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1.
Org Biomol Chem ; 2020 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-32412573

RESUMO

Ergocytochalasin A (1), an unprecedented merocytochalasan formed via Diels-Alder cycloaddition of a cytochalasin with an ergosterol, was isolated from an endophytic fungus Phoma multirostrata XJ-2-1. Compound 1 possessed a unique 5/6/14/6/5/6/6/6 fused octacyclic ring system and its structure was established by detailed NMR and HRESIMS spectroscopic analyses. The absolute configuration of 1 was determined by single-crystal X-ray diffraction. A plausible biogenetic pathway of 1 was postulated. Compound 1 was evaluated for its cytotoxicity against six cancer cell lines and showed inhibitory effects with IC50 values ranging from 6.92 to 26.63 µM. The in vitro immunosuppressive activity of 1 against ConA-induced T cell and LPS-induced B cell proliferation, as well as its antiviral activity against Human dengue virus type 3 (DV3), influenza A virus (H1N1) and respiratory syncytial virus (RSV), was also evaluated. Ergocytochalasin A is the first example of a merocytochalasan which consists of one cytochalasin moiety and one ergosterol moiety. Containing eighteen chiral centers, ergocytochalasin A owns a folded framework, which makes it extremely compact in space.

2.
Nat Commun ; 11(1): 2309, 2020 May 08.
Artigo em Inglês | MEDLINE | ID: mdl-32385262

RESUMO

Electroluminescence of colloidal nanocrystals promises a new generation of high-performance and solution-processable light-emitting diodes. The operation of nanocrystal-based light-emitting diodes relies on the radiative recombination of electrically generated excitons. However, a fundamental question-how excitons are electrically generated in individual nanocrystals-remains unanswered. Here, we reveal a nanoscopic mechanism of sequential electron-hole injection for exciton generation in nanocrystal-based electroluminescent devices. To decipher the corresponding elementary processes, we develop electrically-pumped single-nanocrystal spectroscopy. While hole injection into neutral quantum dots is generally considered to be inefficient, we find that the intermediate negatively charged state of quantum dots triggers confinement-enhanced Coulomb interactions, which simultaneously accelerate hole injection and hinder excessive electron injection. In-situ/operando spectroscopy on state-of-the-art quantum-dot light-emitting diodes demonstrates that exciton generation at the ensemble level is consistent with the charge-confinement-enhanced sequential electron-hole injection mechanism probed at the single-nanocrystal level. Our findings provide a universal mechanism for enhancing charge balance in nanocrystal-based electroluminescent devices.

3.
Artigo em Inglês | MEDLINE | ID: mdl-32421230

RESUMO

This article offers a materials-chemistry perspective for colloidal quantum dots (QDs) in the field of display, including QD-enhanced liquid-crystal-display (QD-LCD) and QD-based light-emitting-diodes (QLEDs) display. The rapid successes of QDs for display in the past five years are not accidental but have a deep root in both maturity of their synthetic chemistry and their unique chemical, optical, and optoelectronic properties. This article intends to discuss the natural match of QD emitters for display and chemical means to eventually bring about their full potential.

4.
Exp Cell Res ; 391(1): 111975, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32229191

RESUMO

Transforming growth factor-ß-activated kinase 1 (TAK1)-binding protein 3 (TAB3) and the proviral integration site for Moloney murine leukaemia virus 1 (PIM1) are implicated in cancer development. In this study, we investigated the relationship between TAB3 and PIM1 in colorectal cancer (CRC) and determined the potential role and molecular mechanism of TAB3 in PIM1-mediated CRC growth. We found that TAB3 and PIM1 expression levels were positively correlated in CRC tissues. The knockdown of TAB3 significantly decreased PIM1 expression and inhibited CRC proliferation in vitro and in vivo. The upregulation of PIM1 rescued the decreased cell proliferation induced by TAB3 knockdown, whereas PIM1 knockdown decreased TAB3-enhanced CRC proliferation. Additionally, TAB3 regulates PIM1 expression through the STAT3 signalling pathway and confirmed a positive correlation between TAB3 and phosphorylated-STAT3 expression in CRC tissues. Patients with high expression of TAB3 and phosphorylated-STAT3 had the worst prognosis. Mechanistically, TAB3 regulates PIM1 expression by promoting STAT3 phosphorylation and activation through the formation of the TAB3-TAK1-STAT3 complex. Overall, a novel CRC regulatory circuit involving the TAB3-TAK1-STAT3 complex and PIM1 was identified, the dysfunction of which may contribute to CRC tumorigenesis.

5.
J Am Chem Soc ; 142(9): 4254-4264, 2020 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-32045520

RESUMO

By taking advantage of well-defined spectroscopic signatures of high-quality CdSe/CdS core/shell QDs, the effects of oxygen on photoluminescence (PL) of QDs were studied systematically and quantitatively at both single-dot and ensemble (on substrate and in solution) levels, which reveals a unified yet simple picture. With a sufficient amount of oxygen in the system during photoexcitation, the core/shell QDs in all forms would be deionized timely from the photogenerated and inefficient trion state back to the efficient single-exciton state, with superoxide radicals as the reduction product of oxygen. Under a given excitation power, rates of both spontaneous deionization and photodeionization channels increased by increasing the oxygen pressure, but photoionization of the QDs was barely affected by the oxygen pressure. While stabilizing PL by oxygen was identified for both CdSe plain core and CdSe/CdS core/shell QDs, irreversible photocorrosion was only observed for CdSe plain core QDs, suggesting the importance of high-quality epitaxial shells for QDs in various applications.

6.
Org Lett ; 22(3): 1071-1075, 2020 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-31939304

RESUMO

Incarnolides A (1) and B (2), two schinortriterpenoids (SNTs) featuring a tricyclo[9.2.1.02,8]tetradecane-bridged system, together with two biosynthetically related known SNTs, lancifonins A (3) and C (4), were isolated from the stems of Schisandra incarnata. Their structures were elucidated by extensive spectroscopic analyses, and the absolute configurations were assigned by single-crystal X-ray diffraction and electronic circular dichroism calculation. The hypothetical biogenetic pathway of 1 and 2 was postulated. Compound 1 exhibited antiviral and neuroprotective activities.

7.
Phytochemistry ; 170: 112201, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31778881

RESUMO

Nine undescribed triterpenoids (jughopenoids A-I), including seven nortriterpenoids and two normal triterpenoids, together with fourteen known analogues, were isolated from the barks of Juglans hopeiensis Hu. The structures of the undescribed triterpenoids were established by integrated spectroscopic analysis and single crystal X-ray diffraction. Jughopenoid A represented an unprecedented lupane-type nortriterpenoid with a five-membered lactone ring A. Selected isolates were tested for their cytotoxic effects against human HT-29 colon carcinoma, human HepG2 hepatocellular carcinoma, and human PC-3 prostate cancer cell lines. Their immunosuppressive activities against ConA-induced T cell proliferation and LPS-induced B cell proliferation were also evaluated.


Assuntos
Antineoplásicos Fitogênicos/farmacologia , Juglans/química , Compostos Fitoquímicos/farmacologia , Casca de Planta/química , Triterpenos/farmacologia , Antineoplásicos Fitogênicos/química , Antineoplásicos Fitogênicos/isolamento & purificação , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Cristalografia por Raios X , Relação Dose-Resposta a Droga , Ensaios de Seleção de Medicamentos Antitumorais , Células HT29 , Células Hep G2 , Humanos , Modelos Moleculares , Estrutura Molecular , Células PC-3 , Compostos Fitoquímicos/química , Compostos Fitoquímicos/isolamento & purificação , Relação Estrutura-Atividade , Triterpenos/química , Triterpenos/isolamento & purificação
8.
J Chem Phys ; 151(23): 234703, 2019 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-31864257

