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1.
Biomed Pharmacother ; 175: 116724, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38761424

RESUMO

Metabolic dysfunction-associated steatotic liver disease (MASLD) has become one of the most prevalent liver diseases worldwide, and its occurrence is strongly associated with obesity, insulin resistance (IR), genetics, and metabolic stress. Ranging from simple fatty liver to metabolic dysfunction-associated steatohepatitis (MASH), even to severe complications such as liver fibrosis and advanced cirrhosis or hepatocellular carcinoma, the underlying mechanisms of MASLD progression are complex and involve multiple cellular mediators and related signaling pathways. Pattern recognition receptors (PRRs) from the innate immune system, including Toll-like receptors (TLRs), C-type lectin receptors (CLRs), NOD-like receptors (NLRs), RIG-like receptors (RLRs), and DNA receptors, have been demonstrated to potentially contribute to the pathogenesis for MASLD. Their signaling pathways can induce inflammation, mediate oxidative stress, and affect the gut microbiota balance, ultimately resulting in hepatic steatosis, inflammatory injury and fibrosis. Here we review the available literature regarding the involvement of PRR-associated signals in the pathogenic and clinical features of MASLD, in vitro and in animal models of MASLD. We also discuss the emerging targets from PRRs for drug developments that involved agent therapies intended to arrest or reverse disease progression, thus enabling the refinement of therapeutic targets that can accelerate drug development.


Assuntos
Receptores de Reconhecimento de Padrão , Humanos , Animais , Receptores de Reconhecimento de Padrão/metabolismo , Fígado Gorduroso/metabolismo , Transdução de Sinais , Imunidade Inata
2.
Nat Commun ; 15(1): 3399, 2024 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-38649376

RESUMO

The van der Waals antiferromagnetic topological insulator MnBi2Te4 represents a promising platform for exploring the layer-dependent magnetism and topological states of matter. Recently observed discrepancies between magnetic and transport properties have aroused controversies concerning the topological nature of MnBi2Te4 in the ground state. In this article, we demonstrate that fabrication can induce mismatched even-odd layer dependent magnetotransport in few-layer MnBi2Te4. We perform a comprehensive study of the magnetotransport properties in 6- and 7-septuple-layer MnBi2Te4, and reveal that both even- and odd-number-layer device can show zero Hall plateau phenomena in zero magnetic field. Importantly, a statistical survey of the optical contrast in more than 200 MnBi2Te4 flakes reveals that the zero Hall plateau in odd-number-layer devices arises from the reduction of the effective thickness during the fabrication, a factor that was rarely noticed in previous studies of 2D materials. Our finding not only provides an explanation to the controversies regarding the discrepancy of the even-odd layer dependent magnetotransport in MnBi2Te4, but also highlights the critical issues concerning the fabrication and characterization of 2D material devices.

3.
Mater Horiz ; 11(10): 2517-2527, 2024 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-38497122

RESUMO

H2O2 production via the two-electron oxygen reduction reaction (2e- ORR) offers a potential alternative to the current anthraquinone method owing to its efficiency and environmental friendliness. However, it is necessary to determine the structures of electrocatalysts with cost-effectiveness and high efficiency for future industrialization demand. Herein, a supramolecular catalyst composed of cobalt-phthalocyanine on a near-monodispersed and oxidized single-walled carbon nanotube (CoPc/o-SWCNT) was synthesized via a solution self-assembly method for catalyzing the 2e- ORR for H2O2 electrosynthesis. Benefiting from the enhanced intermolecular interaction by introducing oxygen functional groups on o-SWCNTs, the oxidation states of single-atom Co sites were tuned via the formation of two extra Co-O bonds. Coupled with structural characterizations, density-functional theory (DFT) calculations reveal that the depressed d-band center of the Co site regulated by two axially-bridged O atoms gives rise to a suitable binding strength of oxygen intermediates (*OOH) to favor the 2e- ORR. Thus, the CoPc-6wt%/o-SWCNT-2 catalyst with optimized synthetic parameters delivers competitive 2e- ORR performance for H2O2 electrosynthesis in a neutral electrolyte (pH = 7), including enhanced H2O2 generation, satisfactory molar selectivity of ∼83-95% and long-period stability (75 h) in H-cell measurement. Moreover, it could also be boosted to show a high current of 45 mA cm-2, recorded turnover frequency of 25.3 ± 0.5 s-1 and maximum H2O2 production rate of 5.85 mol g-1 h-1 with a continuous H2O2 accumulation of 1.2 wt% in a flow-cell device, which outperformed most of the reported neutral-selective nonprecious metal single-atom catalysts.

4.
Adv Mater ; 36(16): e2308597, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38288654

RESUMO

Polymer dielectric capacitors are fundamental in advanced electronics and power grids but suffer from low energy density, hindering miniaturization of compact electrical systems. It is shown that high-energy and strong penetrating γ-irradiation significantly enhances capacitive energy storage performance of polymer dielectrics. γ-irradiated biaxially oriented polypropylene (BOPP) films exhibit an extraordinarily high energy density of 10.4 J cm-3 at 968 MV m-1 with an efficiency of 97.3%. In particular, an energy density of 4.06 J cm-3 with an ultrahigh efficiency of 98% is reliably maintained through 20 000 charge-discharge cycles under 600 MV m-1. At 125 °C, the γ-irradiated BOPP film still delivers a high discharged energy density of 5.88 J cm-3 with an efficiency of 90% at 770 MV m-1. Substantial improvements are also achieved for γ-irradiated cycloolefin copolymers at a high temperature of 150 °C, verifying the strategy generalizability. Experimental and theoretical analyses reveal that the excellent performance should be related to the γ-irradiation induced polar functional groups with high electron affinity in the molecular chain, which offer deep energy traps to impede charge transport. This work provides a simple and generally applicable strategy for developing high-performance polymer dielectrics.

5.
Nanotechnology ; 35(2)2023 Oct 27.
Artigo em Inglês | MEDLINE | ID: mdl-37797607

RESUMO

Two-electron oxygen reduction reaction (2e-ORR) for H2O2production is regarded as a more ecologically friendly substitute to the anthraquinone method. However, the search of selective and cheap catalysts is still challenging. Herein, we developed a neutral-selective and efficient nonprecious electrocatalyst that was prepared from a commercial activated carbon (AC) by simply microwave-assisted ash impurity elimination and hydrogen peroxide oxidation for surface functional sites optimization. The oxygen configuration can be tuned with enriching carboxyl group up to 6.65 at.% by the dosage of hydrogen peroxide (mass ratio of H2O2/C = ∼0-8.3). Chemical titration experiments identified the carbonyl groups as the most potential active sites, with selectivity boosted by the additional carboxyl groups. The microwave-assisted moderate-oxidized activated carbon (MW-AC5.0) demonstrated optimal 2e-ORR activity and selectivity in neutral electrolyte (0.1 M K2SO4), with H2O2selectivity reaching ∼75%-97%, a maximum H2O2production rate (1.90 mol·gcatal-1·h-1@0.1 V) and satisfying faradaic efficiency (∼85%) in gas-diffusion-electrode. When coupled with Fenton reaction, it can degrade a model organic pollutant (methylene blue [MB], 50 ppm) to colorless in a short time of 20 min, indicating the potential applications in the environmental remediation.

6.
Nanotechnology ; 34(48)2023 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-37625396

RESUMO

Extensive investigations have been devoted to nitrogen-doped carbon materials as catalysts for the oxygen reduction reaction (ORR) in various conversion technologies. In this study, we introduce nitrogen-doped carbon materials with hollow spherical structures. These materials demonstrate significant potential in ORR activity within alkaline media, showing a half-wave potential of 0.87 V versus the reversible hydrogen electrode (RHE). Nitrogen-doped hollow carbon spheres (N-CHS) exhibit unique characteristics such as a thin carbon shell layer, hollow structure, large surface area, and distinct pore features. These features collectively create an optimal environment for facilitating the diffusion of reactants, thereby enhancing the exposure of active sites and improving catalytic performance. Building upon the promising qualities of N-CHS as a catalyst support, we employ heme chloride (1 wt%) as the source of iron for Fe doping. Through the carbonization process, Fe-N active sites are effectively formed, displaying a half-wave potential of 0.9 V versus RHE. Notably, when implemented as a cathode catalyst in zinc-air batteries, this catalyst exhibits an impressive power density of 162.6 mW cm-2.

7.
Sci Bull (Beijing) ; 68(12): 1252-1258, 2023 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-37268443

RESUMO

The recently discovered antiferromagnetic (AFM) topological insulator (TI) MnBi2Te4 represents a versatile material platform for exploring exotic topological quantum phenomena in nanoscale devices. It has been proposed that even-septuple-layer (even-SL) MnBi2Te4 can host helical hinge currents with unique nonlocal behavior, but experimental confirmation is still lacking. In this work, we report transport studies of exfoliated MnBi2Te4 flakes with varied thicknesses down to the few-nanometer regime. We observe giant nonlocal transport signals in even-SL devices when the system is in the axion insulator state but vanishingly small nonlocal signal in the odd-SL devices at the same magnetic field range. In conjunction with theoretical calculations, we demonstrate that the nonlocal transport is via the helical edge currents mainly distributed at the hinges between the side and top/bottom surfaces. The helical edge currents in the axion insulator state may find unique applications in topological quantum devices.

8.
Anal Bioanal Chem ; 415(17): 3363-3374, 2023 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-37154935

RESUMO

As the most abundant protein in plasma, human serum albumin plays a vital role in physiological processes, such as maintaining blood osmotic pressure and carrying small-molecule ligands. Since the content of albumin in the human serum can reflect the status of liver and renal function, albumin quantitation is significant in clinical diagnosis. In this work, fluorescence turn-on detection of human serum albumin (HSA) had been performed based on the assembly of gold nanoclusters and bromocresol green. Gold nanoclusters (AuNCs) capped by reduced glutathione (GSH) were assembled with bromocresol green (BCG), and the assembly was used as a fluorescent probe for HSA. After BCG assembling, the fluorescence of gold nanoclusters was nearly quenched. In acidic solution, HSA can selectively bind to BCG on the assembly and recover the fluorescence of the solution. Based on this turn-on fluorescence, ratiometric HSA quantification was realized. Under optimal conditions, HSA detection by the probe possessed a good linear relationship in the range of 0.40-22.50 mg·mL-1, and the detection limit was 0.27 ± 0.04 mg·mL-1 (3σ, n = 3). Common coexisting components in serum and blood proteins did not interfere with the detection of HSA. This method has the advantages of easy manipulation and high sensitivity, and the fluorescent response is insensitive to reaction time.


Assuntos
Nanopartículas Metálicas , Albumina Sérica Humana , Humanos , Verde de Bromocresol , Espectrometria de Fluorescência/métodos , Ouro , Corantes Fluorescentes
9.
bioRxiv ; 2023 Mar 10.
Artigo em Inglês | MEDLINE | ID: mdl-36945479

RESUMO

The human cerebral cortex is connected by intricate inter-areal wiring at the macroscale. The cortical hierarchy from primary sensorimotor to higher-order association areas is a unifying organizational principle across various neurobiological properties; however, previous studies have not clarified whether the connections between cortical regions exhibit a similar hierarchical pattern. Here, we identify a connectional hierarchy indexed by inter-individual variability of functional connectivity edges, which continuously progresses along a hierarchical gradient from within-network connections to between-network edges connecting sensorimotor and association networks. We found that this connectional hierarchy of variability aligns with both hemodynamic and electromagnetic connectivity strength and is constrained by structural connectivity strength. Moreover, the patterning of connectional hierarchy is related to inter-regional similarity in transcriptional and neurotransmitter receptor profiles. Using the Neurosynth cognitive atlas and cortical vulnerability maps in 13 brain disorders, we found that the connectional hierarchy of variability is associated with similarity networks of cognitive relevance and that of disorder vulnerability. Finally, we found that the prominence of this hierarchical gradient of connectivity variability declines during youth. Together, our results reveal a novel hierarchal organizational principle at the connectional level that links multimodal and multiscale human connectomes to individual variability in functional connectivity.

10.
Sensors (Basel) ; 23(6)2023 Mar 09.
Artigo em Inglês | MEDLINE | ID: mdl-36991679

RESUMO

As an essential indicator of liver function, bilirubin is of great significance for clinical diagnosis. A non-enzymatic sensor has been established for sensitive bilirubin detection based on the bilirubin oxidation catalyzed by unlabeled gold nanocages (GNCs). GNCs with dual-localized surface plasmon resonance (LSPR) peaks were prepared by a one-pot method. One peak around 500 nm was ascribed to gold nanoparticles (AuNPs), and the other located in the near-infrared region was the typical peak of GNCs. The catalytic oxidation of bilirubin by GNCs was accompanied by the disruption of cage structure, releasing free AuNPs from the nanocage. This transformation changed the dual peak intensities in opposite trend, and made it possible to realize the colorimetric sensing of bilirubin in a ratiometric mode. The absorbance ratios showed good linearity to bilirubin concentrations in the range of 0.20~3.60 µmol/L with a detection limit of 39.35 nM (3σ, n = 3). The sensor exhibited excellent selectivity for bilirubin over other coexisting substances. Bilirubin in real human serum samples was detected with recoveries ranging from 94.5 to 102.6%. The method for bilirubin assay is simple, sensitive and without complex biolabeling.


Assuntos
Ouro , Nanopartículas Metálicas , Humanos , Ouro/química , Colorimetria/métodos , Bilirrubina , Nanopartículas Metálicas/química , Catálise
11.
Nanomaterials (Basel) ; 12(8)2022 Apr 12.
Artigo em Inglês | MEDLINE | ID: mdl-35458035

RESUMO

Low-frequency electronic noise is an important parameter used for the electronic and sensing applications of transistors. Here, we performed a systematic study on the low-frequency noise mechanism for both p-channel and n-channel MoTe2 field-effect transistors (FET) at different temperatures, finding that low-frequency noise for both p-type and n-type conduction in MoTe2 devices come from the variable range hopping (VRH) transport process where carrier number fluctuations (CNF) occur. This process results in the broad distribution of the waiting time of the carriers between successive hops, causing the noise to increase as the temperature decreases. Moreover, we found the noise magnitude for p-type MoTe2 FET hardly changed after exposure to the ambient conditions, whereas for n-FET, the magnitude increased by nearly one order. These noise characteristics may provide useful guidelines for developing high-performance electronics based on the emerging transition metal dichalcogenides.

12.
Anal Bioanal Chem ; 413(28): 7009-7019, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34535815

RESUMO

Serum bilirubin is an important indicator to assess liver function and diagnose various types of liver diseases. The level of serum bilirubin is also negatively correlated with the risk of cardiovascular disease and cancer. We had fabricated a fluorescent film sensor aiming at free bilirubin detection at the nanomolar level. Gold nanoclusters capped by human serum albumin (HSA-AuNCs) were utilized as a fluorescent platform for bilirubin biorecognition. HSA-AuNCs were functionalized with glucuronic acid to increase the binding sites for bilirubin. An ultrathin film of glucuronic acid-functionalized gold nanoclusters was obtained by the Langmuir-Blodgett (LB) technique. When exposed to bilirubin, the interaction between free bilirubin and the functionalized AuNCs resulted in fluorescent quenching of the film. Good linearity could be achieved for the quenching efficiency versus the logarithm of free bilirubin concentration over a concentration range of 1.00 nM~5.00 µM. The limit of detection (LOD) was calculated to be (2.70 ± 0.14) × 10-1 nM (S/N = 3). The film sensor presents a good anti-interference capability towards common substances coexisting with bilirubin in serum. Satisfactory results achieved in the tests of real serum samples indicate that the LB film sensor can be used for bilirubin determination in nanomolar concentration.


Assuntos
Bilirrubina/análise , Ácido Glucurônico/química , Ouro/química , Nanopartículas Metálicas/química , Nanoestruturas/química , Espectrometria de Fluorescência/métodos , Humanos , Limite de Detecção , Albumina Sérica Humana/química
13.
Nat Commun ; 12(1): 4647, 2021 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-34330926

RESUMO

The intrinsic antiferromagnetic topological insulator MnBi2Te4 provides an ideal platform for exploring exotic topological quantum phenomena. Recently, the Chern insulator and axion insulator phases have been realized in few-layer MnBi2Te4 devices at low magnetic field regime. However, the fate of MnBi2Te4 in high magnetic field has never been explored in experiment. In this work, we report transport studies of exfoliated MnBi2Te4 flakes in pulsed magnetic fields up to 61.5 T. In the high-field limit, the Chern insulator phase with Chern number C = -1 evolves into a robust zero Hall resistance plateau state. Nonlocal transport measurements and theoretical calculations demonstrate that the charge transport in the zero Hall plateau state is conducted by two counter-propagating edge states that arise from the combined effects of Landau levels and large Zeeman effect in strong magnetic fields. Our result demonstrates the intricate interplay among intrinsic magnetic order, external magnetic field, and nontrivial band topology in MnBi2Te4.

14.
New Phytol ; 228(3): 932-945, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-32589757

RESUMO

Glandular secretory trichomes (GSTs) are regarded as biofactories for synthesizing, storing, and secreting artemisinin. It is necessary to figure out the initiation and development regulatory mechanism of GSTs to cultivate high-yielding Artemisia annua. Here, we identified an MYB transcription factor, AaTAR2, from bioinformatics analysis of the A. annua genome database and Arabidopsis trichome development-related genes. AaTAR2 is mainly expressed in young leaves and located in the nucleus. Repression and overexpression of AaTAR2 resulted in a decrease and increase, respectively, in the GSTs numbers, leaf biomass, and the artemisinin content in transgenic plants. Furthermore, the morphological characteristics changed obviously in trichomes, suggesting AaTAR2 plays a key role in trichome formation. In addition, the expression of flavonoid biosynthesis genes and total flavonoid content increased dramatically in AaTAR2-overexpressing transgenic plants. Owing to flavonoids possibly counteracting emerging resistance to artemisinin in Plasmodium species, AaTAR2 is a potential target to improve the effect of artemisinin in clinical therapy. Taken together, AaTAR2 positively regulates trichome development and artemisinin and flavonoid biosynthesis. A better understanding of this 'multiple functions' transcription factor may enable enhanced artemisinin and flavonoids yield. AaTAR2 is a potential breeding target for cultivating high-quality A. annua.


Assuntos
Artemisia annua , Artemisininas , Artemisia annua/genética , Melhoramento Vegetal , Proteínas de Plantas/genética , Plantas Geneticamente Modificadas , Tricomas
15.
Nat Mater ; 19(5): 522-527, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31907415

RESUMO

The intricate interplay between non-trivial topology and magnetism in two-dimensional materials can lead to the emergence of interesting phenomena such as the quantum anomalous Hall effect. Here we investigate the quantum transport of both bulk crystal and exfoliated MnBi2Te4 flakes in a field-effect transistor geometry. For the six septuple-layer device tuned into the insulating regime, we observe a large longitudinal resistance and zero Hall plateau, which are characteristics of an axion insulator state. The robust axion insulator state occurs in zero magnetic field, over a wide magnetic-field range and at relatively high temperatures. Moreover, a moderate magnetic field drives a quantum phase transition from the axion insulator phase to a Chern insulator phase with zero longitudinal resistance and quantized Hall resistance h/e2, where h is Planck's constant and e is electron charge. Our results pave the way for using even-number septuple-layer MnBi2Te4 to realize the quantized topological magnetoelectric effect and axion electrodynamics in condensed matter systems.

16.
Int J Nanomedicine ; 14: 3069-3086, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31118623

RESUMO

Background: Synthetic HDLs (sHDLs), small nanodiscs of apolipoprotein mimetic peptides surrounding lipid bilayers, were developed clinically for atheroma regression in cardiovascular patients. Formation of HDL involves interaction of apolipoprotein A-I (ApoA-I) with phospholipid bilayers and assembly into lipid-protein nanodiscs. Purpose: The objective of this study is to improve understanding of physico-chemical aspects of HDL biogenesis such as the thermodynamics of ApoA-I-peptide membrane insertion, lipid binding, and HDL self-assembly to improve our ability to form homogeneous sHDL nanodiscs that are suitable for clinical administration. Methods: The ApoA-I-mimetic peptide, 22A, was combined with either egg sphingomyelin (eSM) or 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) phospholipid vesicles to form sHDL. The sHDL assembly process was investigated through lipid vehicle solubilization assays and characterization of purity, size, and morphology of resulting nanoparticles via gel permeation chromatography (GPC), dynamic light scattering (DLS), and transmission electron microscopy (TEM). Peptide-lipid interactions involved were further probed by sum frequency generation (SFG) vibrational spectroscopy and attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR). The pharmacokinetics of eSM-sHDL and POPC-sHDL nanodiscs were investigated in Sprague Dawley rats. Results: sHDL formation was temperature-dependent, with spontaneous formation of sHDL nanoparticles occurring only at temperatures exceeding lipid transition temperatures as evidenced by DLS, GPC, and TEM characterization. SFG and ATR-FTIR spectroscopy findings support a change in peptide-lipid bilayer interactions at temperatures above the lipid transition temperature. Lipid-22A interactions were stronger with eSM than with POPC, which resulted in the formation of more homogeneous sHDL nanoparticles with longer in vivo circulation time as evidenced the PK study. Conclusion: Physico-chemical characteristics of sHDL are in part determined by phospholipid composition. Optimization of phospholipid composition may be utilized to improve the stability and homogeneity of sHDL.


Assuntos
Apolipoproteína A-I/metabolismo , Lipoproteínas HDL/metabolismo , Nanopartículas/química , Peptídeos/metabolismo , Fosfolipídeos/metabolismo , Sequência de Aminoácidos , Animais , Apolipoproteína A-I/química , Difusão Dinâmica da Luz , Cinética , Bicamadas Lipídicas/química , Lipoproteínas HDL/química , Masculino , Nanopartículas/ultraestrutura , Peptídeos/química , Peptídeos/farmacocinética , Fosfatidilcolinas/administração & dosagem , Ratos Sprague-Dawley , Solubilidade , Espectroscopia de Infravermelho com Transformada de Fourier , Esfingomielinas/administração & dosagem , Termodinâmica , Vibração
17.
Langmuir ; 34(22): 6538-6545, 2018 06 05.
Artigo em Inglês | MEDLINE | ID: mdl-29733605

RESUMO

Interfacial water structure on a polymer surface in water (or surface hydration) is related to the antifouling activity of the polymer. Zwitterionic polymer materials exhibit excellent antifouling activity due to their strong surface hydration. It was proposed to replace zwitterionic polymers using mixed charged polymers because it is much easier to prepare mixed charged polymer samples with much lower costs. In this study, using sum frequency generation (SFG) vibrational spectroscopy, we investigated interfacial water structures on mixed charged polymer surfaces in water and how such structures change while being exposed to salt solutions and protein solutions. The 1:1 mixed charged polymer exhibits excellent antifouling property whereas other mixed charged polymers with different ratios of the positive/negative charges do not. It was found that on the 1:1 mixed charged polymer surface, SFG water signal is dominated by the contribution of the strongly hydrogen bonded water molecules, indicating strong hydration of the polymer surface. The responses of the 1:1 mixed charged polymer surface to salt solutions are similar to those of zwitterionic polymers. Interestingly, exposure to high concentrations of salt solutions leads to stronger hydration of the 1:1 mixed charged polymer surface after replacing the salt solution with water. Protein molecules do not substantially perturb the interfacial water structure on the 1:1 mixed charged polymer surface and do not adsorb to the surface, showing that this mixed charged polymer is an excellent antifouling material.

18.
Chem Sci ; 9(7): 1769-1773, 2018 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-29675220

RESUMO

Two-dimensional (2D) materials such as graphene, molybdenum disulfide (MoS2), tungsten diselenide (WSe2), and black phosphorous are being developed for sensing applications with excellent selectivity and high sensitivity. In such applications, 2D materials extensively interact with various analytes including biological molecules. Understanding the interfacial molecular interactions of 2D materials with various targets becomes increasingly important for the progression of better-performing 2D-material based sensors. In this research, molecular interactions between several de novo designed alpha-helical peptides and monolayer MoS2 have been studied. Molecular dynamics simulations were used to validate experimental data. The results suggest that, in contrast to peptide-graphene interactions, peptide aromatic residues do not interact strongly with the MoS2 surface. It is also found that charged amino acids are important for ensuring a standing-up pose for peptides interacting with MoS2. By performing site-specific mutations on the peptide, we could mediate the peptide-MoS2 interactions to control the peptide orientation on MoS2.

19.
Phys Chem Chem Phys ; 20(2): 1021-1029, 2018 Jan 03.
Artigo em Inglês | MEDLINE | ID: mdl-29235592

RESUMO

Tethering peptides and proteins to abiotic surfaces has the potential to create biomolecule-functionalized surfaces with useful properties. Commonly used methods of immobilization lack control over the orientation in which biological molecules are covalently or physically bound to the surface, leading to sub-optimal materials. Here we use an engineered beta-galactosidase that can be chemically immobilized on a surface with a well-defined orientation through unique surface-accessible cysteine residues. A combined study using sum frequency generation (SFG) vibrational spectroscopy and coarse grained molecular dynamics (MD) simulations was performed to determine the effects of enzyme immobilization site and abiotic surface chemistry on enzyme surface orientation, surface coverage, and catalytic activity. Two beta-galactosidase variants that were immobilized through cysteine introduced at positions 227 and 308 were studied. In both cases, when the abiotic surface was made more hydrophilic, the enzyme surface coverage decreased, but the activity increased. MD simulations indicated that this is due to the weakened interactions between the immobilized enzyme and the more hydrophilic surface. These studies provide improved understanding of how enzyme-surface interactions can be optimized to maximize the catalytic activity of surface tethered enzymes.


Assuntos
Enzimas Imobilizadas/química , Simulação de Dinâmica Molecular , beta-Galactosidase/química , Cisteína , Peptídeos/química , Análise Espectral , Propriedades de Superfície , Vibração
20.
J Pharm Sci ; 107(2): 682-689, 2018 02.
Artigo em Inglês | MEDLINE | ID: mdl-29031976

RESUMO

Protein adsorbed at the silicone oil-water interface can undergo a conformational change that has the potential to induce protein aggregation on storage. Characterization of the protein structures at interface is therefore critical for understanding the protein-interface interactions. In this article, we have applied sum frequency generation (SFG) spectroscopy for studying the secondary structures of a fusion protein at interface and the surfactant effect on protein adsorption to silicone oil-water interface. SFG and chiral SFG spectra from adsorbed protein in the amide I region were analyzed. The presence of beta-sheet vibrational band at 1635 cm-1 implies the protein secondary structure was likely perturbed when protein adsorbed at silicone oil interface. The time-dependent SFG study showed a significant reduction in the SFG signal of preadsorbed protein when polysorbate 20 was introduced, suggesting surfactant has stronger interaction with the interface leading to desorption of protein from the interface. In the preadsorbed surfactant and a mixture of protein/polysorbate 20, SFG analysis confirmed that surfactant can dramatically prevent the protein adsorption to silicone oil surface. This study has demonstrated the potential of SFG for providing the detailed molecular level understanding of protein conformation at interface and assessing the influence of surfactant on protein adsorption behavior.


Assuntos
Proteínas/química , Óleos de Silicone/química , Água/química , Adsorção/efeitos dos fármacos , Polissorbatos/química , Estrutura Secundária de Proteína , Análise Espectral/métodos , Propriedades de Superfície , Tensoativos/química , Vibração
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