Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 345
Filtrar
Mais filtros










Intervalo de ano de publicação
1.
Artigo em Inglês | MEDLINE | ID: mdl-32424859

RESUMO

The chemical structures and topologies of the crosslinks in supramolecular networks play a crucial role in their properties and functions. Herein, we prepared a type of poly( N -isopropylacrylamide) (PNIPAAM)-based supramolecular networks crosslinked by emissive hexagonal metallacycles. The topological connections in these networks greatly affect their properties, as evidenced by their differences in absorption, emission, lower critical solution temperature, and modulus along with the variation of crosslinking densities. The integration of PNIPAAM and metallacycles in the networks benefits them improved bioavailability, making them serve as reagents for bacterial imaging and killing. This study provides a strategy to prepare cavity-crosslinked polymer networks for antibacterial applications.

3.
iScience ; 23(5): 101064, 2020 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-32380420

RESUMO

Fractals are a series of intricate patterns with aesthetic, mathematic, and philosophic significance. The Sierpinski triangles have been known for more than one hundred years, but only recently discrete shape-persistent low-generation (mainly ST-1) fractal supramolecules have been realized. Herein, we report a retro-assembly pathway to the nanometer-scale, supra-macromolecular second-generation Sierpinski triangle and its third-generation saturated counterpart (Pascal's triangle). These gigantic triangular assemblies are unambiguously confirmed by NMR, DOSY, ESI-MS, TWIM-MS, TEM, and AFM analyses. Notably, the dense-packed counterions of these discrete triangular architectures could further form supramolecular hydro-gels in water. This work not only provides a fundamental chemical pathway to explore various giant supramolecular constructs and further overcome the synthetic limitation of complicated molecular fractals, but also presents a new type of supramolecular hydro-gels with potential in controlled release applications.

4.
BMC Genomics ; 21(1): 357, 2020 May 12.
Artigo em Inglês | MEDLINE | ID: mdl-32398006

RESUMO

BACKGROUND: Fusarium ear rot (FER) caused by Fusarium verticillioides is a major disease of maize that reduces grain yield and quality globally. However, there have been few reports of major loci for FER were verified and cloned. RESULT: To gain a comprehensive understanding of the genetic basis of natural variation in FER resistance, a recombinant inbred lines (RIL) population and one panel of inbred lines were used to map quantitative trait loci (QTL) for resistance. As a result, a total of 10 QTL were identified by linkage mapping under four environments, which were located on six chromosomes and explained 1.0-7.1% of the phenotypic variation. Epistatic mapping detected four pairs of QTL that showed significant epistasis effects, explaining 2.1-3.0% of the phenotypic variation. Additionally, 18 single nucleotide polymorphisms (SNPs) were identified across the whole genome by genome-wide association study (GWAS) under five environments. Compared linkage and association mapping revealed five common intervals located on chromosomes 3, 4, and 5 associated with FER resistance, four of which were verified in different near-isogenic lines (NILs) populations. GWAS identified three candidate genes in these consistent intervals, which belonged to the Glutaredoxin protein family, actin-depolymerizing factors (ADFs), and AMP-binding proteins. In addition, two verified FER QTL regions were found consistent with Fusarium cob rot (FCR) and Fusarium seed rot (FSR). CONCLUSIONS: These results revealed that multi pathways were involved in FER resistance, which was a complex trait that was controlled by multiple genes with minor effects, and provided important QTL and genes, which could be used in molecular breeding for resistance.