RESUMO

Auger nonradiative recombination dominates decay of multicarrier states in high quality colloidal quantum dots (QDs) and thus is critical for many of their optical and optoelectronic applications. Controlling interface-potential smoothness and wavefunction delocalization are proposed as two main strategies for Auger engineering in core/shell QDs. Here, a series of CdSe-based core/shell QDs with nearly ideal optical quality of their single-exciton states are developed and applied for studying biexciton quantum yields and Auger nonradiative recombination rates. Comparative experiments find that the interface-potential smoothness has little influence on biexciton quantum yield and Auger rates of these core/shell QDs with the same CdS outer shells. In contrast, with a fixed total size of the series of QDs, the decreasing hole wavefunction delocalization can increase the Auger rates of positive trions by ∼400%. A mild decrease in electron wavefunction delocalization among the series of QDs results in a small increase in the Auger rates of negative trions (∼50%). Smoothing the core/shell interface can indeed affect the Auger rates, but this is by the way of altering wavefunction delocalization. These findings highlight the importance of control of wavefunction delocalization among the strategies of Auger engineering and provide guidelines for rational design QDs for applications.

9.
J Am Chem Soc ; 141(44): 17617-17628, 2019 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-31610655

RESUMO

Wurtzite CdSe@CdS dot@platelet nanocrystals, dot-shaped CdSe nanocrystals encased within epitaxially grown CdS nanoplatelets, are controllably synthesized with nearly monodisperse size and shape distribution and outstanding photoluminescence (PL) properties. The excellent size and shape control with their lateral to thickness dimension ratio up to 3:1 is achieved by systematically studying the synthetic parameters, which results in a simple, tunable, yet reproducible epitaxy scheme. These special types of core/shell nanocrystals possess two-dimensional emission dipoles with the ab plane of the wurtzite structure. While their near-unity PL quantum yield and monoexponential PL decay dynamics are at the same level of the state-of-art CdSe/CdS core/shell nanocrystals in dot shape, CdSe@CdS dot@platelet nanocrystals possess ∼2 orders of magnitude lower probability for initiating PL blinking at the single-nanocrystal level than the dot-shaped counterparts do.

10.
Angew Chem Int Ed Engl ; 58(49): 17764-17770, 2019 Dec 02.
Artigo em Inglês | MEDLINE | ID: mdl-31591763

RESUMO

Facet-dependent on-surface reactions are systematically studied on zinc-blende CdSe nanoplatelets with atomically-flat {001} basal facets and small yet non-polar side facets. The on-surface half-reactions between the surface Se sites and Cd carboxylates in the solution are qualitatively equivalent to those on the spheroidal counterparts. Conversely, the on-surface half-reactions between the surface Cd sites and the activated Se precursors in solution show a strong facet-dependence, which includes three distinguishable stages. In the first stage, the Se precursors adsorb onto the small and non-polar side facets of the nanoplatelets. The second stage is initiated by the adsorbed Se precursors at the side-basal plane edges and proceeds from the edges to the center of the basal planes in quasi-zeroth-order kinetics. In the third stage, the nanoplatelets are dismantled, which includes the creation of a hole in the middle and a build-up of thick edges.

11.
J Am Chem Soc ; 141(39): 15675-15683, 2019 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-31503473

RESUMO

Aliphatic carboxylates are the most common class of surface ligands to stabilize colloidal nanocrystals. The widely used approach to identify the coordination modes between surface cationic sites and carboxylate ligands is based on the empirical infrared (IR) spectroscopic assignment, which is often ambiguous and thus hampers the practical control of surface structures. In this report, multiple techniques based on nuclear magnetic resonance (NMR) and IR spectra are applied to distinguish the different coordination structures in a series of zinc-blende CdSe nanocrystals with unique facet structures, including nanoplatelets dominated with {100} basal planes, hexahedrons with only three types of low-index facets (i.e., {100}, {110}, and {111}), and spheroidal dots without well-defined facets. Interpretation and assignment of NMR and IR signals were assisted by density functional theory (DFT) calculations. In addition to the identification of facet-sensitive bonding modes, the present methods also allow a nondestructive quantification of mixed ligands.

12.
Nat Commun ; 10(1): 3078, 2019 Jul 09.
Artigo em Inglês | MEDLINE | ID: mdl-31289268

RESUMO

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

13.
Nat Prod Res ; : 1-7, 2019 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-31328576

RESUMO

Three new phenolic compounds, 2,3,4-trihydroxy-1-(4'-hydroxybenzyl)benzoic acid (1), 2,3,4-trihydroxy-1-(4'-hydroxy-3'-methoxybenzyl)benzoic acid (2), and 2-(4'-hydroxy-3'-methoxybenzyl)-3,5-dimethoxy-1,4-benzoquinone (3), were isolated from the fresh pericarps of Juglans sigillata Dode. Their structures were elucidated by integrated spectroscopic techniques. Bioactivity screening results showed that compounds 1-3 exhibited moderate neuroprotective effects against H2O2-induced or CoCl2-induced cellular damage in human neuroblastoma SH-SY5Y cell line.

14.
Sci Adv ; 5(7): eaaw7935, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31355338

RESUMO

The transient receptor potential canonical subfamily member 5 (TRPC5), one of seven mammalian TRPC members, is a nonselective calcium-permeant cation channel. TRPC5 is of considerable interest as a drug target in the treatment of progressive kidney disease, depression, and anxiety. Here, we present the 2.8-Å resolution cryo-electron microscopy (cryo-EM) structure of the mouse TRPC5 (mTRPC5) homotetramer. Comparison of the TRPC5 structure to previously determined structures of other TRPC and TRP channels reveals differences in the extracellular pore domain and in the length of the S3 helix. The disulfide bond at the extracellular side of the pore and a preceding small loop are essential elements for its proper function. This high-resolution structure of mTRPC5, combined with electrophysiology and mutagenesis, provides insight into the lipid modulation and gating mechanisms of the TRPC family of ion channels.

15.
Nat Commun ; 10(1): 2454, 2019 06 05.
Artigo em Inglês | MEDLINE | ID: mdl-31165734

RESUMO

A typical colloidal nanoparticle can be viewed as a nanocrystal-ligands complex with an inorganic single-crystalline core, the nanocrystal, bonded with a monolayer of organic ligands. The surface chemistry of nanocrystal-ligands complexes is crucial to their bulk properties. However, deciphering the molecular pictures of the nonperiodic and dynamic organic-inorganic interlayer is a grand technical challenge, and this hampers the quantitative perception of their macroscopic phenomena. Here we show that the atomic arrangement on nanocrystal surface and ligand-ligand interactions can be precisely quantified through comprehensive solid-state nuclear magnetic resonance (SSNMR) methodologies. The analyses reveal that the mixed ligands of n-alkanoates on a CdSe nanocrystal segregate in areal partitions and the unique arrangement unlocks their rotational freedom. The mathematical model based on the NMR-derived ligand partition and dynamics successfully predicts the unusual solubility of nanocrystal-ligands complexes with mixed ligands, which is several orders of magnitude higher than that of nanocrystal-ligands complexes with pure ligands.

16.
Fitoterapia ; 136: 104165, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31075486

RESUMO

Ten new diarylheptanoids (1-10), including five diarylether-type (1-5), three biaryl-type (6-8), and two linear type (9-10), along with eighteen known ones, were isolated from the fresh pericarps of Juglans hopeiensis Hu. Their structures were settled by integrated spectroscopic techniques, and their absolute configurations were determined by a combination of circular dichroism analysis, optical rotations, and NOESY experiments. Screening results showed that some isolated diarylheptanoids exhibited moderate neuroprotective effects on H2O2-induced or CoCl2-induced cellular damage in human neuroblastoma SH-SY5Y cells.


Assuntos
Diarileptanoides/farmacologia , Juglans/química , Neuroblastoma/patologia , Fármacos Neuroprotetores/farmacologia , Linhagem Celular Tumoral , China , Diarileptanoides/isolamento & purificação , Humanos , Estrutura Molecular , Fármacos Neuroprotetores/isolamento & purificação , Compostos Fitoquímicos/isolamento & purificação , Compostos Fitoquímicos/farmacologia
17.
Nat Prod Res ; : 1-8, 2019 May 29.
Artigo em Inglês | MEDLINE | ID: mdl-31140329

RESUMO

Two new triterpenoids (1-2), jughopanes A (1) and jughopanes B (2), along with seventeen known ones (3-19), were isolated from the fresh pericarps of Juglans hopeiensis Hu. Their structures were settled by integrated spectroscopic techniques. All isolates were tested for their cytotoxic activities and the results showed that 7 exhibited moderate cytotoxicities against MCF7 and HT29 cancer cell lines with IC50 values of 5.24 and 6.01 µM, respectively.

18.
J Am Chem Soc ; 141(16): 6448-6452, 2019 Apr 24.
Artigo em Inglês | MEDLINE | ID: mdl-30964282

RESUMO

We introduce stoichiometry control within both core and shell regions of InP/ZnSe/ZnS core/shell/shell quantum dots (QDs) to advance their properties drastically, approaching those of state-of-the-art CdSe-based QDs. The resulting QDs possess near-unity photoluminescence quantum yield, monoexponential decay dynamics, narrow line width, and nonblinking at a single-dot level. Quantum-dot light-emitting diodes (QLEDs) with the InP/ZnSe/ZnS core/shell/shell QDs as emitters exhibit a peak external quantum efficiency of 12.2% and a maximum brightness of >10 000 cd m-2, greatly exceeding those of the Cd/Pb-free QLEDs reported in literature. These results pave the way toward Cd/Pb-free QDs as outstanding optical and optoelectronic materials.

19.
Nat Commun ; 10(1): 1750, 2019 04 15.
Artigo em Inglês | MEDLINE | ID: mdl-30988287

RESUMO

Auger recombination is the main non-radiative decay pathway for multi-carrier states of colloidal quantum dots, which affects performance of most of their optical and optoelectronic applications. Outstanding single-exciton properties of CdSe/CdS core/shell quantum dots enable us to simultaneously study the two basic types of Auger recombination channels-negative trion and positive trion channels. Though Auger rates of positive trion are regarded to be much faster than that of negative trion for II-VI quantum dots in literature, our experiments find the two rates can be inverted for certain core/shell geometries. This is confirmed by theoretical calculations as a result of geometry-dependent dielectric screening. By varying the core/shell geometry, both types of Auger rates can be independently tuned for ~ 1 order of magnitude. Experimental and theoretical findings shed new light on designing quantum dots with necessary Auger recombination characteristics for high-power light-emitting-diodes, lasers, single-molecular tracking, super-resolution microscope, and advanced quantum light sources.

20.
J Am Chem Soc ; 141(6): 2288-2298, 2019 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-30649864

RESUMO

Mn2+-doped ZnSe nanocrystals (Mn:ZnSe d-dots) with high optical quality-high dopant emission quantum yield with monoexponential dopant-emission decay dynamics-enable systematic and quantitative studies of temperature- and Mn2+ concentration-dependent optical properties of the dopant emission, especially its relationship with magnetic coupling. While temperature-dependent steady-state and transient dopant emission of d-dots with dilute Mn2+ concentrations originated from isolated Mn2+ ions, and can be quantitatively treated as a result of exciton-phonon coupling of isolated paramagnetic emission centers. Dopant emission of d-dots with high Mn2+ concentrations (up to 50% of Zn2+ ions being replaced by Mn2+ ions in the core nanocrystals) are found solely related to magnetically coupled Mn2+ emission. Magnetic coupling effects on steady-state dopant emission of d-dots with high Mn2+ concentrations are much stronger than those observed for doped bulk semiconductors, which is found to follow a strong and universe shell-thickness dependence for the epitaxial ZnSe and/or ZnS shells of the d-dots. By exciting the magnetically coupled Mn2+ ions directly, dopant-emission of d-dots with high Mn2+ concentrations exhibit monoexponential decay dynamics. In addition to this emission channel, a minor channel with slightly longer decay lifetime appears when the host nanocrystals with high Mn2+ concentrations are excited, which is barely visible at room temperature and increases its fraction by decreasing temperature.

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