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1.
Adv Mater ; : e2005900, 2021 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-33811422

RESUMO

Plasmonic core-shell nanostructures have attracted considerable attention in the scientific community recently due to their highly tunable optical properties. Plasmon-enhanced spectroscopies are one of the main applications of plasmonic nanomaterials. When excited by an incident laser of suitable wavelength, strong and highly localized electromagnetic (EM) fields are generated around plasmonic nanomaterials, which can significantly boost excitation and/or radiation processes that amplify Raman, fluorescence, or nonlinear signals and improve spectroscopic sensitivity. Herein, recent developments in plasmon-enhanced spectroscopies utilizing core-shell nanostructures are reviewed, including shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS), plasmon-enhanced fluorescence spectroscopy, and plasmon-enhanced nonlinear spectroscopy.

2.
Nanoscale ; 13(12): 5935-5936, 2021 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-33734271
3.
Artigo em Inglês | MEDLINE | ID: mdl-33523581

RESUMO

Developing advanced characterization techniques for single-atom catalysts (SACs) is of great significance to identify their structural and catalytic properties. Raman spectroscopy can provide molecular structure information, and thus, the technique is a promising tool for catalysis. However, its application in SACs remains a great challenge because of its low sensitivity. We develop a highly sensitive strategy that achieves the characterization of the structure of SACs and in situ monitoring of the catalytic reaction processes on them by shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) for the first time. Using the strategy, Pd SACs on different supports were identified by Raman spectroscopy and the nucleation process of Pd species from single atoms to nanoparticles was revealed. Moreover, the catalytic reaction processes of the hydrogenation of nitro compounds on Pd SACs were monitored in situ, and molecular insights were obtained to uncover the unique catalytic properties of SACs. This work provides a new spectroscopic tool for the in situ study of SACs, especially at solid-liquid interfaces.

4.
Plant Cell ; 2021 Feb 02.
Artigo em Inglês | MEDLINE | ID: mdl-33619522

RESUMO

Arabidopsis CDG1 negatively regulates flg22- and chitin-triggered immunity by promoting FLS2 and CERK1 degradation and is partially required for bacterial effector AvrRpm1-induced RIN4 phosphorylation. Negative regulators play indispensable roles in pattern-triggered immunity in plants by preventing sustained immunity impeding growth. Here, we report Arabidopsis thaliana CONSTITUTIVE DIFFERENTIAL GROWTH1 (CDG1), a receptor-like cytoplasmic kinase VII member, as a negative regulator of bacterial flagellin/flg22- and fungal chitin-triggered immunity. CDG1 can interact with the flg22 receptor FLAGELLIN SENSITIVE2 (FLS2) and chitin co-receptor CHITIN ELICITOR RECEPTOR KINASE1 (CERK1). CDG1 overexpression impairs flg22 and chitin responses by promoting the degradation of FLS2 and CERK1. This process requires the kinase activity of MEK KINASE1 (MEKK1), but not the Plant U-Box (PUB) ubiquitin E3 ligases PUB12 and PUB13. Interestingly, the Pseudomonas syringae effector AvrRpm1 can induce CDG1 to interact with its host target RPM1-INTERACTING PROTEIN4 (RIN4), which depends on the ADP-ribosyl transferase activity of AvrRpm1. CDG1 is capable of phosphorylating RIN4 in vitro at multiple sites including Thr166 and the AvrRpm1-induced Thr166 phosphorylation of RIN4 is diminished in cdg1 null plants. Accordingly, CDG1 knockout attenuates AvrRpm1-induced hypersensitive response and increases the growth of AvrRpm1-secreting bacteria in plants. Unexpectedly, AvrRpm1 can also induce FLS2 depletion, which is fully dependent on RIN4 and partially dependent on CDG1, but does not require the kinase activity of MEKK1. Collectively, this study reveals previously unknown functions of CDG1 in both pattern-triggered immunity and effector-triggered susceptibility in plants.

5.
Artigo em Inglês | MEDLINE | ID: mdl-33587592

RESUMO

Fabricating single-molecule junctions with asymmetric metal electrodes is significant for realizing single-molecule diodes, but it remains a big challenge. Herein, we develop a z-piezo pulse-modulated scanning tunneling microscopy break junction (STM-BJ) technique to construct a robust asymmetric junction with different metal electrodes. The asymmetric Ag/BPY-EE/Au single-molecule junctions exhibit a middle conductance value in between those of the two individual symmetric metal electrode junctions, which is consistent with the order of calculated energy-dependent transmission coefficient T(E) of the asymmetric junctions at EF. Furthermore, the single-molecule conductance of Ag/BPY-EE/Au decreases by about 70% when reversing the bias voltage from 100 to -100 mV, and a clear asymmetric I-V feature at the single-molecule level is observed for these junctions. This rectifying behavior could be ascribed to a different interfacial coupling of molecules at the two end electrodes, which is confirmed by the different displacement of T(E) at the two bias voltages. Other asymmetric junctions exhibit similar rectifying behavior. The current work provides a feasible way to fabricate hybrid junctions based on asymmetric metal electrodes and investigate their electron transport toward the design of molecular rectifiers.

6.
J Am Chem Soc ; 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33449677

RESUMO

PtNi alloy catalysts have excellent catalytic activity and are considered some of the most promising electrocatalysts capable of replacing pure Pt for the oxygen reduction reaction (ORR). For PtNi alloys, Ni-doping can improve performance by changing the electronic and structural properties of the catalyst surface and its interaction with reaction intermediates. However, to date there is no direct spectral evidence detecting or identifying the effect of Ni on the ORR in PtNi alloy catalysts. Herein, we introduce a surface-enhanced Raman spectroscopic (SERS) "borrowing" strategy for investigating ORR processes catalyzed by Au@PtNi nanoparticles (NPs). The bond vibration of adsorbed peroxide intermediate species (*OOH) was obtained, and the effect of Ni on the interaction between surface Pt and *OOH was studied by varying the Ni content in the alloy. The frequency of the *OOH spectral band has an obvious red-shift with increasing Ni content. Combined with density functional theory (DFT) calculations, we show that Ni-doping can optimize *OOH surface binding on the Pt surface, achieving more efficient electron transfer, thus improving the ORR rate. Notably, these results evidence the SERS borrowing strategy as an effective technique for in situ observations of catalytic processes.

7.
Annu Rev Phys Chem ; 2021 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-33472380

RESUMO

As energy demands increase, electrocatalysis serves as a vital tool in energy conversion. Elucidating electrocatalytic mechanisms using in situ spectroscopic characterization techniques can provide experimental guidance for preparing high-efficiency electrocatalysts. Surface-enhanced Raman spectroscopy (SERS) can provide rich spectral information for ultratrace surface species and is extremely well suited to studying their activity. To improve the material and morphological universalities, researchers have employed different kinds of nanostructures that have played important roles in the development of SERS technologies. Different strategies, such as so-called borrowing enhancement from shell-isolated modes and shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS)-satellite structures, have been proposed to obtain highly effective Raman enhancement, and these methods make it possible to apply SERS to various electrocatalytic systems. Here, we discuss the development of SERS technology, focusing on its applications in different electrocatalytic reactions (such as oxygen reduction reactions) and at different nanostructure surfaces, and give a brief outlook on its development. Expected final online publication date for the Annual Review of Physical Chemistry, Volume 72 is April 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

8.
Plant J ; 2021 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-33506579

RESUMO

Lysin motif (LysM) is a carbohydrate-binding module often found in secreted or transmembrane proteins in living organisms from prokaryotes to eukaryotes. Thus far, all characterized LysM-containing proteins in plants are plasma membrane-resident receptors or co-receptors playing roles in plant-microbe interactions. Here, we interrogate the Arabidopsis LysM/F-box-containing protein InLYP1 and reveal its function in glycine metabolism. InLYP1 was mainly expressed by vigorously growing tissues, encoding a nuclear-cytoplasmic protein. We validated InLYP1 as part of the SKP1-CULLIN1-F-box E3 complex for mediating protein degradation. The glycine decarboxylase P-protein 1 (GLDP1) was identified as an InLYP1-interacting protein by both immunoprecipitation/mass spectrometry and yeast two-hybrid library screening. InLYP1 could also interact with GLDP2, a paralog of GLDP1 with weaker catalytic activity, and could mediate the degradation of GLDP2 but not GLDP1. Interestingly, both GLDPs could be O-glycosylated and form homodimers or heterodimers. Overexpression of InLYP1L9A encoding a dominant-negative variant could cause seedling germination retardation on the medium containing glycine. Collectively, these results shed light on the function of plant intracellular LysM-containing proteins, and suggest that InLYP1 may deplete GLDP2 to facilitate glycine decarboxylation in Arabidopsis.

9.
ACS Appl Mater Interfaces ; 13(1): 1766-1772, 2021 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-33373202

RESUMO

The assemblies of plasmonic nanoparticles (NPs) are the universal methods for enhancing their surface-enhanced Raman scattering (SERS) activities. However, the present methods suffer from the problems of poor reproducibility, complicated fabrication, or the adsorption of ligands on the surface, which limit their practical applications. In this work, by using a facile freeze-thaw method, we are able to fabricate the assemblies of Ag NPs with highly reproducible SERS activity without the use of ligands. Moreover, the Ag NPs can be well kept in a frozen state for a long time with few influences on the reproducibility (relative standard deviation, RSD ca. 7%), while those kept in colloid (4 °C) suffer from gradual surface oxidation and aggregation. Such a simple freeze-thaw method does not require the introduction of any ligands (or linkers) with long-term stability and reproducibility, implying its wide applications in practical SERS sensing.


Assuntos
Antibacterianos/análise , Nanopartículas Metálicas/química , Ofloxacino/análise , Prata/química , Poluentes Químicos da Água/análise , Pesqueiros , Congelamento , Limite de Detecção , Reprodutibilidade dos Testes , Análise Espectral Raman
10.
Artigo em Inglês | MEDLINE | ID: mdl-33325603

RESUMO

Elucidating hydrogen oxidation reaction (HOR) mechanisms in alkaline conditions is vital for understanding and improving the efficiency of anion-exchange-membrane fuel cells. However, uncertainty remains around the alkaline HOR mechanism owing to a lack of direct in situ evidence of intermediates. In this study, in situ electrochemical surface-enhanced Raman spectroscopy (SERS) and DFT were used to study HOR processes on PtNi alloy and Pt surfaces, respectively. Spectroscopic evidence indicates that adsorbed hydroxy species (OHad ) were directly involved in HOR processes in alkaline conditions on the PtNi alloy surface. However, OHad species were not observed on the Pt surface during the HOR. We show that Ni doping promoted hydroxy adsorption on the platinum-alloy catalytic surface, improving the HOR activity. DFT calculations also suggest that the free energy was decreased by hydroxy adsorption. Consequently, tuning OH adsorption by designing bifunctional catalysts is an efficient method for promoting HOR activity.

11.
Front Psychiatry ; 11: 549148, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33250790

RESUMO

Objective: Poor mental health is associated with impaired social functioning, lower quality of life, and increased risk of suicide and mortality. This study examined the prevalence of poor general mental health among older adults (aged 65 years and above) and its sociodemographic correlates in Hebei province, which is a predominantly agricultural area of China. Methods: This epidemiological survey was conducted from April to August 2016. General mental health status was assessed using the 12-item General Health Questionnaire (GHQ-12). Results: A total of 3,911 participants were included. The prevalence of poor mental health (defined as GHQ-12 total score ≥ 4) was 9.31% [95% confidence interval (CI): 8.4-10.2%]. Multivariable logistic regression analyses found that female gender [P < 0.001, odds ratio (OR) = 1.63, 95% CI: 1.29-2.07], lower education level (P = 0.048, OR = 1.33, 95% CI: 1.00-1.75), lower annual household income (P = 0.005, OR = 1.72, 95% CI: 1.17-2.51), presence of major medical conditions (P < 0.001, OR = 2.95, 95% CI: 2.19-3.96) and family history of psychiatric disorders (P < 0.001, OR = 3.53, 95% CI: 2.02-6.17) were significantly associated with poor mental health. Conclusion: The prevalence of poor mental health among older adults in a predominantly agricultural area was lower than findings from many other countries and areas in China. However, continued surveillance of mental health status among older adults in China is still needed.

12.
J Integr Plant Biol ; 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-33058471

RESUMO

Synthetic gene activators consisting of nuclease-dead Cas9 (dCas9) for single-guide RNA (sgRNA)-directed promoter binding and a transcriptional activation domain (TAD) represent new tools for gene activation from endogenous genomic locus in basic and applied plant research. However, multiplex gene co-activation by dCas9-TADs has not been demonstrated in whole plants. There is also room to optimize the performance of these tools. Here, we report that our previously developed gene activator, dCas9-TV, could simultaneously upregulate OsGW7 and OsER1 in rice by up to 3,738 fold, with one sgRNA targeting to each promoter. The gene co-activation could persist to at least the fourth generation. Astonishingly, the polycistronic tRNA-sgRNA expression under the maize ubiquitin promoter, a Pol II promoter, could cause enormous activation of these genes by up to >40,000 fold in rice. Moreover, the yeast GCN4 coiled coil-mediated dCas9-TV dimerization appeared to be promising for enhancing gene activation. Finally, we successfully introduced a self-amplification loop for dCas9-TV expression in Arabidopsis to promote the transcriptional upregulation of AtFLS2, a previously characterized dCas9-TV-refractory gene with considerable basal expression. Collectively, this work illustrates the robustness of dCas9-TV in multigene co-activation and provides broadly useful strategies for boosting transcriptional activation efficacy of dCas9-TADs in plants. This article is protected by copyright. All rights reserved.

13.
Artigo em Inglês | MEDLINE | ID: mdl-32918778

RESUMO

The adsorption and electrooxidation of CO molecules at well-defined Pt(hkl) single-crystal electrode surfaces is a key step towards addressing catalyst poisoning mechanisms in fuel cells. Herein, we employed in situ electrochemical shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) coupled with theoretical calculation to investigate CO electrooxidation on Pt(hkl) surfaces in acidic solution. We obtained the Raman signal of top- and bridge-site adsorbed CO* molecules on Pt(111) and Pt(100). In contrast, on Pt(110) surfaces only top-site adsorbed CO* was detected during the entire electrooxidation process. Direct spectroscopic evidence for OH* and COOH* species forming on Pt(100) and Pt(111) surfaces was afforded and confirmed subsequently via isotope substitution experiments and DFT calculations. In summary, the formation and adsorption of OH* and COOH* species plays a vital role in expediting the electrooxidation process, which relates with the pre-oxidation peak of CO electrooxidation. This work deepens knowledge of the CO electrooxidation process and provides new perspectives for the design of anti-poisoning and highly effective catalysts.

14.
Food Funct ; 11(8): 7245-7254, 2020 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-32766662

RESUMO

Antibacterial peptide CM4 (ABP-CM4) is a small cationic peptide with broad-spectrum activities against bacteria, fungi and tumor cells and may possibly be used as an antimicrobial agent. In this study, a C-terminal amidated antibacterial peptide ABP-CM4 (ABP-CM4N) with the strongest antibacterial activity was obtained through screening the antibacterial activities of ABP-CM4 with different modifications. The minimal inhibitory concentration of ABP-CM4N was 8 µM against P. aeruginosa (ATCC 27853) which was lower than that of ABP-CM4 (16 µM). The strengthened antimicrobial activity of ABP-CM4N may be associated with the increased membrane binding capacity, being two times that of ABP-CM4 (p < 0.001). The antibacterial mechanism of ABP-CM4N to Pseudomonas aeruginosa was examined by means of cell membrane integrity analysiss, the intracellular ultrastructure change observation and E. coli genomic DNA binding assay. It was found that ABP-CM4N had the same antimicrobial mechanism as ABP-CM4, and the aim of the antimicrobial mechanism was mainly to destroy the cell membrane which caused nucleic acid or protein leakage, and secondly to interact with E. coli genomic DNA after penetrating the cell membrane. Furthermore, in vitro ABP-CM4N showed a better bacteriostatic activity in meats, with the treated samples showing two to three times less positive colonies than ABP-CM4.

15.
Nat Nanotechnol ; 15(11): 922-926, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32778804

RESUMO

The progress of plasmon-based technologies relies on an understanding of the properties of the enhanced electromagnetic fields generated by the coupling nanostrucutres1-6. Plasmon-enhanced applications include advanced spectroscopies7-10, optomechanics11, optomagnetics12 and biosensing13-17. However, precise determination of plasmon field intensity distribution within a nanogap remains challenging. Here, we demonstrate a molecular ruler made from a set of viologen-based, self-assembly monolayers with which we precisely measures field distribution within a plasmon nanocavity with ~2-Å spatial resolution. We observed an unusually large plasmon field intensity inhomogeneity that we attribute to the formation of a plasmonic comb in the nanocavity. As a consequence, we posit that the generally adopted continuous media approximation for molecular monolayers should be used carefully.

16.
Life Sci Alliance ; 3(10)2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32788227

RESUMO

Quorum sensing (QS) is a recognized phenomenon that is crucial for regulating population-related behaviors in bacteria. However, the direct specific effect of QS molecules on host biology is largely understudied. In this work, we show that the QS molecule DSF (cis-11-methyl-dodecenoic acid) produced by Xanthomonas campestris pv. campestris can suppress pathogen-associated molecular pattern-triggered immunity (PTI) in Arabidopsis thaliana, mediated by flagellin-induced activation of flagellin receptor FLS2. The DSF-mediated attenuation of innate immunity results from the alteration of FLS2 nanoclusters and endocytic internalization of plasma membrane FLS2. DSF altered the lipid profile of Arabidopsis, with a particular increase in the phytosterol species, which impairs the general endocytosis pathway mediated by clathrin and FLS2 nano-clustering on the plasma membrane. The DSF effect on receptor dynamics and host immune responses could be entirely reversed by sterol removal. Together, our results highlighted the importance of sterol homeostasis to plasma membrane organization and demonstrate a novel mechanism by which pathogenic bacteria use their communicating molecule to manipulate pathogen-associated molecular pattern-triggered host immunity.

17.
Phys Rev Lett ; 125(4): 047401, 2020 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-32794816

RESUMO

Sum-frequency generation (SFG) spectroscopy is a highly versatile tool for surface analysis. Improving the SFG intensity per molecule is important for observing low concentrations of surface species and intermediates in dynamic systems. Herein, Shell-Isolated-Nanoparticle-Enhanced SFG (SHINE-SFG) was used to probe a model substrate. The model substrate, p-mercaptobenzonitrile adsorbed on a Au film with SHINs deposited on top, provided an enhancement factor of up to 10^{5}. Through wavelength- and polarization-dependent SHINE-SFG spectroscopy, the majority of the signal enhancement was found to come from both plasmon enhanced emission and chemical enhancement mechanisms. A new enhancement regime, i.e., the nonlinear coupling of SHINE-SFG with difference frequency generation, was also identified. This novel mechanism provides insight into the enhancement of nonlinear coherent spectroscopies and a possible strategy for the rational design of enhancing substrates utilizing coupling processes.

18.
Plant Cell ; 32(10): 3290-3310, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32753431

RESUMO

In plants, the ubiquitin-proteasome system, endosomal sorting, and autophagy are essential for protein degradation; however, their interplay remains poorly understood. Here, we show that four Arabidopsis (Arabidopsis thaliana) E3 ubiquitin ligases, SEVEN IN ABSENTIA OF ARABIDOPSIS THALIANA1 (SINAT1), SINAT2, SINAT3, and SINAT4, regulate the stabilities of FYVE DOMAIN PROTEIN REQUIRED FOR ENDOSOMAL SORTING1 (FREE1) and VACUOLAR PROTEIN SORTING23A (VPS23A), key components of the endosomal sorting complex required for transport-I, to modulate abscisic acid (ABA) signaling. GFP-SINAT1, GFP-SINAT2, and GFP-SINAT4 primarily localized to the endosomal and autophagic vesicles. SINATs controlled FREE1 and VPS23A ubiquitination and proteasomal degradation. SINAT overexpressors showed increased ABA sensitivity, ABA-responsive gene expression, and PYRABACTIN RESISTANCE1-LIKE4 protein levels. Furthermore, the SINAT-FREE1/VPS23A proteins were codegraded by the vacuolar pathway. In particular, during recovery post-ABA exposure, SINATs formed homo- and hetero-oligomers in vivo, which were disrupted by the autophagy machinery. Taken together, our findings reveal a novel mechanism by which the proteasomal and vacuolar turnover systems regulate ABA signaling in plants.

19.
Appl Spectrosc ; 74(11): 1365-1373, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32748642

RESUMO

Many foodstuffs are extremely susceptible to contamination with aflatoxins, in which aflatoxin B1 is highly toxic and carcinogenic. Therefore, it is crucial to develop a rapid and effective analytical method for detecting and monitoring aflatoxin B1 in food. Herein, a surface-enhanced Raman spectroscopic (SERS) method combined with QuEChERS (quick, easy, cheap-effective, rugged, safe) sample pretreatment technique was used to detect aflatoxin B1. Sample preparation was optimized into a one-step extraction method using an Au nanoparticle-based solution (Au sol) as the SERS detection substrate. An affordable portable Raman spectrometer was then used for rapid, label-free, quantitative detection of aflatoxin B1 levels in foodstuffs. This method showed a good linear log relationship between the Raman signal intensity of aflatoxin B1 in the 1-1000 µg L-1 concentration range with a limit of detection of 0.85 µg kg-1 and a correlation coefficient of 0.9836. Rapid aflatoxin B1 detection times of ∼10 min for wheat, corn, and protein feed powder samples were also achieved. This method has high sensitivity, strong specificity, excellent stability, is simple to use, economical, and is suitable for on-site detection, with good prospects for practical application in the field of food safety.

20.
Sci Rep ; 10(1): 12266, 2020 07 23.
Artigo em Inglês | MEDLINE | ID: mdl-32703962

RESUMO

Poor sleep quality is associated with negative health outcomes and high treatment burden. This study investigated the prevalence of poor sleep quality and its socio-demographic correlates among older adults in Hebei province, which is a predominantly agricultural region of China. A large-scale cross-sectional epidemiological survey was conducted from April to August 2016. The study used a multistage, stratified, cluster random sampling method. Sleep quality was assessed by the Pittsburgh Sleep Quality Index (PSQI). A total of 3,911 participants were included. The prevalence of poor sleep quality (defined as PSQI > 7) was 21.0% (95% CI 19.7-22.2%), with 22.3% (95% CI 20.9-23.8%) in rural areas and 15.9% (95% CI 13.4-18.4%) in urban areas. Multivariable logistic regression analyses found that female gender (P < 0.001, OR 2.4, 95% CI 2.00-2.82), rural areas (P = 0.002, OR 1.5, 95% CI 1.14-1.86), presence of major medical conditions (P < 0.001, OR 2.4, 95% CI 2.02-2.96) and family history of psychiatric disorders (P < 0.001, OR 2.7, 95% CI 1.60-4.39) were independently associated with higher risk of poor sleep quality. Poor sleep quality was common among older adults in Hebei province of China. Regular assessment of sleep quality and accessible sleep treatments for older population should be provided in agricultural areas of China.

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