchida/genética , Estados Unidos , Virulência/fisiologia
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