5.
Chemistry ; 2020 May 19.
Artigo em Inglês | MEDLINE | ID: mdl-32428362

RESUMO

Theranostic agents, taking the advantages of both imaging and therapeutic functions, are expected to develop personalized medicine in which the therapeutic response can be real-time monitored. Herein, we prepared three metallacycles with pendent adamantane groups via coordination-driven self-assembly of Pt(II) ligands with anticancer activities and tetraphenylethylene derivatives with emission. ß-Cyclodextrin which shows good host-guest interactions with adamantane moieties was added to form amphiphilic supramolecular nanoparticles with the aim to enhance the aqueous solubilities and bioactivities of these metallacycles. Moreover, when rhodamine-modified ß-cyclodextrin was used as the carrier, the release of the metallacycles from the nanoparticles could be monitored in situ through the fluorescence changes due to the efficient fluorescence resonance energy transfer from the metallacycles to rhodamine-modified ß-cyclodextrin. In vitro and in vivo studies showed that these nanoparticles not only served as cell imaging contrast agents but also displayed improved anticancer activities, making them serve as potential candidates for cancer theranostics. This study provides a simple and efficient method to prepare theranostic agents via hierarchical supramolecular self-assembly, which will pave the way for image-guided cancer therapy, targeted cancer therapy and related biomedical field.

6.
J Am Chem Soc ; 2020 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-32311259

RESUMO

Coordination-driven self-assembly has been extensively employed to construct a variety of discrete structures as a bottom-up strategy. However, mechanistic understanding regarding whether self-assembly is under kinetic or thermodynamic control is less explored. To date, such mechanistic investigation has been limited to distinct, assembled structures. It still remains a formidable challenge to study the kinetic and thermodynamic behavior of self-assembly systems with multiple assembled isomers due to the lack of characterization methods. Herein, we use a stepwise strategy which combined self-recognition and self-assembly processes to construct giant metallo-supramolecules with 8 positional isomers in solution. With the help of ultrahigh-vacuum, low-temperature scanning tunneling microscopy and scanning tunneling spectroscopy, we were able to unambiguously differentiate 14 isomers on the substrate which correspond to 8 isomers in solution. Through measurement of 162 structures, the experimental probability of each isomer was obtained and compared with the theoretical probability. Such a comparison along with density functional theory (DFT) calculation suggested that although both kinetic and thermodynamic control existed in this self-assembly, the increased experimental probabilities of isomers compared to theoretical probabilities should be attributed to thermodynamic control.

7.
J Am Chem Soc ; 2020 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-32302108

RESUMO

The precise construction of the high-order mechanically interlocked molecules (MIMs) with well-defined topological arrangements of multiple mechanically interlocked units has been a great challenge. Herein, we present the first successful preparation of a new family of daisy chain dendrimers, in which the individual [c2]daisy chain rotaxane units serve as the branches of dendrimer skeleton. In particular, the third-generation daisy chain dendrimer with 21 [c2]daisy chain rotaxane moieties was realized, which might be among the most complicated discrete high-order MIMs comprised of multiple [c2]daisy chain rotaxane units. Interestingly, such unique topological arrangements of multiple stimuli-responsive [c2]daisy chain rotaxanes endowed the resultant daisy chain dendrimers controllable and reversible nanoscale dimension modulation through the collective and amplified extension/contraction of each [c2]daisy chain rotaxane branch upon the addition of acetate anions or DMSO molecules as external stimulus. Furthermore, on the basis of such an intriguing size switching feature of daisy chain dendrimers, dynamic composite polymer films were constructed through the incorporation of daisy chain dendrimers into polymer films, which could undergo fast, reversible, and controllable shape transformations when DMSO molecules were employed as stimulus. The successful merging of [c2]daisy chain rotaxanes and dendrimers described herein provides not only a brand-new type of high-order mechanically interlocked systems with well-defined topological arrangements of [c2]daisy chain rotaxanes, but also a successful and practical approach toward the construction of supramolecular dynamic materials.

8.
J Comput Biol ; 2020 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-32298601

RESUMO

Metabolic genes have been reported to act as crucial roles in tumor progression. Lung adenocarcinoma (LUAD) is one of the most common cancers worldwide. This study aimed to predict the potential mechanism and novel markers of metabolic signature in LUAD. The gene expression profiles and the clinical parameters were obtained from The Cancer Genome Atlas-Lung adenocarcinoma (TCGA-LUAD) and Gene Expression Omnibus data set (GSE72094). A total of 105 differentially expressed metabolic genes of intersect expression in TCGA-LUAD and GSE72094 were screened by R language. Univariate Cox regression model found 18 survival-related genes and then the least absolute shrinkage and selection operator model was successfully constructed. Six significant genes prognostic model was validated though independent prognosis analysis. The model revealed high values for prognostic biomarkers by time-dependent receiver operating characteristic (ROC) analysis, risk score, Heatmap, and nomogram. In addition, Gene Set Enrichment Analysis showed that multiplex metabolism pathways correlated with LUAD. Furthermore, we found the six genes aberrantly expressed in LUAD samples. Our study showed that metabolism pathways play important roles in LUAD progression. The six metabolic genes could predict potential prognostic and diagnostic biomarkers in LUAD.

9.
Artigo em Inglês, Espanhol | MEDLINE | ID: mdl-32278502

RESUMO

INTRODUCTION: To study the expression of defensin-5 (RD-5), soluble phospholipase A2 (sPLA2) and lysozyme in the intestine in a rat model of acute liver failure and its relationship with intestinal bacterial translocation (BT). PATIENTS AND METHODS: Sprague-Dawley (SD) rats were divided into two groups. The experimental group was divided into five subgroups according to the lapsing time after the model was established, which were designated accordingly as 8h, 16h, 24h, 48h, and 72h groups. Acute liver failure (ALF) model was induced by intraperitoneal injection of 10% d-galactosamine. The homogenates of mesenteric lymph nodes (MLNs), liver and spleen from each group were cultured in agar to determine the bacterial outgrowth. The mRNA expression of RD-5, sPLA2, lysozyme and the protein expression of sPLA2, lysozyme were determined. RESULTS: No bacteria grew in the organ cultures from the control group while experimental groups had positive cultures. Expression of the RD-5 and sPLA2 mRNA in the experimental groups gradually increased at early time points and peaked 16h after induction of ALF, then progressively decreased. The mRNA expression of lysozyme in the experimental group peaked at 8h after ALF induction, then progressively decreased. Similar results were obtained with Western blot and immunohistochemical staining. DISCUSSION: The immune barrier function of the ileal mucosa in the rat model of acute liver failure was compromised as demonstrated by the decreased expression of RD-5, sPLA2 and lysozyme in Paneth cells along with increased intestinal bacterial translocation.

10.
World J Urol ; 2020 Apr 19.
Artigo em Inglês | MEDLINE | ID: mdl-32307555

RESUMO

OBJECTIVE: To preliminarily study the characteristics of bacterial flora distribution in the urine of ureteral stent encrustation patients as well as the relation between Bacteroides and stent encrustation. METHODS: Patients undergoing ureteral stenting were included in the study and divided into encrustation group and non-encrustation group based on the condition of stent encrustation. The urine of patients was collected to undergo 16s DNA test to compare the bacterial flora distribution characteristics of the two groups. The bacterial genus with highest abundance in the urine of encrustation group was used for animal experiment. A rat model with a foreign body in the bladder was created, in which the rats were injected with the aforesaid bacterial genus. A control group injected with normal saline was also formed. The incidence of foreign body tube encrustation between the two groups was compared. RESULTS: The urine collected from the patients in encrustation group contained a variety of bacteria, while dominant bacteria genera included g_Lactobacillus (23.1%), g_Bacteroides (18.8%) and g_norank_Bacteroides (17.1%). While the urine from the non-encrustation group was less diverse in bacteria flora, as the major bacteria genera were g_Escherichia-Shigella (32.2%), g_Enterococcus (24.9%) and g_Pseudomonas (18.2%). Bacteroidetes in the encrustation group were significantly higher, therefore Bacteroides fragilis in this genus was adopted for animal experiment, resulting in a higher incidence of foreign body tube encrustation in the bladder among rats. CONCLUSION: The present study enriches our knowledge about ureteral stent encrustation and reveals that the target regulation of urine bacteria is worth further research and clinical application.

11.
Nat Chem ; 12(5): 468-474, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32284575

RESUMO

For the past three decades, the coordination-driven self-assembly of three-dimensional structures has undergone rapid progress; however, parallel efforts to create large discrete two-dimensional architectures-as opposed to polymers-have met with limited success. The synthesis of metallo-supramolecular systems with well-defined shapes and sizes in the range of 10-100 nm remains challenging. Here we report the construction of a series of giant supramolecular hexagonal grids, with diameters on the order of 20 nm and molecular weights greater than 65 kDa, through a combination of intra- and intermolecular metal-mediated self-assembly steps. The hexagonal intermediates and the resulting self-assembled grid architectures were imaged at submolecular resolution by scanning tunnelling microscopy. Characterization (including by scanning tunnelling spectroscopy) enabled the unambiguous atomic-scale determination of fourteen hexagonal grid isomers.

12.
Adv Mater ; 32(17): e1908475, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32173920

RESUMO

Mechanically guided, 3D assembly has attracted broad interests, owing to its compatibility with planar fabrication techniques and applicability to a diversity of geometries and length scales. Its further development requires the capability of on-demand reversible shape reconfigurations, desirable for many emerging applications (e.g., responsive metamaterials, soft robotics). Here, the design, fabrication, and modeling of soft electrothermal actuators based on laser-induced graphene (LIG) are reported and their applications in mechanically guided 3D assembly and human-soft actuators interaction are explored. Over 20 complex 3D architectures are fabricated, including reconfigurable structures that can reshape among three distinct geometries. Also, the structures capable of maintaining 3D shapes at room temperature without the need for any actuation are realized by fabricating LIG actuators at an elevated temperature. Finite element analysis can quantitatively capture key aspects that govern electrothermally controlled shape transformations, thereby providing a reliable tool for rapid design optimization. Furthermore, their applications are explored in human-soft actuators interaction, including elastic metamaterials with human gesture-controlled bandgap behaviors and soft robotic fingers which can measure electrocardiogram from humans in an on-demand fashion. Other demonstrations include artificial muscles, which can lift masses that are about 110 times of their weights and biomimetic frog tongues which can prey insects.

13.
J Am Chem Soc ; 2020 Mar 19.
Artigo em Inglês | MEDLINE | ID: mdl-32160466

RESUMO

Design and construction of new functionalized supramolecular coordination complexes (SCCs) via coordination-driven self-assembly strategy is highly important in supramolecular chemistry and materials science. Herein, we present a family of well-defined metallacycles decorated with mesogenic forklike dendrons through the strategy of coordination-driven self-assembly. Due to the existence of mesogenic forklike dendrons, the obtained metallacycles displayed the smectic A liquid crystal phase at room temperature while their precursors exhibited the rectangular columnar liquid crystal phase. Interestingly, by taking advantage of the electrostatic interactions between the positively charged metallacycle and the negatively charged heparin, the doping of heparin induced a significant change of the liquid-crystalline behaviors of metallacycles. More importantly, the prepared liquid-crystalline metallacycles could be further applied for holographic storage of colored images. Notably, the rhomboidal metallacycle and hexagonal metallacycle gave rise to different holographic performances although they featured a similar liquid crystal phase behavior. Therefore, this research not only provides the first successful example of supramolecular liquid-crystalline metallacycles for holographic storage of colored images but also opens a new door for supramolecular liquid-crystalline metallacycles toward advanced optical applications.

14.
Biomed Res Int ; 2020: 8701759, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32185222

RESUMO

Objectives: To access the distinct values of contrast transcranial Doppler (cTCD), contrast transthoracic echocardiography (cTTE), and contrast transesophageal echocardiography (cTEE) in the diagnosis of right-to-left shunt (RLS) due to patent foramen ovale (PFO) and to define the most practical strategy for the diagnosis of PFO. Methods: 102 patients with a high clinical suspicion for PFO had simultaneous cTCD, cTTE, and cTEE performed. The agitated saline mixed with blood was used to detect right-to-left shunt (RLS). Results: In all 102 patients, the shunt was detected at rest by cTCD in 60.78% of cases, by cTTE in 42.16%, and by cTEE in 47.06%. The positive results of all 3 techniques with Valsalva maneuver (VM) were significantly improved. cTCD showed higher pick-up rate than cTTE (98.04% vs. 89.22%; χ 2 = 12.452, p < 0.05) and the cTEE (98.04% vs. 96.08%; nonsignificant difference) in the diagnosis of PFO. Nevertheless, cTEE, compared with cTTE, underestimated shunting in 44% of patients. The diameter of both PFO entrance and exit was significantly greater in patients with a severe shunt compared with a mild shunt (2.8 ± 1.0 mm vs. 2.0 ± 0.7 mm, t = 3.135, p < 0.05) and the cTEE (98.04% vs. 96.08%; nonsignificant difference) in the diagnosis of PFO. Nevertheless, cTEE, compared with cTTE, underestimated shunting in 44% of patients. The diameter of both PFO entrance and exit was significantly greater in patients with a severe shunt compared with a mild shunt (2.8 ± 1.0 mm vs. 2.0 ± 0.7 mm, t = 3.135, p < 0.05) and the cTEE (98.04% vs. 96.08%; nonsignificant difference) in the diagnosis of PFO. Nevertheless, cTEE, compared with cTTE, underestimated shunting in 44% of patients. The diameter of both PFO entrance and exit was significantly greater in patients with a severe shunt compared with a mild shunt (2.8 ± 1.0 mm vs. 2.0 ± 0.7 mm, t = 3.135, p < 0.05) and the cTEE (98.04% vs. 96.08%; nonsignificant difference) in the diagnosis of PFO. Nevertheless, cTEE, compared with cTTE, underestimated shunting in 44% of patients. The diameter of both PFO entrance and exit was significantly greater in patients with a severe shunt compared with a mild shunt (2.8 ± 1.0 mm vs. 2.0 ± 0.7 mm. Conclusions: The best method to diagnose PFO should be the combination of cTCD, cTTE, and cTEE. And cTCD should be applied as the first choice for screening RLS. Then, cTTE should be performed to quantify the severity of the shunt. Last but not least, cTEE should be performed to assess the morphologies of PFO when the closure is planned. The study provides for clinicians the most practical strategy for diagnosing PFO in the future. However, further trials with a large sample size are required to confirm this finding.

15.
J Am Chem Soc ; 142(13): 6196-6205, 2020 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-32150680

RESUMO

During the past few decades, the study of the single polymer chain has attracted considerable attention with the goal of exploring the structure-property relationship of polymers. It still, however, remains challenging due to the variability and low atomic resolution of the amorphous single polymer chain. Here, we demonstrated a new strategy to visualize the single metallopolymer chain with a hexameric or trimeric supramolecule as a repeat unit, in which Ru(II) with strong coordination and Fe(II) with weak coordination were combined together in a stepwise manner. With the help of ultrahigh-vacuum, low-temperature scanning tunneling microscopy (UHV-LT-STM) and scanning tunneling spectroscopy (STS), we were able to directly visualize both Ru(II) and Fe(II), which act as staining reagents on the repeat units, thus providing detailed structural information for the single polymer chain. As such, the direct visualization of the single random polymer chain is realized to enhance the characterization of polymers at the single-molecule level.

16.
Nurs Health Sci ; 2020 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-32141149

RESUMO

Factors affecting independence in basic and instrumental activities of daily living have been established in older adults, but not centenarians. The purpose of this study was to examine the state and factors affecting activities of daily living independence in centenarians who resided in Guangxi Province, China. A cross-sectional design was used. Activities of daily living, physical activity, mobility, and physical performance were measured by the Population Study of ChINese Elderly study instruments, and demographics and cognition were assessed. Of the 228 participants, 57% were independent in basic activities of daily living and 5.7% in instrumental activities of daily living. Stepwise regression showed physical activity, cognition, calf circumference, and self-reported health were associated with basic activities of daily living. Physical activity, mobility, cognition, and physical performance were correlated with instrumental activities of daily living. In conclusion, the Chinese centenarians showed impaired instrumental activities of daily living but mostly maintained basic functioning. Physical activity and cognition were associated with activities of daily living independence.

17.
Artigo em Inglês | MEDLINE | ID: mdl-32080962

RESUMO

Two rhomboidal metallacycles based on metal-coordination-driven self-assembly are presented. Because metal-coordination interactions restrict the rotation of phenyl groups on tetraphenylethene units, these metallacycles were emissive both in solution and in solid state, and their aggregation-induced emission properties were well-retained. Moreover, the rhomboidal metallacyclic structures offer a platform for intermolecular packing beneficial for the formation of liquid crystalline phases. Therefore, although neither of building blocks shows mesogenic properties, both thermotropic and lyotropic (in DMF) mesophases were observed in one of metallacycles, indicating that mesophases could be induced by metal-coordination interactions. This study not only reveals the mechanism for the formation of cavity-cored liquid crystals, but also provides a convenient approach to preparing supramolecular luminescent liquid crystals, which will serve as good candidates for chemo sensors and liquid crystal displays.

18.
Chem Commun (Camb) ; 56(20): 2987-2990, 2020 Mar 10.
Artigo em Inglês | MEDLINE | ID: mdl-32048633

RESUMO

The synergy among twelve carboxylates from two hexavalent baskets 16- assisted the encapsulation of one divalent diammonium guest 32+-62+ and the formation of ternary [3-6⊂12]10-. The reduction of basket's multivalency, by photoinduced α-decarboxylation of 16- to give 23-, intercepted the interannular cooperativity operating in the stabilization of capsulpex [3-6⊂12]10- to dramatically diminish the binding affinity towards diammonium guests. As a result, the cationic guests were released into bulk water with 23- assembling into nanoparticles. With numerous drugs carrying positive sites, the finding reported here could now be examined for their light-promoted spatiotemporal delivery.

19.
J Agric Food Chem ; 68(9): 2696-2701, 2020 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-32031789

RESUMO

All-cellulose composites are usually prepared by removing impurities and using a surface-selective dissolution approach, which detract significantly from their environment-friendly properties. In this paper, we report an environment-friendly approach to fabricate all-cellulose nanofiber composites from stack-up bacterial cellulose (BC) hydrogels via self-aggregation forces of the hydrogen bond by water-based processing. Structural and mechanical properties of BC-laminated composites have been investigated. The results indicated that BC composites possess the structure of all nanofibers, a tensile strength of 116 MPa, and a storage modulus of 25 GPa. Additionally, the interfacial shear strength and tensile strength of piece-hot-press BC demonstrate the strong self-aggregation forces of BC nanofibers. Thus, BC-laminated composites will be attractive in structural material.


Assuntos
Celulose/química , Gluconacetobacter xylinus/química , Hidrogéis/química , Nanofibras/química , Celulose/metabolismo , Gluconacetobacter xylinus/crescimento & desenvolvimento , Gluconacetobacter xylinus/metabolismo , Hidrogéis/metabolismo , Fenômenos Mecânicos , Resistência à Tração
20.
Artigo em Inglês | MEDLINE | ID: mdl-32077180

RESUMO

The fabrication of metal-supported hybrid structures with enhanced properties typically requires external energy input, such as pyrolysis, photolysis, and electrodeposition. In this study, silver-nanoparticle-decorated transition-metal hydroxide (TMH) composites were synthesized by an approach based on a spontaneous redox reaction (SRR) at room temperature. The SRR between silver ions and TMH provides a simple and facile route to establish effective and stable heterostructures that can enhance the oxygen evolution reaction (OER) activity. Ag@Co(OH)x grown on carbon cloth exhibits outstanding OER activity and durability, even superior to IrO2 and many previously reported OER electrocatalysts. Experimental and theoretical analysis demonstrates that the strong electronic interaction between Ag and Co(OH)2 activates the silver clusters as catalytically OER active sites, effectively optimizing the binding energies with reacted intermediates and facilitating the OER kinetics.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA