Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 91
Filtrar
1.
Cell Mol Life Sci ; 81(1): 273, 2024 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-38900294

RESUMO

Long-term memory formation requires de novo RNA and protein synthesis. Using differential display PCR, we found that the NCoR1 cDNA fragment is differentially expressed between fast learners and slow learners, with fast learners showing a lower expression level than slow learners in the water maze learning task. Fast learners also show lower NCoR1 mRNA and protein expression levels. In addition, spatial training decreases both NCoR1 mRNA and protein expression, whereas NCoR1 conditional knockout (cKO) mice show enhanced spatial memory. In studying the molecular mechanism, we found that spatial training decreases the association between NCoR1 and DEC2. Both NCoR1 and DEC2 suppress the expression of BDNF, integrin α3 and SGK1 through C/EBPα binding to their DNA promoters, but overexpression of DEC2 in NCoR1 cKO mice rescues the decreased expression of these proteins compared with NCoR1 loxP mice overexpressing DEC2. Further, spatial training decreases DEC2 expression. Spatial training also enhances C/EBPα binding to Bdnf, Itga3 and Sgk1 promoters, an effect also observed in fast learners, and both NCoR1 and DEC2 control C/EBPα activity. Whereas knockdown of BDNF, integrin α3 or SGK1 expression impairs spatial learning and memory, it does not affect Y-maze performance, suggesting that BDNF, integrin α3 and SGK1 are involved in long-term memory formation, but not short-term memory formation. Moreover, NCoR1 expression is regulated by the JNK/c-Jun signaling pathway. Collectively, our findings identify DEC2 as a novel interacting protein of NCoR1 and elucidate the novel roles and mechanisms of NCoR1 and DEC2 in negative regulation of spatial memory formation.


Assuntos
Aprendizagem em Labirinto , Camundongos Knockout , Correpressor 1 de Receptor Nuclear , Memória Espacial , Animais , Memória Espacial/fisiologia , Camundongos , Correpressor 1 de Receptor Nuclear/metabolismo , Correpressor 1 de Receptor Nuclear/genética , Aprendizagem em Labirinto/fisiologia , Masculino , Camundongos Endogâmicos C57BL , Regiões Promotoras Genéticas , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Proteínas Serina-Treonina Quinases , Proteínas Imediatamente Precoces
2.
Opt Express ; 32(6): 9405-9419, 2024 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-38571176

RESUMO

In this paper, we present the design, optimization, and implementation of a sub-wavelength grating (SWG) multi-mode interference coupler (MMI) on the silicon nitride photonic integrated circuit (PIC) platform with a significantly enhanced bandwidth compared to the conventional MMI. We extend the SWG MMI theory, previously presented for the silicon-on-insulator platform, to the Si3N4/SiO2 platform. Our approach involves an initial parameter optimization for a non-paired design, followed by a shift to a paired design that offers a smaller footprint and a broader bandwidth. The optimized SWG MMI exhibits a 1 dB bandwidth of 300 nm for both the insertion loss and power imbalance, making it a significant addition to silicon nitride photonics.

3.
Nano Lett ; 23(24): 11614-11620, 2023 Dec 27.
Artigo em Inglês | MEDLINE | ID: mdl-37937950

RESUMO

An analysis of the optical response of a GaN-based metalens was conducted alongside the utilization of two sequential artificial intelligence (AI) models in addressing the occasional issues of blurriness and color cast in captured images. The optical loss of the metalens in the blue spectral range was found to have resulted in the color cast of images. Autoencoder and CodeFormer sequential models were employed in order to correct the color cast and reconstruct image details, respectively. Said sequential models successfully addressed the color cast and reconstructed details for all of the allocated face image categories. Subsequently, the CIE 1931 chromaticity diagrams and peak signal-to-noise ratio analysis provided numerical evidence of the AI models' effectiveness in image reconstruction. Furthermore, the AI models can still repair the image without blue information. Overall, the integration of metalens and artificial intelligence models marks a breakthrough in enhancing the performance of full-color metalens-based imaging systems.

4.
Opt Express ; 31(4): 6389-6400, 2023 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-36823896

RESUMO

To provide a solution to the issue of the non-flat focal surface in traditional Rowland AWGs, we have designed and implemented a Si3N4 three-stigmatic-point arrayed waveguide grating (TSP AWG) with three inputs, and a spectral resolving power over 17,000 has been achieved experimentally. The flat focal surface of this AWG can accommodate a butt-coupled detector array positioned at the output facet without any reduction of the resolving power of the edge channels. Therefore, it is particularly advantageous to some astronomical applications which require an AWG as a light-dispersing component to obtain a complete 2D spectrum. As a proof-of-concept for next generation devices, the multi-input aspect of the design accommodates multiple single-mode fibers coming into the AWG. In addition, because the device is implemented on a high-index-contrast platform (Si3N4/SiO2), a compact size of ∼9.3 × 9.3 mm2 is achieved.

5.
Sensors (Basel) ; 23(17)2023 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-37687994

RESUMO

The steel rail and wheel in the railway system offer a high precision and smooth-running surface. Nevertheless, the point of contact between the rail and wheel presents a critical area that can give rise to rail corrugation. This phenomenon can potentially elevate sound and vibration levels in the vicinity considerably, necessitating advanced monitoring and assessment measures. Recently, many efforts have been directed towards utilizing in-service trains for evaluating rail corrugation, and the evaluation has primarily relied on axle-box acceleration (ABA). However, the ABA measurements require a higher threshold for vibration detection. This study introduces a novel approach to rail corrugation detection by carriage floor acceleration (CFA), aimed at lowering the detection threshold. The method capitalizes on the acceleration data sensed on the carriage floor, which is induced by the sound pressure (e.g., sound-field excitation) generated at the wheel-rail contact point. An exploration of the correlation between these datasets is undertaken by simultaneously measuring both ABA and CFA. Moreover, a pivotal aspect of this research is the development of the eigenfrequency rail corrugation index (E-RCI), a mechanism that culminates energy around specific eigenfrequencies by CFA. Through this index, a focused analysis of rail corrugation patterns is facilitated. The study further delves into the stability, repeatability, and sensitivity of the E-RCI via varied measurement scenarios. Ultimately, the CFA-based rail corrugation identification is verified, establishing its practical applicability and offering a distinct approach to detecting and characterizing rail corrugation phenomena. This study has introduced an innovative methodology for rail corrugation detection using CFA, with the principal objective of lowering the detection threshold. This approach offers an efficient measurement technique for identifying rail corrugation areas, thereby potentially reducing maintenance costs and enhancing efficiency within the railway industry.

6.
Mol Ther ; 29(1): 376-395, 2021 01 06.
Artigo em Inglês | MEDLINE | ID: mdl-32950104

RESUMO

The amyloid precursor protein (APP) intracellular domain (AICD) is implicated in the pathogenesis of Alzheimer's disease (AD), but post-translational modification of AICD has rarely been studied and its role in AD is unknown. In this study, we examined the role and molecular mechanism of AICD SUMOylation in the pathogenesis of AD. We found that AICD is SUMO-modified by the SUMO E3 ligase protein inhibitor of activated STAT1 (PIAS1) in the hippocampus at Lys-43 predominantly, and that knockdown of PIAS1 decreases endogenous AICD SUMOylation. AICD SUMOylation increases AICD association with its binding protein Fe65 and increases AICD nuclear translocation. Furthermore, AICD SUMOylation increases AICD association with cyclic AMP-responsive element binding protein (CREB) and p65 and their DNA binding for transcriptional activation of neprilysin (NEP) and transthyretin (TTR), two major Aß-degrading enzymes, respectively. Consequently, AICD SUMOylation decreases the Aß level, Aß oligomerization, and amyloid plaque deposits. It also rescues spatial memory deficits in APP/PS1 mice. Conversely, blockade of AICD SUMOylation at Lys-43 produces the opposite effects. Melatonin is identified as an endogenous stimulus that induces AICD SUMOylation. It also decreases the Aß level and rescues reduction of PIAS1, NEP, and TTR expression in APP/PS1 mice. In this study, we demonstrate that AICD SUMOylation functions as a novel endogenous defense mechanism to combat AD.


Assuntos
Doença de Alzheimer/genética , Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/genética , Peptídeos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/metabolismo , Melatonina/metabolismo , Ativação Transcricional , Doença de Alzheimer/patologia , Animais , Proteína de Ligação a CREB/metabolismo , Modelos Animais de Doenças , Melatonina/farmacologia , Camundongos , Ligação Proteica , Proteínas Inibidoras de STAT Ativados/genética , Proteínas Inibidoras de STAT Ativados/metabolismo , Proteólise/efeitos dos fármacos , Sumoilação/efeitos dos fármacos , Ativação Transcricional/efeitos dos fármacos
7.
Electrophoresis ; 42(21-22): 2206-2214, 2021 11.
Artigo em Inglês | MEDLINE | ID: mdl-34472124

RESUMO

Resistive pulse sensing using solid-state nanopores provides a unique platform for detecting the structure and concentration of molecules of different types of analytes in an electrolyte solution. The capture of an entity into a nanopore is subject not only to the electrostatic force but also the effect of electroosmotic flow originating from the charged nanopore surface. In this study, we theoretically analyze spherical particle electrophoretic behavior near the entrance of a charged nanopore. By investigating the effects of pore size, particle-pore distance, and salt concentration on particle velocity, we summarize dominant mechanisms governing particle behavior for a range of conditions. In the literature, the Helmholtz-Smoluchowski equation is often adopted to evaluate particle translocation by considering the zeta potential difference between the particle and nanopore surfaces. We point out that, due to the difference of the electric field inside and outside the nanopore and the influence from the existence of the particle itself, the zeta potential of the particle, however, needs to be at least 30% higher than that of the nanopore to allow the particle to enter into the nanopore when its velocity is close to zero. Accordingly, we summarize the effective salt concentrations that enable successful particle capture and detection for different pore sizes, offering direct guidance for nanopore applications.


Assuntos
Eletroforese , Nanoporos , Eletricidade , Eletro-Osmose , Eletricidade Estática
8.
Electrophoresis ; 42(7-8): 834-868, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33382088

RESUMO

Electroosmotic flow (EOF), a consequence of an imposed electric field onto an electrolyte solution in the tangential direction of a charged surface, has emerged as an important phenomenon in electrokinetic transport at the micro/nanoscale. Because of their ability to efficiently pump liquids in miniaturized systems without incorporating any mechanical parts, electroosmotic methods for fluid pumping have been adopted in versatile applications-from biotechnology to environmental science. To understand the electrokinetic pumping mechanism, it is crucial to identify the role of an ionically polarized layer, the so-called electrical double layer (EDL), which forms in the vicinity of a charged solid-liquid interface, as well as the characteristic length scale of the conducting media. Therefore, in this tutorial review, we summarize the development of electrical double layer models from a historical point of view to elucidate the interplay and configuration of water molecules and ions in the vicinity of a solid-liquid interface. Moreover, we discuss the physicochemical phenomena owing to the interaction of electrical double layer when the characteristic length of the conducting media is decreased from the microscale to the nanoscale. Finally, we highlight the pioneering studies and the most recent works on electro osmotic flow devoted to both theoretical and experimental aspects.


Assuntos
Eletro-Osmose , Microfluídica , Íons
9.
J Chem Phys ; 154(14): 144503, 2021 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-33858173

RESUMO

Molecular dynamics simulations of water adsorbed in Material Institute Lavoisier MIL-101(Cr) metal-organic frameworks are performed to analyze the kinetic properties of water molecules confined in the framework at 298.15 K and under different vapor pressures and clarify the water adsorption mechanism in MIL-101(Cr). The terahertz frequency-domain spectra (THz-FDS) of water are calculated by applying fast Fourier transform to the configurational data of water molecules. According to the characteristic frequencies in the THz-FDS, the dominant motions of water molecules in MIL-101(Cr) can be categorized into three types: (1) low-frequency translational motion (0-0.5 THz), (2) medium-frequency vibrational motion (2-2.5 THz), and (3) high-frequency vibrational motion (>6 THz). Each type of water motion is confirmed by visualizing the water configuration in MIL-101(Cr). The ratio of the number of water molecules with low-frequency translational motion to the total number of water molecules increases with the increase in vapor pressure. In contrast, that with medium-frequency vibrational motion is found to decrease with vapor pressure, exhibiting a pronounced decrease after water condensation has started in the cavities. That with the high-frequency vibrational motion is almost independent of the vapor pressure. The interactions between different types of water molecules affect the THz-FDS. Furthermore, the self-diffusion coefficient and the velocity auto-correlation function are calculated to clarify the adsorption state of the water confined in MIL-101(Cr). To confirm that the general trend of the THz-FDS does not depend on the water model, the simulations are performed using three water models, namely, rigid SPC/E, flexible SPC/E, and rigid TIP5PEw.

10.
Langmuir ; 35(33): 10762-10771, 2019 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-31345034

RESUMO

The effect of pore length on the water filling and emptying rates was studied using mesoporous silica (MPS) with same pore diameter but different pore lengths. The pore diameter of the synthesized MPS was ∼8 nm, whereas the average pore lengths were 460, 1,770, and 4000 nm. The gravimetric method was employed to record the time course of the adsorbed mass of water in MPS at 298 K and 1 atm. In both the filling and emptying processes, the relaxation curves (time course of adsorbed mass of water per unit mass of sample) were not significantly related to the pore length. This independence of the initial adsorption and desorption rates on the pore length suggests that the surface of the MPS aggregates is the bottleneck in the overall adsorption and desorption processes and that the initial mass flux in each nanopore is inversely proportional to the pore length. Furthermore, because the relaxation times to reach the equilibrium state were independent of the pore length, the mass flux of water uptake, release, and transport probably increase with an increase in the pore length during the entire adsorption and desorption processes. A transport model to describe these phenomena was proposed.

11.
J Biol Chem ; 290(34): 20748-20760, 2015 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-26134564

RESUMO

Glutamate is the principal excitatory neurotransmitter in the mammalian CNS. By analyzing the metabolic incorporation of azidohomoalanine, a methionine analogue, in newly synthesized proteins, we find that glutamate treatments up-regulate protein translation not only in intact rat cortical neurons in culture but also in the axons emitting from cortical neurons before making synapses with target cells. The process by which glutamate stimulates local translation in axons begins with the binding of glutamate to the ionotropic AMPA receptors and metabotropic glutamate receptor 1 and members of group 2 metabotropic glutamate receptors on the plasma membrane. Subsequently, the activated mammalian target of rapamycin (mTOR) signaling pathway and the rise in Ca(2+), resulting from Ca(2+) influxes through calcium-permeable AMPA receptors, voltage-gated Ca(2+) channels, and transient receptor potential canonical channels, in axons stimulate the local translation machinery. For comparison, the enhancement effects of brain-derived neurotrophic factor (BDNF) on the local protein synthesis in cortical axons were also studied. The results indicate that Ca(2+) influxes via transient receptor potential canonical channels and activated the mTOR pathway in axons also mediate BDNF stimulation to local protein synthesis. However, glutamate- and BDNF-induced enhancements of translation in axons exhibit different kinetics. Moreover, Ca(2+) and mTOR signaling appear to play roles carrying different weights, respectively, in transducing glutamate- and BDNF-induced enhancements of axonal translation. Thus, our results indicate that exposure to transient increases of glutamate and more lasting increases of BDNF would stimulate local protein synthesis in migrating axons en route to their targets in the developing brain.


Assuntos
Axônios/efeitos dos fármacos , Ácido Glutâmico/farmacologia , Receptores de AMPA/agonistas , Receptores de Glutamato Metabotrópico/agonistas , Sinapses/efeitos dos fármacos , Alanina/análogos & derivados , Alanina/metabolismo , Animais , Axônios/metabolismo , Axônios/ultraestrutura , Fator Neurotrófico Derivado do Encéfalo/genética , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Canais de Cálcio/genética , Canais de Cálcio/metabolismo , Sinalização do Cálcio , Embrião de Mamíferos , Regulação da Expressão Gênica no Desenvolvimento , Ácido Glutâmico/metabolismo , Hipocampo/citologia , Hipocampo/efeitos dos fármacos , Hipocampo/crescimento & desenvolvimento , Hipocampo/metabolismo , Cinética , Cultura Primária de Células , Biossíntese de Proteínas , Ratos , Ratos Sprague-Dawley , Receptores de AMPA/genética , Receptores de AMPA/metabolismo , Receptores de Glutamato Metabotrópico/genética , Receptores de Glutamato Metabotrópico/metabolismo , Sinapses/metabolismo , Sinapses/ultraestrutura , Serina-Treonina Quinases TOR/genética , Serina-Treonina Quinases TOR/metabolismo , Canais de Cátion TRPV/genética , Canais de Cátion TRPV/metabolismo , Ácido alfa-Amino-3-hidroxi-5-metil-4-isoxazol Propiônico/metabolismo
12.
Anal Chem ; 88(18): 9251-8, 2016 09 20.
Artigo em Inglês | MEDLINE | ID: mdl-27571138

RESUMO

The control of biomolecule translocation through nanopores is important in nanopore protein detection. Improvement in current nanopore molecule control is desired to enhance capture rates, extend translocation times, and ensure the effective detection of various proteins in the same solutions. We present a method that simultaneously resolves these issues through the use of a gate-modulated conical nanopore coupled with solutions of varying salt concentration. Simulation results show that the presence of an induced reverse electroosmotic flow (IREOF) results in inlet flows from the two ends of the nanopore centerline entering into the nanopore in opposite directions, which simultaneously elevates the capture rate and immobilizes the protein in the nanopore, thus enabling steady current blockage measurements for a range of proteins. In addition, it is shown that proteins with different size/charge ratios can be trapped by a gate modulation intensified flow field at a similar location in the nanopore in the same solution conditions.


Assuntos
Eletro-Osmose/instrumentação , Nanoporos , Proteínas/análise , Algoritmos , Técnicas Biossensoriais , Eletricidade , Desenho de Equipamento , Nanoporos/ultraestrutura , Pressão Osmótica , Transporte Proteico , Sais/química
13.
J Neurosci ; 34(29): 9574-89, 2014 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-25031400

RESUMO

cAMP-responsive element binding protein (CREB) phosphorylation and signaling plays an important role in long-term memory formation, but other posttranslational modifications of CREB are less known. Here, we found that CREB1Δ, the short isoform of CREB, could be sumoylated by the small ubiquitin-like modifier (SUMO) E3 ligase protein inhibitor of activated STAT1 (PIAS1) at Lys271 and Lys290 and PIAS1 SUMOylation of CREB1Δ increased the expression level of CREB1Δ. CREB1Δ could also be sumoylated by other PIAS family proteins, but not by the E3 ligases RanBP2 and Pc2 or by the E2 ligase Ubc9. Furthermore, water maze training increased the level of endogenous CREB SUMOylation in rat CA1 neurons determined by in vitro SUMOylation assay, but this effect was not observed in other brain areas. Moreover, transduction of Lenti-CREBWT to rat CA1 area facilitated, whereas transduction of Lenti-CREB double sumo-mutant (CREBK271RK290R) impaired, spatial learning and memory performance. Transduction of Lenti-CREBWT-SUMO1 fusion vector to rat CA1 area showed a more significant effect in enhancing spatial learning and memory and CREB SUMOylation. Lenti-CREBWT transduction increased, whereas Lenti-CREBK271RK290R transduction decreased, CREB DNA binding to the brain-derived neurotrophic factor (bdnf) promoter and decreased bdnf mRNA expression. Knock-down of PIAS1 expression in CA1 area by PIAS1 siRNA transfection impaired spatial learning and memory and decreased endogenous CREB SUMOylation. In addition, CREB SUMOylation was CREB phosphorylation dependent and lasted longer. Therefore, CREB phosphorylation may be responsible for signal transduction during the early phase of long-term memory formation, whereas CREB SUMOylation sustains long-term memory.


Assuntos
Proteína de Ligação ao Elemento de Resposta ao AMP Cíclico/metabolismo , Memória/fisiologia , Proteínas Inibidoras de STAT Ativados/metabolismo , Percepção Espacial/fisiologia , Sumoilação/fisiologia , Sequência de Aminoácidos , Animais , Proteína de Ligação ao Elemento de Resposta ao AMP Cíclico/genética , Regulação da Expressão Gênica/efeitos dos fármacos , Regulação da Expressão Gênica/genética , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Células HEK293 , Hipocampo/metabolismo , Humanos , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Aprendizagem em Labirinto/fisiologia , Memória/efeitos dos fármacos , Ligação Proteica/genética , Proteínas Inibidoras de STAT Ativados/genética , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Ratos , Ratos Sprague-Dawley , Transdução de Sinais/genética , Sumoilação/efeitos dos fármacos , Sumoilação/genética , Fatores de Tempo
14.
Mol Cell Neurosci ; 61: 141-51, 2014 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-24983517

RESUMO

Local synthesis of proteins in the axons participates in axonogenesis and axon guidance to establish appropriate synaptic connections and confer plasticity. To study the transcripts present in the growth cones and axonal shafts of cultured rat hippocampal neurons, two chip devices, differing in their abilities to support axonal growth and branching, are designed and employed here to isolate large quantities of axonal materials. Cone-, shaft- and axon-residing transcripts with amounts higher than that of a somatodendritic transcript, Actg1 (γ-actin), are selected and classified. Since the chips are optically transparent, distribution of transcripts over axons can be studied by fluorescence in situ hybridization. Three transcripts, Cadm1 (cell adhesion molecule 1), Nefl (neurofilament light polypeptide), and Cfl1 (non-muscle cofilin) are confirmed to be preferentially localized to the growth cones, while Pfn2 (profilin2) is preferentially localized to the shafts of those axons growing on the chip that restricts axonal growth. The different growing conditions of axons on chips and on conventional coverslips do not affect the cone-preferred localization of Cadm1 and shaft-preferred localization of Pfn2, but affect the distributions of Nefl and Cfl1 over the axons at 14th day in vitro. Furthermore, the distributions of Cadm1 and Nefl over the axons growing on conventional coverslips undergo changes during in vitro development. Our results suggest a dynamic nature of the mechanisms regulating the distributions of transcripts in axonal substructures in a manner dependent upon both growth conditions and neuronal maturation.


Assuntos
Cones de Crescimento/metabolismo , Hipocampo/citologia , Microdomínios da Membrana/metabolismo , Neurônios/citologia , Actinas/genética , Actinas/metabolismo , Fatores Etários , Animais , Moléculas de Adesão Celular/genética , Moléculas de Adesão Celular/metabolismo , Células Cultivadas , Cofilina 1/genética , Cofilina 1/metabolismo , Embrião de Mamíferos , Feminino , Produtos do Gene nef/genética , Produtos do Gene nef/metabolismo , Hibridização in Situ Fluorescente , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Gravidez , Profilinas/genética , Profilinas/metabolismo , RNA Ribossômico 18S/metabolismo , Ratos , Ratos Sprague-Dawley
15.
Nano Lett ; 14(1): 225-30, 2014 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-24329425

RESUMO

Holograms, the optical devices to reconstruct predesigned images, show many applications in our daily life. However, applications of hologram are still limited by the constituent materials and therefore their working range is trapped at a particular electromagnetic region. In recent years, the metasurfaces, an array of subwavelength antenna with varying sizes, show the abilities to manipulate the phase of incident electromagnetic wave from visible to microwave frequencies. Here, we present a reflective-type and high-efficiency meta-hologram fabricated by metasurface for visible wavelength. Using gold cross nanoantennas as building blocks to construct our meta-hologram devices with thickness ∼ λ/4, the reconstructed images of meta-hologram show polarization-controlled dual images with high contrast, functioning for both coherent and incoherent light sources within a broad spectral range and under a wide range of incidence angles. The flexibility demonstrated here for our meta-hologram paves the road to a wide range of applications related to holographic images at arbitrary electromagnetic wave region.


Assuntos
Ouro/química , Holografia/instrumentação , Lentes , Nanopartículas Metálicas/química , Nanopartículas Metálicas/ultraestrutura , Nanotecnologia/instrumentação , Refratometria/instrumentação , Desenho de Equipamento , Análise de Falha de Equipamento
16.
BMC Bioinformatics ; 15 Suppl 17: S4, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25559583

RESUMO

BACKGROUND: The earliest whole protein order/disorder predictor (Uversky et al., Proteins, 41: 415-427 (2000)), herein called the charge-hydropathy (C-H) plot, was originally developed using the Kyte-Doolittle (1982) hydropathy scale (Kyte & Doolittle., J. Mol. Biol, 157: 105-132(1982)). Here the goal is to determine whether the performance of the C-H plot in separating structured and disordered proteins can be improved by using an alternative hydropathy scale. RESULTS: Using the performance of the CH-plot as the metric, we compared 19 alternative hydropathy scales, with the finding that the Guy (1985) hydropathy scale (Guy, Biophys. J, 47:61-70(1985)) was the best of the tested hydropathy scales for separating large collections structured proteins and intrinsically disordered proteins (IDPs) on the C-H plot. Next, we developed a new scale, named IDP-Hydropathy, which further improves the discrimination between structured proteins and IDPs. Applying the C-H plot to a dataset containing 109 IDPs and 563 non-homologous fully structured proteins, the Kyte-Doolittle (1982) hydropathy scale, the Guy (1985) hydropathy scale, and the IDP-Hydropathy scale gave balanced two-state classification accuracies of 79%, 84%, and 90%, respectively, indicating a very substantial overall improvement is obtained by using different hydropathy scales. A correlation study shows that IDP-Hydropathy is strongly correlated with other hydropathy scales, thus suggesting that IDP-Hydropathy probably has only minor contributions from amino acid properties other than hydropathy. CONCLUSION: We suggest that IDP-Hydropathy would likely be the best scale to use for any type of algorithm developed to predict protein disorder.


Assuntos
Aminoácidos/química , Bases de Dados de Proteínas , Proteínas Intrinsicamente Desordenadas/química , Proteínas/química , Proteínas/classificação , Algoritmos , Animais , Humanos , Interações Hidrofóbicas e Hidrofílicas
17.
Anal Chem ; 86(17): 8711-8, 2014 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-25098739

RESUMO

Isoelectric focusing of proteins in a silica nanofluidic channel filled with citric acid and disodium phosphate buffers is investigated via numerical simulation. Ions in the channel migrate in response to (i) the electric field acting on their charge and (ii) the bulk electroosmotic flow (which is directed toward the cathode). Proteins are focused near the low pH (anode) end when the electromigration effect is more significant and closer to the high pH (cathode) end when the electroosmotic effect dominates. We simulate the focusing behavior of Dylight labeled streptavidin (Dyl-Strep) proteins in the channel, using a relationship between the protein's charge and pH measured in a previous experiment. Protein focusing results compare well to previous experimental measurements. The effect of some key parameters, such as applied voltage, isoelectric point (pI), bulk pH, and bulk conductivity, on the protein trapping behavior in a nanofluidic channel is examined.


Assuntos
Nanotecnologia/métodos , Proteínas/química , Dióxido de Silício/química , Eletrodos , Eletro-Osmose , Concentração de Íons de Hidrogênio , Focalização Isoelétrica , Ponto Isoelétrico , Nanotecnologia/instrumentação
18.
Langmuir ; 30(18): 5337-48, 2014 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-24725102

RESUMO

Previous work has demonstrated the simultaneous concentration and separation of proteins via a stable ion concentration gradient established within a nanochannel (Inglis Angew. Chem., Int. Ed. 2001, 50, 7546-7550). To gain a better understanding of how this novel technique works, we here examine experimentally and numerically how the underlying electric potential controlled ion concentration gradients can be formed and controlled. Four nanochannel geometries are considered. Measured fluorescence profiles, a direct indicator of ion concentrations within the Tris-fluorescein buffer solution, closely match depth-averaged fluorescence profiles calculated from the simulations. The simulations include multiple reacting species within the fluid bulk and surface wall charge regulation whereby the deprotonation of silica-bound silanol groups is governed by the local pH. The three-dimensional system is simulated in two dimensions by averaging the governing equations across the (varying) nanochannel width, allowing accurate numerical results to be generated for the computationally challenging high aspect ratio nanochannel geometries. An electrokinetic circuit analysis is incorporated to directly relate the potential drop across the (simulated) nanochannel to that applied across the experimental chip device (which includes serially connected microchannels). The merit of the thick double layer, potential-controlled concentration gradient as a particle focusing and separation tool is discussed, linking this work to the previously presented protein trapping experiments. We explain why stable traps are formed when the flow is in the opposite direction to the concentration gradient, allowing particle separation near the low concentration end of the nanochannel. We predict that tapered, rather than straight nanochannels are better at separating particles of different electrophoretic mobilities.


Assuntos
Nanotecnologia/métodos , Concentração de Íons de Hidrogênio
19.
Sci Adv ; 10(16): eadn2752, 2024 Apr 19.
Artigo em Inglês | MEDLINE | ID: mdl-38630828

RESUMO

Nonlocal effects originating from interactions between neighboring meta-atoms introduce additional degrees of freedom for peculiar characteristics of metadevices, such as enhancement, selectivity, and spatial modulation. However, they are generally difficult to manipulate because of the collective responses of multiple meta-atoms. Here, we experimentally demonstrate the nonlocal metasurface to realize the spatial modulation of dark-field emission. Plasmonic asymmetric split rings (ASRs) are designed to simultaneously excite local dipole resonance and nonlocal quasi-bound states in the continuum and spatially extended modes. With one type of unit, nonlocal effects are tailored by varying array periods. ASRs at the metasurface's edge lack sufficient interactions, resulting in stronger dark-field scattering and thus edge emission properties of the metasurface. Pixel-level spatial control is demonstrated by simply erasing some units, providing more flexibility than conventional local metasurfaces. This work paves the way for manipulating nonlocal effects and facilitates applications in optical trapping and sorting at the nanoscale.

20.
Exploration (Beijing) ; 4(2): 20220110, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38855615

RESUMO

Artificial nanofluidic networks are emerging systems for blue energy conversion that leverages surface charge-derived permselectivity to induce voltage from diffusive ion transport under salinity difference. Here the pivotal significance of electrostatic inter-channel couplings in multi-nanopore membranes, which impose constraints on porosity and subsequently influence the generation of large osmotic power outputs, is illustrated. Constructive interference is observed between two 20 nm nanopores of 30 nm spacing that renders enhanced permselectivity to osmotic power output via the recovered electroneutrality. On contrary, the interference is revealed as destructive in two-dimensional arrays causing significant deteriorations of the ion selectivity even for the nanopores sparsely distributed at an order of magnitude larger spacing than the Dukhin length. Most importantly, a scaling law is provided for deducing the maximal membrane area and porosity to avoid the selectivity loss via the inter-pore electrostatic coupling. As the electric crosstalk is inevitable in any fluidic network, the present findings can be a useful guide to design nanoporous membranes for scalable osmotic power generations.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA