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1.
Proc Natl Acad Sci U S A ; 119(26): e2200158119, 2022 06 28.
Artículo en Inglés | MEDLINE | ID: mdl-35733257

RESUMEN

Mitochondrial preproteins synthesized in cytosol are imported into mitochondria by a multisubunit translocase of the outer membrane (TOM) complex. Functioned as the receptor, the TOM complex components, Tom 20, Tom22, and Tom70, recognize the presequence and further guide the protein translocation. Their deficiency has been linked with neurodegenerative diseases and cardiac pathology. Although several structures of the TOM complex have been reported by cryoelectron microscopy (cryo-EM), how Tom22 and Tom20 function as TOM receptors remains elusive. Here we determined the structure of TOM core complex at 2.53 Å and captured the structure of the TOM complex containing Tom22 and Tom20 cytosolic domains at 3.74 Å. Structural analysis indicates that Tom20 and Tom22 share a similar three-helix bundle structural feature in the cytosolic domain. Further structure-guided biochemical analysis reveals that the Tom22 cytosolic domain is responsible for binding to the presequence, and the helix H1 is critical for this binding. Altogether, our results provide insights into the functional mechanism of the TOM complex recognizing and transferring preproteins across the mitochondrial membrane.


Asunto(s)
Proteínas del Complejo de Importación de Proteínas Precursoras Mitocondriales , Receptores Citoplasmáticos y Nucleares , Microscopía por Crioelectrón , Humanos , Proteínas del Complejo de Importación de Proteínas Precursoras Mitocondriales/química , Dominios Proteicos , Receptores Citoplasmáticos y Nucleares/química
2.
Biochem Biophys Res Commun ; 715: 150004, 2024 Jun 30.
Artículo en Inglés | MEDLINE | ID: mdl-38678784

RESUMEN

Megakaryopoiesis and platelet production is a complex process that is underpotential regulation at multiple stages. Many long non-coding RNAs (lncRNAs) are distributed in hematopoietic stem cells and platelets. lncRNAs may play important roles as key epigenetic regulators in megakaryocyte differentiation and proplatelet formation. lncRNA NORAD can affect cell ploidy by sequestering PUMILIO proteins, although its direct effect on megakaryocyte differentiation and thrombopoiesis is still unknown. In this study, we demonstrate NORAD RNA is highly expressed in the cytoplasm during megakaryocyte differentiation. Interestingly, we identified for the first time that NORAD has a strong inhibitory effect on megakaryocyte differentiation and proplatelet formation from cultured megakaryocytes. DUSP6/ERK1/2 pathway is activated in response to NORAD knockdown during megakaryocytopoiesis, which is achieved by sequestering PUM2 proteins. Finally, compared with the wild-type control mice, NORAD knockout mice show a faster platelet recovery after severe thrombocytopenia induced by 6 Gy total body irradiation. These findings demonstrate lncRNA NORAD has a key role in regulating megakaryocyte differentiation and thrombopoiesis, which provides a promising molecular target for the treatment of platelet-related diseases such as severe thrombocytopenia.


Asunto(s)
Plaquetas , Diferenciación Celular , Fosfatasa 6 de Especificidad Dual , Megacariocitos , ARN Largo no Codificante , Trombopoyesis , Animales , Humanos , Ratones , Plaquetas/metabolismo , Diferenciación Celular/genética , Células Cultivadas , Fosfatasa 6 de Especificidad Dual/metabolismo , Fosfatasa 6 de Especificidad Dual/genética , Sistema de Señalización de MAP Quinasas , Megacariocitos/metabolismo , Megacariocitos/citología , Ratones Endogámicos C57BL , Ratones Noqueados , ARN Largo no Codificante/genética , ARN Largo no Codificante/metabolismo , Trombocitopenia/genética , Trombocitopenia/metabolismo , Trombocitopenia/patología , Trombopoyesis/genética
3.
Phys Chem Chem Phys ; 26(21): 15511-15518, 2024 May 29.
Artículo en Inglés | MEDLINE | ID: mdl-38752450

RESUMEN

Covalent organic frameworks (COFs) are an emerging class of crystalline organic materials that have shown potential to be a new physical platform. In this work, a designed COF named AB-COF, which has novel enantiomorphic Kagome bands, is proposed and a feasible route to synthesize it is given. Via a combination of first-principles calculations and tight-binding analysis, we investigate the electronic structures and the phase interference of the COF. It becomes topologically nontrivial when doping one iodine atom in a unit cell. The Berry curvatures of the valence band (VB) and conduction band (CB) of the iodine-doped AB-COF show opposite values and different distributions. This provides an opportunity to study the new mechanism of circular dichroism from the different Berry curvatures of the VB and CB. Surprisingly, the circular-dichroism dissymmetry factor of AB-COF reaches a theoretical maximum value, and the oscillator strength data are in agreement with this result. When two iodine atoms are doped in a unit cell, the Berry curvatures of the VB and CB also have different values, but with more symmetry and similar distributions. This behavior enhances the circular dichroism with a wider range of dissymmetric absorption, and the circular dichroism dissymmetry factor also reaches its theoretical maximum value.

4.
Phys Chem Chem Phys ; 26(3): 2066-2072, 2024 Jan 17.
Artículo en Inglés | MEDLINE | ID: mdl-38126725

RESUMEN

The kagome lattice is one of the most intriguing topics to study. It has a frustrated flat band touching a set of Dirac bands and can possess various promising properties, such as ferromagnetism, superconductivity, and a non-trivial topology. Covalent organic frameworks (COFs) are a rare type of inorganic material, however, they can provide a platform for generating certain required lattices. Based on first-principles density functional theory calculations, we show that a newly synthesized two-dimensional COF named COF-SH has novel enantiomorphic kagome bands, which include two sets of flat bands touching the Dirac bands around the Fermi level. The Bloch wave of the flat-valence band at the K-point shows the kagome nature of the phase interference. Under charge doping, the COF-SH exhibits a ferromagnetic ground state. Moreover, when COF-SH is doped with iodine atoms, a sizable gap in the system is opened between the flat bands and the Dirac bands due to the spin-orbit coupling (SOC) effect. Meanwhile, the spin degeneracy is lifted since the organic layer loses electrons due to the oxidizing property of iodine. In addition, our tight-binding analysis with the SOC effect shows that the flat valence band separates from the Dirac bands and holds a nonzero Chern number. Consequently, this I-doped COF can give rise to a quantum anomalous Hall effect.

5.
Environ Toxicol ; 39(4): 2429-2438, 2024 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-38197552

RESUMEN

OBJECTIVE: The development of drug resistance in hepatocellular carcinoma (HCC) cells limits the effectiveness of sorafenib (Sor). However, the regulatory mechanisms underlying the effects of the combination Sor and ropivacaine (Rop) on HCC cells remain unclear. METHODS: miR-224 and HOXD10 mRNA expression in HCC cells was analyzed using qRT-PCR. CCK-8, Transwell assays and tumor formation experiments in nude mice were used to assess HCC cell proliferation, migration, and invasion. Migration of HCC cells was also analyzed using a cell scratch assay. Hematoxylin and eosin staining was used to detect tumor area. RESULTS: miR-224 expression profoundly increased in HepG2 and Huh7 cells. Treatment with Rop and/or Sor blocked miR-244 expression, especially the combination treatment. Transfection of miR-224 mimic increased HCC cell proliferation and tumor size in nude mice, and migration and invasion in vitro in the presence of Rop and Sor compared to the negative control mimic. Dual-luciferase reporter assays showed that HOXD10 was targeted by miR-224. HOXD10 protein expression and was markedly reduced in HepG2 and Huh7 cells. Rop and/or Sor treatment increased HOXD10 protein expression, particularly the combination treatment. miR-224 negatively regulated HOXD10 expression in HCC cells treated with Rop and Sor. Transfection-mediated silencing of HOXD10 increased HCC cell proliferation, migration, and invasion in the presence of Rop and Sor compared with negative control transfection. CONCLUSION: The combination of Rop and Sor attenuates HCC cell proliferation and metastasis via the miR-224/HOXD10 axis.


Asunto(s)
Carcinoma Hepatocelular , Neoplasias Hepáticas , MicroARNs , Animales , Ratones , Carcinoma Hepatocelular/patología , Sorafenib/farmacología , Neoplasias Hepáticas/tratamiento farmacológico , Neoplasias Hepáticas/genética , Neoplasias Hepáticas/metabolismo , MicroARNs/genética , MicroARNs/metabolismo , Ratones Desnudos , Ropivacaína/farmacología , Línea Celular Tumoral , Proliferación Celular/genética , Movimiento Celular/genética , Regulación Neoplásica de la Expresión Génica
6.
Entropy (Basel) ; 26(1)2024 Jan 22.
Artículo en Inglés | MEDLINE | ID: mdl-38275502

RESUMEN

Evaluating the capabilities of a satellite communication system (SCS) is challenging due to its complexity and ambiguity. It is difficult to accurately analyze uncertain situations, making it difficult for experts to determine appropriate evaluation values. To address this problem, this paper proposes an innovative approach by extending the Dempster-Shafer evidence theory (DST) to the probabilistic hesitant fuzzy evidence theory (PHFET). The proposed approach introduces the concept of probabilistic hesitant fuzzy basic probability assignment (PHFBPA) to measure the degree of support for propositions, along with a combination rule and decision approach. Two methods are developed to generate PHFBPA based on multi-classifier and distance techniques, respectively. In order to improve the consistency of evidence, discounting factors are proposed using an entropy measure and the Jousselme distance of PHFBPA. In addition, a model for evaluating the degree of satisfaction of SCS capability requirements based on PHFET is presented. Experimental classification and evaluation of SCS capability requirements are performed to demonstrate the effectiveness and stability of the PHFET method. By employing the DST framework and probabilistic hesitant fuzzy sets, PHFET provides a compelling solution for handling ambiguous data in multi-source information fusion, thereby improving the evaluation of SCS capabilities.

7.
Small ; 19(14): e2206819, 2023 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-36592418

RESUMEN

Slippery and transparent polyvinyl alcohol (PVA) hydrogels with mechanical robustness exhibit broad applications in artificial biological soft tissues, flexible wearable electronics, and implantable biomedical devices. Most of the current PVA hydrogels, however, are unable to integrate these features, which compromises its performance in biological and engineering applications. To achieve such purpose, herein, a novel tactic is proposed, salting-out-after-syneresis of PVA, to realize a mechanically robust and highly transparent slippery PVA hydrogel. The syneresis of PVA sol is first conducted to form highly dense and transparent PVA polymer networks, then the salting-out effect tunes the aggregation of the polymer chains to rapidly induce the phase separation and crystallization. The resultant hydrogels show the transparency up to 98% in the visible region, the tribological coefficient down to 0.0081, and the excellent mechanical properties with strength, modulus, and toughness of 26.72 ± 1.05, 6.66 ± 0.29 MPa, and 55.21 ± 1.62 MJ m-3 , respectively. To reveal the potentials, PVA contact lens that combine remarkable lubrication, anti-protein adhesion, biocompatibility, and drug-loading functions are demonstrated. This strategy provides a simple and new avenue for developing the mechanically robust, transparent, and hydrated hydrogels, showing the potential in biomedicine and wearable devices.

8.
Chemistry ; 29(65): e202301294, 2023 Nov 21.
Artículo en Inglés | MEDLINE | ID: mdl-37589330

RESUMEN

Organic molecular field-effect transistors (FETs) are promising building components for future electronic circuits. Efficient control of charge transport properties is one key issue in the design of organic molecular FETs. In this study, we propose a redesign of a naphthalene-based FET by introducing two azulene components in opposite dipole moment directions. Using density functional theory combined with non-equilibrium Green's function, the simulated electronic transport characteristics reveal that the introduction of polar azulene components effectively narrows the frontier molecular orbitals gap, leading to an increase in the ON-state current. Meanwhile, the OFF-state current is significantly suppressed by highly localizing the dominant electronic transport channel. As a result, improved gate controllability is achieved with a higher ON-OFF current ratio, which is nearly seven times higher than that of the naphthalene-based FET device. These findings provide theoretical directions for future design of organic molecular FET devices with enhanced gating regulation efficiency.

9.
Langmuir ; 39(25): 8769-8778, 2023 Jun 27.
Artículo en Inglés | MEDLINE | ID: mdl-37307594

RESUMEN

Incorporating inorganic components into organic molecular devices offers one novel alternative to address challenges existing in the fabrication and integration of nanoscale devices. In this study, using a theoretical method of density functional theory combined with the nonequilibrium Green's function, a series of benzene-based molecules with group III and V substitutions, including borazine molecule and XnB3-nN3H6 (X = Al or Ga, n = 1-3) molecules/clusters, are constructed and investigated. An analysis of electronic structures reveals that the introduction of inorganic components effectively reduces the energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital, albeit at the cost of reduced aromaticity in these molecules/clusters. Simulated electronic transport characteristics demonstrate that XnB3-nN3H6 molecules/clusters coupled between metal electrodes exhibit lower conductance compared to prototypical benzene molecule. Additionally, the choice of metal electrode materials significantly impacts the electronic transport properties, with platinum electrode devices displaying distinct behavior compared to silver, copper, and gold electrode devices. This distinction arises from the amount of transferred charge, which modulates the alignment between molecular orbitals and the Fermi level of the metal electrodes by shifting the molecular orbitals in energy. These findings provide valuable theoretical insights for the future design of molecular devices incorporating inorganic substitutions.

10.
Nature ; 551(7678): 57-63, 2017 11 02.
Artículo en Inglés | MEDLINE | ID: mdl-29045394

RESUMEN

Life on Earth depends on photosynthesis for its conversion of solar energy to chemical energy. Photosynthetic organisms have developed a variety of light-harvesting systems to capture sunlight. The largest light-harvesting complex is the phycobilisome (PBS), the main light-harvesting antenna in cyanobacteria and red algae. It is composed of phycobiliproteins and linker proteins but the assembly mechanisms and energy transfer pathways of the PBS are not well understood. Here we report the structure of a 16.8-megadalton PBS from a red alga at 3.5 Å resolution obtained by single-particle cryo-electron microscopy. We modelled 862 protein subunits, including 4 linkers in the core, 16 rod-core linkers and 52 rod linkers, and located a total of 2,048 chromophores. This structure reveals the mechanisms underlying specific interactions between linkers and phycobiliproteins, and the formation of linker skeletons. These results provide a firm structural basis for our understanding of complex assembly and the mechanisms of energy transfer within the PBS.


Asunto(s)
Microscopía por Crioelectrón , Ficobilisomas/química , Ficobilisomas/ultraestructura , Rhodophyta/química , Rhodophyta/ultraestructura , Proteínas Algáceas/química , Proteínas Algáceas/metabolismo , Proteínas Algáceas/ultraestructura , Transferencia de Energía , Modelos Moleculares , Ficobilisomas/metabolismo , Subunidades de Proteína/química , Subunidades de Proteína/metabolismo
11.
Plant Dis ; 107(11): 3575-3584, 2023 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-37198724

RESUMEN

The recently emerged beech leaf disease (BLD) is causing the decline and death of American beech in North America. First observed in 2012 in northeast Ohio, U.S.A., BLD had been documented in 10 northeastern states and the Canadian province of Ontario as of July 2022. A foliar nematode has been implicated as the causal agent, along with some bacterial taxa. No effective treatments have been documented in the primary literature. Irrespective of potential treatments, prevention and prompt eradication (rapid responses) remain the most cost-effective approaches to the management of forest tree disease. For these approaches to be feasible, however, it is necessary to understand the factors that contribute to BLD spread and use them in estimation of risk. Here, we conducted an analysis of BLD risk across northern Ohio, western Pennsylvania, western New York, and northern West Virginia, U.S.A. In the absence of symptoms, an area cannot necessarily be deemed free of BLD (i.e., absence of BLD cannot be certain) due to its fast spread and the lag in symptom expression (latency) after infection. Therefore, we employed two widely used presence-only species distribution models (SDMs), one-class support vector machine (OCSVM), and maximum entropy (Maxent) to predict the spatial pattern of BLD risk based on BLD presence records and associated environmental variables. Our results show that both methods work well for BLD environmental risk modeling purposes, but Maxent outperforms OCSVM with respect to both the quantitative receiver operating characteristics (ROC) analysis and the qualitative evaluation of the spatial risk maps. Meanwhile, the Maxent model provides a quantification of variable contribution for different environmental factors, indicating that meteorological (isothermality and temperature seasonality) and land cover type (closed broadleaved deciduous forest) factors are likely key contributors to BLD distribution. Moreover, the future trajectories of BLD risk over our study area in the context of climate change were investigated by comparing the current and future risk maps obtained by Maxent. In addition to offering the ability to predict where the disease may spread next, our work contributes to the epidemiological characterization of BLD, providing new lines of investigation to improve ecological or silvicultural management. Furthermore, this study shows strong potential for extension of environmental risk mapping over the full American beech distribution range so that proactive management measures can be put in place. Similar approaches can be designed for other significant or emerging forest pest problems, contributing to overall management efficiency and efficacy.


Asunto(s)
Fagus , Estados Unidos , Bosques , New England , Hojas de la Planta , Ontario
12.
Glob Chang Biol ; 28(4): 1569-1582, 2022 02.
Artículo en Inglés | MEDLINE | ID: mdl-34854170

RESUMEN

Global climate change substantially influences vegetation spring phenology, that is, green-up date (GUD), in the northern permafrost region. Changes in GUD regulate ecosystem carbon uptake, further feeding back to local and regional climate systems. Extant studies mainly focused on the direct effects of climate factors, such as temperature, precipitation, and insolation; however, the responses of GUD to permafrost degradation caused by warming (i.e., indirect effects) remain elusive yet. In this study, we examined the impacts of permafrost degradation on GUD by analyzing the long-term trend of satellite-based GUD in relation to permafrost degradation measured by the start of thaw (SOT) and active layer thickness (ALT). We found significant trends of advancing GUD, SOT, and thickening ALT (p < 0.05), with a spatially averaged slope of -2.1 days decade-1 , -4.1 days decade-1 , and +1.1 cm decade-1 , respectively. Using partial correlation analyses, we found more than half of the regions with significantly negative correlations between spring temperature and GUD became nonsignificant after considering permafrost degradation. GUD exhibits dominant-positive (37.6% vs. 0.6%) and dominant-negative (1.8% vs. 35.1%) responses to SOT and ALT, respectively. Earlier SOT and thicker ALT would enhance soil water availability, thus alleviating water stress for vegetation green-up. Based on sensitivity analyses, permafrost degradation was the dominant factor controlling GUD variations in 41.7% of the regions, whereas only 19.6% of the regions were dominated by other climatic factors (i.e., temperature, precipitation, and insolation). Our results indicate that GUDs were more sensitive to permafrost degradation than direct climate change in spring among different vegetation types, especially in high latitudes. This study reveals the significant impacts of permafrost degradation on vegetation GUD and highlights the importance of permafrost status in better understanding spring phenological responses to future climate change.


Asunto(s)
Hielos Perennes , Cambio Climático , Ecosistema , Estaciones del Año , Temperatura
13.
Phys Chem Chem Phys ; 24(48): 29882-29890, 2022 Dec 14.
Artículo en Inglés | MEDLINE | ID: mdl-36468446

RESUMEN

Janus MoSSe with mirror asymmetry has recently emerged as a new two-dimensional (2D) material with a sizeable out-of-plane dipole moment. Here, based on first-principles calculations, we theoretically investigate the electronic properties of two patterns of 2D MoSSe/MoS2 van der Waals heterostructures (vdWHs). The electronic properties of MoSSe can be tuned by the intrinsic out-of-plane dipole field. When the Se side of the Janus layer faces the MoS2 layer, the dipole field points from the MoSSe layer towards the MoS2 layer, and the vdWH possesses a type-I band alignment which is desirable for light emission applications. With a reversal of the Janus layer, the intrinsic field inverts accordingly, and the band alignment becomes a typical type-II band alignment, which benefits carrier separation. Moreover, it possesses superior optical absorption (∼105 cm-1), and the calculated photocurrent density under visible-light radiation is up to 0.9 mA cm-2 in the MoSSe/MoS2 vdWH. Meanwhile, an external electric field and vertical strain can remarkably modulate the band alignment to switch it between type-I and type-II. Thus, MoSSe/MoS2 vdWHs have promising applications in next-generation photovoltaic devices.

14.
Phys Chem Chem Phys ; 23(38): 21641-21651, 2021 Oct 06.
Artículo en Inglés | MEDLINE | ID: mdl-34580681

RESUMEN

Semiconductor photocatalysts, using sunlight to stimulate various photocatalytic reactions, are promising materials for solving the energy crisis and environmental problems. However, the low photocatalytic efficiency and high cost pose major challenges for their widespread application. Mimicking the natural photosynthesis system, we propose a direct Z-scheme photocatalyst based on a Janus van der Waals heterostructure (vdWH) comprising SnC and Janus SeSnS monolayers. From first-principles calculations, the intrinsic built-in electric field of Janus SeSnS and the charge transfer from the SnC to the SeSnS layer give rise to a type-II band alignment. Such a band alignment benefits the formation of spatially separated reductive and oxidative active sites and the reduction of the global bandgap of the Janus vdWH. The proposed material increases the solar-to-hydrogen conversion efficiency to 60.8%. Besides, we also find that the light absorption coefficient is stacking configuration controllable and strain-tunable, e.g., the tensile strain promotes photocatalytic efficiency. Moreover, because Sn, S, and Se are environmentally benign and inexpensive elements, SnC/SeSnS vdWH is a promising noble-metal-free direct Z-scheme photocatalyst.

15.
Phys Chem Chem Phys ; 23(3): 2475-2482, 2021 Jan 28.
Artículo en Inglés | MEDLINE | ID: mdl-33463646

RESUMEN

Two-dimensional (2D) materials have attracted great interest in the field of optoelectronics in recent years due to their atomically thin structure and various electronic properties. Based on the first-principles calculations combined with the non-equilibrium Green's function (NEGF) method, we predict a set of new 2D ternary materials, sodium copper chalcogenides (NaCuX, X = S, Se, and Te). These materials not only have direct band gaps ranging from 1.2 to 1.6 eV, but also possess relatively small carrier effective masses (0.1-0.2m0) at the band edges thus high carrier mobilities (103-104 cm2 V-1 s-1), which collectively imply that they are suitable for optical-electronic applications in the visible (even in the infrared) light region. Moreover, based on the high photo responsivity (Rph), e.g., up to 0.105 A W-1 for NaCuTe, we design a series of NaCuX monolayer based high performance optoelectronic junctions. These properties indicate that NaCuX monolayers are promising candidate materials for photodetectors and photovoltaic units.

16.
Phys Chem Chem Phys ; 22(39): 22520-22528, 2020 Oct 15.
Artículo en Inglés | MEDLINE | ID: mdl-33000812

RESUMEN

A carbon phosphide (CP) monolayer, a 2D structure derived from the same 3-fold coordination found both in graphene and phosphorene, has been successfully synthesized in an experiment recently. In this paper, we investigated the modulation of electronic structures and transport characteristics of 2D nanosheets and quasi-1D nanoribbons of CP nanomaterials in the α-phase by using first-principles density functional theory simulation. The calculated band structures show that the band gap of 2D CP nanosheets progressively increases as the uniform biaxial strain changes from compression to stretching. However, the biaxial strain cannot change the indirect band gap behavior of the original 2D CP nanosheet. In addition, the band structures of quasi-1D nanoribbons with different styles of H-passivated zigzag edges have also been studied. The results show that the H-passivated zigzag PC ribbons with two P edges are semiconductors with indirect band gaps, and the gaps decrease with increasing width of ribbons. However, the H-passivated CP nanoribbons with one P-atom terminated edge in combination with one P-atom edge, and H-passivated CC nanoribbons with two C-atom terminated edges display metallic behaviors. The semi-conductive or metallic behaviors of zigzag CP nanoribbons can be explained by presenting the wave function of their energy band around the Fermi level. Finally, the electronic transport properties of different CP nanoribbon based nanojunctions are studied in which arise the interesting negative differential resistance or rectification effects in their current-voltage characteristic curves.

17.
Phys Chem Chem Phys ; 22(45): 26255-26264, 2020 Nov 25.
Artículo en Inglés | MEDLINE | ID: mdl-33174548

RESUMEN

We report an effective strategy for improving the electronic transport and switching behaviors of dimethyldihydropyrene/cyclophanediene (DHP/CPD)-based molecular devices, an intriguing photoswitch that can be triggered by ultraviolet/visible (UV-vis) light irradiation. Aiming to obtain molecular devices with high on-off ratios, we assess a series of molecular designs formed by [e]-fusing different arenes on a conjugated macrocycle to modulate the photochemical and electronic properties. Here, the switching mechanism and transport properties of [e]-fused DHP/CPD-based nanojunctions are theoretically investigated by first-principles calculations. As a result, the large diversity in electrical conductance between the closed and open forms certifies the substantial switching behavior observed in these sandwich structures. The maximum on-off ratios in all designed photoswitches are greater than 102. Further analysis confirms the improvement of switching performance caused by [e]-fusion. Notably, in the benzo-fused molecular junctions, the maximum on-off ratio is up to 103, which is 55 times larger than that of the un-fused one. We also find that the position of the switch core can remarkably affect the performance of photoswichable nanodevices.

18.
J Phys Chem A ; 124(51): 10678-10686, 2020 Dec 24.
Artículo en Inglés | MEDLINE | ID: mdl-33302627

RESUMEN

The aliphatic Claisen rearrangement of allyl vinyl ether has attracted great interest for its broad applications in chemical synthesis and biosynthesis. Although it is well agreed that this reaction proceeds via a concerted, "chair-like" transition state, certain inconsistencies of kinetic isotope effect (KIE) data between experimental measurements and theoretical simulations or between independent experiments indicate that the nature and mechanism of this important reaction need to be investigated in more detail. In order to verify two independent sets of experimental data, we present theoretical calculations on heavy-atom KIE values of alipahtic Claisen rearrangement, using our recently developed path-integral method with the second-order Kleinert's variational perturbation theory, which goes beyond the traditional method for computing KIE values by employing the Bigeleisen equation. Amazingly, the results demonstrate that both sets of experimental measurements are correct, while the inconsistency originates from the fact that the aliphatic Claisen rearrangement undergoes similar but different mechanisms in gas and solution phases. Different experimental conditions will alter the actual reactant state by tuning the population distribution of reactant conformers. According to the comparison between experimental and theoretical results, a more clear reaction mechanism of aliphatic Claisen rearrangement is revealed.

19.
Toxicol Appl Pharmacol ; 366: 1-9, 2019 03 01.
Artículo en Inglés | MEDLINE | ID: mdl-30660475

RESUMEN

Peniciketal A (Pe-A), a spiroketal compound, is isolated from the saline soil-derived fungus Penicillium raistrickii. However, the underlying molecular mechanistic basis for the effects of Pe-A on leukemia is poorly understood. Here, we investigated that Pe-A reduced cell proliferation in three leukemia cell lines (THP-1, K562 and HL60). Importantly, Pe-A showed little cytotoxicity in primary mouse embryonic fibroblast (MEF) cells in a long-duration treatment. For the mechanistic research, we identified 3449 differentially expressed Pe-A-induced proteins through liquid chromatography-tandem mass spectrometry (LC-MS/MS) with TMT label in THP-1 cells. Results showed that many identified proteins were involved in apoptosis and/or autophagy. Then, we confirmed that Pe-A induced not only apoptosis via the mitochondrial pathway but also cytoprotective autophagy by activating the AMP-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) signaling pathway indeed. In addition, Pe-A also arrested the cell cycle at the G0-G1 phase by regulating the expressions of checkpoint protein. Collectively, these results provide new insights into the mechanisms that Pe-A may target autophagy-related or apoptosis-related pathways to suppress the development of human leukemia.


Asunto(s)
Antineoplásicos/farmacología , Proliferación Celular , Leucemia/tratamiento farmacológico , Piranos/farmacología , Compuestos de Espiro/farmacología , Proteínas Quinasas Activadas por AMP/metabolismo , Animales , Antineoplásicos/toxicidad , Apoptosis/efectos de los fármacos , Proteínas Reguladoras de la Apoptosis/metabolismo , Autofagia/efectos de los fármacos , Proteínas Relacionadas con la Autofagia/metabolismo , Puntos de Control del Ciclo Celular/efectos de los fármacos , Cromatografía Líquida de Alta Presión , Células HL-60 , Humanos , Células K562 , Leucemia/metabolismo , Leucemia/patología , Ratones , Proteómica/métodos , Piranos/toxicidad , Transducción de Señal/efectos de los fármacos , Compuestos de Espiro/toxicidad , Células THP-1 , Serina-Treonina Quinasas TOR/metabolismo , Espectrometría de Masas en Tándem
20.
Anal Biochem ; 581: 113340, 2019 09 15.
Artículo en Inglés | MEDLINE | ID: mdl-31226253

RESUMEN

Colorectal cancer (CRC) is the third most common cancer worldwide. To date, no non-invasive and specific biomarkers have been identified for the diagnosis of CRC. The analysis of volatile organic compounds (VOCs) is attracting increasing attention and provides the possibility of a non-invasive diagnosis. Solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS) have been used to analyze the VOCs released from the headspace gas of LS174T (Dukes' type B colorectal adenocarcinoma) cells, arsenic trioxide (ATO)-treated LS174T cells and the blood from tumor-bearing mice. The data were processed using principal component analysis (PCA) and orthogonal partial least-squares discriminant analysis (OPLS-DA), which showed that the levels of decanal, 2,4-dimethyl- heptane, and twelve other metabolites were significantly greater in the headspace gas of the LS174T cells and blood of tumor-bearing mice. Additionally, in vivo experiments indicated that formic acid, ethenyl ester and p-trimethylsilyloxyphenyl-(trimethylsilyloxy)trimethylsilylacrylate were consumed during tumor growth. In conclusion, VOCs such as 1-methoxy-hexane and 2,4-dimethyl-heptane could be useful diagnostic markers for CRC. Further research should focus on the potential metabolic pathways associated with these profiles.


Asunto(s)
Neoplasias Colorrectales/metabolismo , Compuestos Orgánicos Volátiles/metabolismo , Animales , Trióxido de Arsénico/farmacología , Línea Celular Tumoral , Neoplasias Colorrectales/tratamiento farmacológico , Neoplasias Colorrectales/patología , Femenino , Cromatografía de Gases y Espectrometría de Masas , Humanos , Ratones Endogámicos BALB C , Ratones Desnudos , Compuestos Orgánicos Volátiles/análisis
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