RESUMO
Human Dicer (hDicer) is a multi-domain protein belonging to the RNase III family. It plays pivotal roles in small RNA biogenesis during the RNA interference (RNAi) pathway by processing a diverse range of double-stranded RNA (dsRNA) precursors to generate â¼22 nt microRNA (miRNA) or small interfering RNA (siRNA) products for sequence-directed gene silencing. In this work, we solved the cryoelectron microscopy (cryo-EM) structure of hDicer in complex with its cofactor protein TRBP and revealed the precise spatial arrangement of hDicer's multiple domains. We further solved structures of the hDicer-TRBP complex bound with pre-let-7 RNA in two distinct conformations. In combination with biochemical analysis, these structures reveal a property of the hDicer-TRBP complex to promote the stability of pre-miRNA's stem duplex in a pre-dicing state. These results provide insights into the mechanism of RNA processing by hDicer and illustrate the regulatory role of hDicer's N-terminal helicase domain.
Assuntos
RNA Helicases DEAD-box/química , MicroRNAs/química , Ribonuclease III/química , Microscopia Crioeletrônica , RNA Helicases DEAD-box/genética , RNA Helicases DEAD-box/metabolismo , Ensaio de Desvio de Mobilidade Eletroforética , Humanos , MicroRNAs/metabolismo , Coativadores de Receptor Nuclear/química , Coativadores de Receptor Nuclear/genética , Coativadores de Receptor Nuclear/metabolismo , Conformação de Ácido Nucleico , Ligação Proteica , Domínios Proteicos , Estrutura Quaternária de Proteína , Clivagem do RNA , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/química , Proteínas Recombinantes/isolamento & purificação , Ribonuclease III/genética , Ribonuclease III/metabolismoRESUMO
Most short-lived eukaryotic proteins are degraded by the proteasome. A proteolytic core particle (CP) capped by regulatory particles (RPs) constitutes the 26S proteasome complex. RP biogenesis culminates with the joining of two large subcomplexes, the lid and base. In yeast and mammals, the lid appears to assemble completely before attaching to the base, but how this hierarchical assembly is enforced has remained unclear. Using biochemical reconstitutions, quantitative cross-linking/mass spectrometry, and electron microscopy, we resolve the mechanistic basis for the linkage between lid biogenesis and lid-base joining. Assimilation of the final lid subunit, Rpn12, triggers a large-scale conformational remodeling of the nascent lid that drives RP assembly, in part by relieving steric clash with the base. Surprisingly, this remodeling is triggered by a single Rpn12 α helix. Such assembly-coupled conformational switching is reminiscent of viral particle maturation and may represent a commonly used mechanism to enforce hierarchical assembly in multisubunit complexes.
Assuntos
Complexo de Endopeptidases do Proteassoma/química , Complexo de Endopeptidases do Proteassoma/metabolismo , Proteínas de Saccharomyces cerevisiae/química , Saccharomyces cerevisiae/química , Escherichia coli/metabolismo , Espectrometria de Massas , Microscopia Eletrônica , Modelos Moleculares , Estrutura Secundária de Proteína , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismoRESUMO
In oxygenic photosynthetic organisms, light energy is captured by antenna systems and transferred to photosystem II (PSII) and photosystem I (PSI) to drive photosynthesis1,2. The antenna systems of red algae consist of soluble phycobilisomes (PBSs) and transmembrane light-harvesting complexes (LHCs)3. Excitation energy transfer pathways from PBS to photosystems remain unclear owing to the lack of structural information. Here we present in situ structures of PBS-PSII-PSI-LHC megacomplexes from the red alga Porphyridium purpureum at near-atomic resolution using cryogenic electron tomography and in situ single-particle analysis4, providing interaction details between PBS, PSII and PSI. The structures reveal several unidentified and incomplete proteins and their roles in the assembly of the megacomplex, as well as a huge and sophisticated pigment network. This work provides a solid structural basis for unravelling the mechanisms of PBS-PSII-PSI-LHC megacomplex assembly, efficient energy transfer from PBS to the two photosystems, and regulation of energy distribution between PSII and PSI.
Assuntos
Complexos de Proteínas Captadores de Luz , Complexo de Proteína do Fotossistema I , Complexo de Proteína do Fotossistema II , Ficobilissomas , Porphyridium , Transferência de Energia , Complexos de Proteínas Captadores de Luz/química , Complexos de Proteínas Captadores de Luz/metabolismo , Complexos de Proteínas Captadores de Luz/ultraestrutura , Fotossíntese , Complexo de Proteína do Fotossistema I/química , Complexo de Proteína do Fotossistema I/metabolismo , Complexo de Proteína do Fotossistema I/ultraestrutura , Complexo de Proteína do Fotossistema II/química , Complexo de Proteína do Fotossistema II/metabolismo , Complexo de Proteína do Fotossistema II/ultraestrutura , Ficobilissomas/química , Ficobilissomas/metabolismo , Ficobilissomas/ultraestrutura , Porphyridium/química , Porphyridium/enzimologia , Porphyridium/metabolismo , Porphyridium/ultraestrutura , Microscopia Crioeletrônica , Imagem Individual de MoléculaRESUMO
Ageing and fertility are intertwined. Germline loss extends the lifespan in various organisms, termed gonadal longevity. However, the original longevity signal from the somatic gonad remains poorly understood. Here, we focused on the interaction between germline stem cells (GSCs) and their niche, the distal tip cells (DTCs), to explore the barely known longevity signal from the somatic gonad in C. elegans. We found that removing germline disrupts the cell adhesions between GSC and DTC, causing a significant transcriptomic change in DTC through hmp-2/ß-catenin and two GATA transcription factors, elt-3 and pqm-1 in this niche cell. Inhibiting elt-3 and pqm-1 in DTC suppresses gonadal longevity. Moreover, we further identified the TGF-ß ligand, tig-2, as the cytokine from DTC upon the loss of germline, which evokes the downstream gonadal longevity signalling throughout the body. Our findings thus reveal the source of the longevity signalling in response to germline removal, highlighting the stem cell niche as a critical signalling hub in ageing.
RESUMO
Many bacteria contain an ortholog of the Ro autoantigen, a ring-shaped protein that binds noncoding RNAs (ncRNAs) called Y RNAs. In the only studied bacterium, Deinococcus radiodurans, the Ro ortholog Rsr functions in heat-stress-induced ribosomal RNA (rRNA) maturation and starvation-induced rRNA decay. However, the mechanism by which this conserved protein and its associated ncRNAs act has been obscure. We report that Rsr and the exoribonuclease polynucleotide phosphorylase (PNPase) form an RNA degradation machine that is scaffolded by Y RNA. Single-particle electron microscopy, followed by docking of atomic models into the reconstruction, suggests that Rsr channels single-stranded RNA into the PNPase cavity. Biochemical assays reveal that Rsr and Y RNA adapt PNPase for effective degradation of structured RNAs. A Ro ortholog and ncRNA also associate with PNPase in Salmonella Typhimurium. Our studies identify another ribonucleoprotein machine and demonstrate that ncRNA, by tethering a protein cofactor, can alter the substrate specificity of an enzyme.
Assuntos
Deinococcus/química , Complexo Multienzimático de Ribonucleases do Exossomo/química , Estabilidade de RNA , RNA Bacteriano/química , RNA não Traduzido/metabolismo , Ribonucleoproteínas/metabolismo , Salmonella typhimurium/metabolismo , Animais , Sequência de Bases , Deinococcus/genética , Deinococcus/metabolismo , Complexo Multienzimático de Ribonucleases do Exossomo/metabolismo , Dados de Sequência Molecular , Polirribonucleotídeo Nucleotidiltransferase/química , Polirribonucleotídeo Nucleotidiltransferase/ultraestrutura , RNA Bacteriano/ultraestrutura , RNA não Traduzido/ultraestrutura , Ribonucleoproteínas/química , Ribonucleoproteínas/genética , Xenopus laevis/metabolismoRESUMO
Small interfering RNAs (siRNAs) are the key components for RNA interference (RNAi), a conserved RNA-silencing mechanism in many eukaryotes1,2. In Drosophila, an RNase III enzyme Dicer-2 (Dcr-2), aided by its cofactor Loquacious-PD (Loqs-PD), has an important role in generating 21 bp siRNA duplexes from long double-stranded RNAs (dsRNAs)3,4. ATP hydrolysis by the helicase domain of Dcr-2 is critical to the successful processing of a long dsRNA into consecutive siRNA duplexes5,6. Here we report the cryo-electron microscopy structures of Dcr-2-Loqs-PD in the apo state and in multiple states in which it is processing a 50 bp dsRNA substrate. The structures elucidated interactions between Dcr-2 and Loqs-PD, and substantial conformational changes of Dcr-2 during a dsRNA-processing cycle. The N-terminal helicase and domain of unknown function 283 (DUF283) domains undergo conformational changes after initial dsRNA binding, forming an ATP-binding pocket and a 5'-phosphate-binding pocket. The overall conformation of Dcr-2-Loqs-PD is relatively rigid during translocating along the dsRNA in the presence of ATP, whereas the interactions between the DUF283 and RIIIDb domains prevent non-specific cleavage during translocation by blocking the access of dsRNA to the RNase active centre. Additional ATP-dependent conformational changes are required to form an active dicing state and precisely cleave the dsRNA into a 21 bp siRNA duplex as confirmed by the structure in the post-dicing state. Collectively, this study revealed the molecular mechanism for the full cycle of ATP-dependent dsRNA processing by Dcr-2-Loqs-PD.
Assuntos
Microscopia Crioeletrônica , Proteínas de Drosophila , Drosophila melanogaster , RNA Helicases , RNA de Cadeia Dupla , RNA Interferente Pequeno , Proteínas de Ligação a RNA , Ribonuclease III , Trifosfato de Adenosina , Animais , Sítios de Ligação , Proteínas de Drosophila/química , Proteínas de Drosophila/metabolismo , Proteínas de Drosophila/ultraestrutura , Fosfatos/metabolismo , Conformação Proteica , RNA Helicases/química , RNA Helicases/metabolismo , RNA Helicases/ultraestrutura , RNA de Cadeia Dupla/química , RNA de Cadeia Dupla/metabolismo , RNA de Cadeia Dupla/ultraestrutura , RNA Interferente Pequeno/química , RNA Interferente Pequeno/metabolismo , RNA Interferente Pequeno/ultraestrutura , Proteínas de Ligação a RNA/química , Proteínas de Ligação a RNA/metabolismo , Proteínas de Ligação a RNA/ultraestrutura , Ribonuclease III/química , Ribonuclease III/metabolismo , Ribonuclease III/ultraestruturaRESUMO
A commencing and critical step in miRNA biogenesis involves processing of pri-miRNAs in the nucleus by Microprocessor. An important, but not completely understood, question is how Drosha, the catalytic subunit of Microprocessor, binds pri-miRNAs and correctly specifies cleavage sites. Here we report the cryoelectron microscopy structures of the Drosha-DGCR8 complex with and without a pri-miRNA. The RNA-bound structure provides direct visualization of the tertiary structure of pri-miRNA and shows that a helix hairpin in the extended PAZ domain and the mobile basic (MB) helix in the RNase IIIa domain of Drosha coordinate to recognize the single-stranded to double-stranded junction of RNA, whereas the dsRNA binding domain makes extensive contacts with the RNA stem. Furthermore, the RNA-free structure reveals an autoinhibitory conformation of the PAZ helix hairpin. These findings provide mechanistic insights into pri-miRNA cleavage site selection and conformational dynamics governing pri-miRNA recognition by the catalytic component of Microprocessor.
Assuntos
MicroRNAs/química , MicroRNAs/metabolismo , Ribonuclease III/química , Ribonuclease III/metabolismo , Animais , Microscopia Crioeletrônica , Humanos , Modelos Moleculares , Conformação Proteica , Domínios Proteicos , Proteínas de Ligação a RNA/química , Proteínas de Ligação a RNA/genética , Proteínas de Ligação a RNA/metabolismo , Ribonuclease III/genética , Spodoptera/citologiaRESUMO
Addressing interfacial effects during specimen preparation in cryogenic electron microscopy remains challenging. Here we introduce ESI-cryoPrep, a specimen preparation method based on electrospray ionization in native mass spectrometry, designed to alleviate issues associated with protein denaturation or preferred orientation induced by macromolecule adsorption at interfaces. Through fine-tuning spraying parameters, we optimized protein integrity preservation and achieved the desired ice thickness for analyzing target macromolecules. With ESI-cryoPrep, we prepared high-quality cryo-specimens of five proteins and obtained three-dimensional reconstructions at near-atomic resolution. Our findings demonstrate that ESI-cryoPrep effectively confines macromolecules within the middle of the thin layer of amorphous ice, facilitating the preparation of blotting-free vitreous samples. The protective mechanism, characterized by the uneven distribution of charged biomolecules of varying sizes within charged droplets, prevents the adsorption of target biomolecules at air-water or graphene-water interfaces, thereby avoiding structural damage to the protein particles or the introduction of dominant orientation issues.
Assuntos
Microscopia Crioeletrônica , Manejo de Espécimes , Espectrometria de Massas por Ionização por Electrospray , Microscopia Crioeletrônica/métodos , Manejo de Espécimes/métodos , Espectrometria de Massas por Ionização por Electrospray/métodos , Proteínas/química , Humanos , Substâncias Macromoleculares/químicaRESUMO
High-quality specimen preparation plays a crucial role in cryo-electron microscopy (cryo-EM) structural analysis. In this study, we have developed a reliable and convenient technique called the graphene sandwich method for preparing cryo-EM specimens. This method involves using two layers of graphene films that enclose macromolecules on both sides, allowing for an appropriate ice thickness for cryo-EM analysis. The graphene sandwich helps to mitigate beam-induced charging effect and reduce particle motion compared to specimens prepared using the traditional method with graphene support on only one side, therefore improving the cryo-EM data quality. These advancements may open new opportunities to expand the use of graphene in the field of biological electron microscopy.
Assuntos
Grafite , Microscopia Crioeletrônica , Confiabilidade dos Dados , Movimento (Física)RESUMO
Cryo-electron microscopy (cryo-EM) visualizes the atomic structure of macromolecules that are embedded in vitrified thin ice at their close-to-native state. However, the homogeneity of ice thickness, a key factor to ensure high image quality, is poorly controlled during specimen preparation and has become one of the main challenges for high-resolution cryo-EM. Here we found that the uniformity of thin ice relies on the surface flatness of the supporting film, and developed a method to use ultraflat graphene (UFG) as the support for cryo-EM specimen preparation to achieve better control of vitreous ice thickness. We show that the uniform thin ice on UFG improves the image quality of vitrified specimens. Using such a method we successfully determined the three-dimensional structures of hemoglobin (64 kDa), α-fetoprotein (67 kDa) with no symmetry, and streptavidin (52 kDa) at a resolution of 3.5 Å, 2.6 Å and 2.2 Å, respectively. Furthermore, our results demonstrate the potential of UFG for the fields of cryo-electron tomography and structure-based drug discovery.
Assuntos
Grafite , Microscopia Crioeletrônica/métodos , Grafite/química , Substâncias Macromoleculares , Tomografia com Microscopia EletrônicaRESUMO
Homeostasis and wound healing rely on stem cells (SCs) whose activity and directed migration are often governed by Wnt signaling. In dissecting how this pathway integrates with the necessary downstream cytoskeletal dynamics, we discovered that GSK3ß, a kinase inhibited by Wnt signaling, directly phosphorylates ACF7, a > 500 kDa microtubule-actin crosslinking protein abundant in hair follicle stem cells (HF-SCs). We map ACF7's GSK3ß sites to the microtubule-binding domain and show that phosphorylation uncouples ACF7 from microtubules. Phosphorylation-refractile ACF7 rescues overall microtubule architecture, but phosphorylation-constitutive mutants do not. Neither mutant rescues polarized movement, revealing that phospho-regulation must be dynamic. This circuitry is physiologically relevant and depends upon polarized GSK3ß inhibition at the migrating front of SCs/progeny streaming from HFs during wound repair. Moreover, only ACF7 and not GSKß-refractile-ACF7 restore polarized microtubule-growth and SC-migration to ACF7 null skin. Our findings provide insights into how this conserved spectraplakin integrates signaling, cytoskeletal dynamics, and polarized locomotion of somatic SCs.
Assuntos
Quinase 3 da Glicogênio Sintase/metabolismo , Proteínas dos Microfilamentos/metabolismo , Microtúbulos/metabolismo , Pele/metabolismo , Células-Tronco/metabolismo , Cicatrização , Animais , Movimento Celular , Células Cultivadas , Glicogênio Sintase Quinase 3 beta , Camundongos , Camundongos Transgênicos , Fosforilação , Estrutura Terciária de Proteína , Pele/citologia , Células-Tronco/citologiaRESUMO
Pangolins have been suggested as potential reservoir of zoonotic viruses, including SARS-CoV-2 causing the global COVID-19 outbreak. Here, we study the binding of two SARS-CoV-2-like viruses isolated from pangolins, GX/P2V/2017 and GD/1/2019, to human angiotensin-converting enzyme 2 (hACE2), the receptor of SARS-CoV-2. We find that the spike protein receptor-binding domain (RBD) of pangolin CoVs binds to hACE2 as efficiently as the SARS-CoV-2 RBD in vitro. Furthermore, incorporation of pangolin CoV RBDs allows entry of pseudotyped VSV particles into hACE2-expressing cells. A screen for binding of pangolin CoV RBDs to ACE2 orthologs from various species suggests a broader host range than that of SARS-CoV-2. Additionally, cryo-EM structures of GX/P2V/2017 and GD/1/2019 RBDs in complex with hACE2 show their molecular binding in modes similar to SARS-CoV-2 RBD. Introducing the Q498H substitution found in pangolin CoVs into the SARS-CoV-2 RBD expands its binding capacity to ACE2 homologs of mouse, rat, and European hedgehog. These findings suggest that these two pangolin CoVs may infect humans, highlighting the necessity of further surveillance of pangolin CoVs.
Assuntos
Enzima de Conversão de Angiotensina 2/metabolismo , Betacoronavirus/fisiologia , Pangolins/virologia , SARS-CoV-2/fisiologia , Glicoproteína da Espícula de Coronavírus/química , Glicoproteína da Espícula de Coronavírus/metabolismo , Substituição de Aminoácidos , Enzima de Conversão de Angiotensina 2/química , Animais , Sítios de Ligação , Células HEK293 , Ouriços/virologia , Especificidade de Hospedeiro , Humanos , Camundongos , Modelos Moleculares , Filogenia , Ligação Proteica , Conformação Proteica , Ratos , Glicoproteína da Espícula de Coronavírus/genética , Internalização do VírusRESUMO
BACKGROUND & AIMS: Because pancreatic cancer responds poorly to chemotherapy and immunotherapy, it is necessary to identify novel targets and compounds to overcome resistance to treatment. METHODS: This study analyzed genomic single nucleotide polymorphism sequencing, single-cell RNA sequencing, and spatial transcriptomics. Ehf-knockout mice, KPC (LSL-KrasG12D/+, LSL-Trp53R172H/+ and Pdx1-Cre) mice, CD45.1+ BALB/C nude mice, and CD34+ humanized mice were also used as subjects. Multiplexed immunohistochemistry and flow cytometry were performed to investigate the proportion of tumor-infiltrated C-X-C motif chemokine receptor 2 (CXCR2)+ neutrophils. In addition, multiplexed cytokines assays and chromatin immunoprecipitation assays were used to examine the mechanism. RESULTS: The TP53 mutation-mediated loss of tumoral EHF increased the recruitment of CXCR2+ neutrophils, modulated their spatial distribution, and further induced chemo- and immunotherapy resistance in clinical cohorts and preclinical syngeneic mice models. Mechanistically, EHF deficiency induced C-X-C motif chemokine ligand 1 (CXCL1) transcription to enhance in vitro and in vivo CXCR2+ neutrophils migration. Moreover, CXCL1 or CXCR2 blockade completely abolished the effect, indicating that EHF regulated CXCR2+ neutrophils migration in a CXCL1-CXCR2-dependent manner. The depletion of CXCR2+ neutrophils also blocked the in vivo effects of EHF deficiency on chemotherapy and immunotherapy resistance. The single-cell RNA-sequencing results of PDAC treated with Nifurtimox highlighted the therapeutic significance of Nifurtimox by elevating the expression of tumoral EHF and decreasing the weightage of CXCL1-CXCR2 pathway within the microenvironment. Importantly, by simultaneously inhibiting the JAK1/STAT1 pathway, it could significantly suppress the recruitment and function of CXCR2+ neutrophils, further sensitizing PDAC to chemotherapy and immunotherapies. CONCLUSIONS: The study demonstrated the role of EHF in the recruitment of CXCR2+ neutrophils and the promising role of Nifurtimox in sensitizing pancreatic cancer to chemotherapy and immunotherapy.
Assuntos
Quimiocina CXCL1 , Resistencia a Medicamentos Antineoplásicos , Infiltração de Neutrófilos , Neutrófilos , Neoplasias Pancreáticas , Receptores de Interleucina-8B , Animais , Neoplasias Pancreáticas/genética , Neoplasias Pancreáticas/tratamento farmacológico , Neoplasias Pancreáticas/imunologia , Neoplasias Pancreáticas/patologia , Neoplasias Pancreáticas/metabolismo , Receptores de Interleucina-8B/genética , Receptores de Interleucina-8B/metabolismo , Receptores de Interleucina-8B/antagonistas & inibidores , Humanos , Infiltração de Neutrófilos/efeitos dos fármacos , Resistencia a Medicamentos Antineoplásicos/genética , Neutrófilos/imunologia , Neutrófilos/metabolismo , Neutrófilos/efeitos dos fármacos , Camundongos , Quimiocina CXCL1/metabolismo , Quimiocina CXCL1/genética , Linhagem Celular Tumoral , Camundongos Knockout , Microambiente Tumoral , Imunoterapia/métodos , Camundongos Nus , Proteína Supressora de Tumor p53/metabolismo , Proteína Supressora de Tumor p53/genética , Camundongos Endogâmicos BALB C , Antineoplásicos/farmacologia , Transdução de Sinais , Mutação , Carcinoma Ductal Pancreático/genética , Carcinoma Ductal Pancreático/imunologia , Carcinoma Ductal Pancreático/tratamento farmacológico , Carcinoma Ductal Pancreático/patologiaRESUMO
Alternative ORFs (AltORFs) are unannotated sequences in genome that encode novel peptides or proteins named alternative proteins (AltProts). Although ribosome profiling and bioinformatics predict a large number of AltProts, mass spectrometry as the only direct way of identification is hampered by the short lengths and relative low abundance of AltProts. There is an urgent need for improvement of mass spectrometry methodologies for AltProt identification. Here, we report an approach based on size-exclusion chromatography for simultaneous enrichment and fractionation of AltProts from complex proteome. This method greatly simplifies the variance of AltProts discovery by enriching small proteins smaller than 40 kDa. In a systematic comparison between 10 methods, the approach we reported enabled the discovery of more AltProts with overall higher intensities, with less cost of time and effort compared to other workflows. We applied this approach to identify 89 novel AltProts from mouse liver, 39 of which were differentially expressed between embryonic and adult mice. During embryonic development, the upregulated AltProts were mainly involved in biological pathways on RNA splicing and processing, whereas the AltProts involved in metabolisms were more active in adult livers. Our study not only provides an effective approach for identifying AltProts but also novel AltProts that are potentially important in developmental biology.
Assuntos
Peptídeos , Proteômica , Animais , Camundongos , Proteômica/métodos , Peptídeos/metabolismo , Proteoma/metabolismo , Splicing de RNA , Fígado/metabolismoRESUMO
BACKGROUND: The significance of A-to-I RNA editing in nervous system development is widely recognized; however, its influence on retina development remains to be thoroughly understood. RESULTS: In this study, we performed RNA sequencing and ribosome profiling experiments on developing mouse retinas to characterize the temporal landscape of A-to-I editing. Our findings revealed temporal changes in A-to-I editing, with distinct editing patterns observed across different developmental stages. Further analysis showed the interplay between A-to-I editing and alternative splicing, with A-to-I editing influencing splicing efficiency and the quantity of splicing events. A-to-I editing held the potential to enhance translation diversity, but this came at the expense of reduced translational efficiency. When coupled with splicing, it could produce a coordinated effect on gene translation. CONCLUSIONS: Overall, this study presents a temporally resolved atlas of A-to-I editing, connecting its changes with the impact on alternative splicing and gene translation in retina development.
Assuntos
Biossíntese de Proteínas , Edição de RNA , Retina , Animais , Camundongos , Retina/metabolismo , Retina/embriologia , Processamento Alternativo , Inosina/metabolismo , Inosina/genética , Adenosina/metabolismoRESUMO
Carbon dots (CDs) are promising luminescent emission layer materials for next generation electroluminescent light emitting diodes (EL-LEDs) due to their many advantages, such as environmental friendliness, low cost, and high stability. However, limited by the spin-forbidden properties of the triplet transition, it is difficult to improve the external quantum efficiency (EQE) of fluorescent CDs-based EL-LEDs. Meanwhile, traditional thermally activated delayed fluorescent (TADF) CDs prepared using coating strategies are difficult to utilize in EL-LEDs due to the nonconductivity of the coating agent. Herein, we successfully developed matrix-free TADF CDs with yellow emission and achieved a device EQE of 5.68%, which is the highest value reported in CDs-based EL-LEDs. In addition, we also developed white EL-LEDs with an EQE of 1.70%. This study highlights the importance of interactions between precursors in modulating the electroluminescence properties of TADF emitters and provides an effective design principle for matrix-free TADF CDs.
RESUMO
Quasi-2D perovskites based blue light-emitting diodes (LEDs) suffer from its poor electroluminescence performance, mainly caused by the nonradiative recombination in in defect-rich low-n phases and the unbalanced hole-electron injection in the device. Here, we developed a highly efficient quasi-2D perovskite based sky-blue LEDs behaving recorded external quantum efficiency (EQE) of 21.07% by employing carbon dots (CDs) as additives in the hole transport layer (HTL). We ascribe the high EQE to the effective engineering of CDs: (1) The CDs at the interface of HTLs can suppress the formation of low-efficient n = 1 phase, resulting a high luminescence quantum yield and energy transfer efficiency of the mixed n-phase quasi-2D perovskites. (2) The CDs additives can reduce the conductivity of HTL, partially blocking the hole injection, and thus making more balanced hole-electron injection. The CDs-treated devices have excellent Spectral stability and enhanced operational stability and could be a new alternative additive in the perovskite optoelectronic devices.
RESUMO
Hyperbolic polaritons have been attracting increasing interest for applications in optoelectronics, biosensing, and super-resolution imaging. Here, we report the in-plane hyperbolic exciton polaritons in monolayer black-arsenic (B-As), where hyperbolicity arises strikingly from two exciton resonant peaks. Remarkably, the presence of two resonances at different momenta makes overall hyperbolicity highly tunable by strain, as the two exciton peaks can be merged into the same frequency to double the strength of hyperbolicity as well as light absorption under a 1.5% biaxial strain. Moreover, the frequency of the merged hyperbolicity can be further tuned from 1.35 to 0.8 eV by an anisotropic biaxial strain. Furthermore, electromagnetic numerical simulation reveals a strain-induced hyperbolicity, as manifested in a topological transition of iso-frequency contour of exciton polaritons. The good tunability, large exciton binding energy, and strong light absorption exhibited in the hyperbolic monolayer B-As make it highly suitable for nanophotonics applications under ambient conditions.
RESUMO
OBJECTIVE: The objective of this study is to improve the efficacy of CLDN18.2/CD3 bispecific T-cell engagers (BiTEs) as a promising immunotherapy against pancreatic ductal adenocarcinoma (PDAC). DESIGN: Humanised hCD34+/hCD3e+, Trp53R172HKrasG12DPdx1-Cre (KPC), pancreas-specific Cldn18.2 knockout (KO), fibroblast-specific Fcgr1 KO and patient-derived xenograft/organoid mouse models were constructed. Flow cytometry, Masson staining, Cell Titer Glo assay, virtual drug screening, molecular docking and chromatin immunoprecipitation were conducted. RESULTS: CLDN18.2 BiTEs effectively inhibited early tumour growth, but late-stage efficacy was significantly diminished. Mechanically, the Fc fragment of BiTEs interacted with CD64+ cancer-associated fibroblasts (CAFs) via activation of the SYK-VAV2-RhoA-ROCK-MLC2-MRTF-A-α-SMA/collagen-I pathway, which enhanced desmoplasia and limited late-stage infiltration of T cells. Molecular docking analysis found that vilanterol suppressed BiTEs-induced phosphorylation of VAV2 (Y172) in CD64+ CAFs and weakened desmoplasia. Additionally, decreased cyclic guanosine-adenosine monophosphate synthase/stimulator of interferon genes (STING) activity reduced proliferation of TCF-1+PD-1+ stem-like CD8+ T cells, which limited late-stage effects of BiTEs. Finally, vilanterol and the STING agonist synergistically boosted the efficacy of BiTEs by inhibiting the activation of CD64+ CAFs and enriching proliferation of stem-like CD8+ T cells, resulting in sustained anti-tumour activity. CONCLUSION: Vilanterol plus the STING agonist sensitised PDAC to CLDN18.2 BiTEs and augmented efficacy as a potential novel strategy.