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1.
Artigo em Inglês | MEDLINE | ID: mdl-38231805

RESUMO

Breast cancer, the predominant malignancy among women, is characterized by significant heterogeneity, leading to the emergence of distinct molecular subtypes. Accurate differentiation of these molecular subtypes holds paramount clinical significance, owing to substantial variations in prognosis, therapeutic strategies, and survival outcomes. In this study, we propose a cross-sequence joint representation and hypergraph convolution network (CORONet) for classifying molecular subtypes of breast cancer using incomplete DCE-MRI. Specifically, we first build a cross-sequence joint representation (COR) module to integrate image imputation and feature representation into a unified framework, encouraging effective feature extraction for subsequent classification. Then, we fuse multiple COR features and applied feature selection to reduce the redundant information between sequences. Finally, we deploy hypergraph structures to model high-order correlation among different subjects and extracted high-level semantic features by hypergraph convolutions for molecular subtyping. Extensive experiments on incomplete DCE-MRIs of 395 patients from the TCIA repository showed a significant improvement of our CORONet over state of the arts, with the area under the curve (AUC) of 0.891 and 0.903 for luminal and triple-negative (TN) subtype prediction, respectively. Similar advantages of CORONet were also confirmed in partial complete DCE-MRIs of 144 patients, achieving an AUC of 0.858 and 0.832 for predicting luminal and TN subtypes of breast cancer, respectively. Nevertheless, both of these values were lower compared to the scenario where DCE-MRIs from all 395 patients were utilized. Our study contributes to the precise molecular subtyping using incomplete multi-sequence DCE-MRI, thereby offering promising prospects for future risk stratification of breast cancer patients.

2.
ACS Cent Sci ; 9(2): 159-165, 2023 Feb 22.
Artigo em Inglês | MEDLINE | ID: mdl-36844489

RESUMO

Lignin-derived aromatic chemicals offer a compelling alternative to petrochemical feedstocks, and new applications are the focus of extensive interest. 4-Hydroxybenzoic acid (H), vanillic acid (G), and syringic acid (S) are readily obtained via oxidative depolymerization of hardwood lignin substrates. Here, we explore the use of these compounds to access biaryl dicarboxylate esters that represent biobased, less toxic alternatives to phthalate plasticizers. Chemical and electrochemical methods are developed for catalytic reductive coupling of sulfonate derivatives of H, G, and S to access all possible homo- and cross-coupling products. A conventional NiCl2/bipyridine catalyst is able to access the H-H and G-G products, but new catalysts are identified to afford the more challenging coupling products, including a NiCl2/bisphosphine catalyst for S-S and a NiCl2/phenanthroline/PdCl2/phosphine cocatalyst system for H-G, H-S, and G-S. High-throughput experimentation methods with a chemical reductant (Zn powder) are shown to provide an efficient screening platform for identification of new catalysts, while electrochemical methods can access improved yields and/or facilitate implementation on larger scale. Plasticizer tests are performed with poly(vinyl chloride), using esters of the 4,4'-biaryl dicarboxylate products. The H-G and G-G derivatives, in particular, exhibit performance advantages relative to an established petroleum-based phthalate ester plasticizer.

3.
Food Sci Nutr ; 11(1): 344-349, 2023 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-36655094

RESUMO

Liver fibrosis and cirrhosis are primarily caused by the activation of hepatic stellate cells (HSCs), regardless of their etiology. Collagen type I (collagen I) and connective tissue growth factor (CTGF) is produced more readily by activated HSCs. Consequently, identifying the molecular and cellular mechanisms responsible for HSCs activation is essential to better understand its mechanism of action and therapeutic potential. Cell death is caused by iron-dependent lipid peroxidation during ferroptosis. Ferroptosis plays an important role in the survival of activated HSCs and could contribute to the development of innovative prevention and treatment strategies for liver fibrosis. Danshensu (Dan) is a pure molecule extracted from the Salvia miltiorrhiza herb that protects against liver damage. However, Dan's effect on attenuating HSCs activation by regulating ferroptosis remains unclear. The results of this study indicated that lipopolysaccharide (LPS)-induced LX-2 and T6 cells activation occurs through the upregulation of collagen I, CTGF, Gpx4, and SLC7A11. Interestingly, Dan attenuated LPS-induced liver fibrosis in those cells by upregulating collagen I, CTGF, Gpx4, and SLC7A11 and by increasing lipid reactive oxygen species accumulation. Furthermore, the results also showed that the ferroptosis inhibitor liproxstatin attenuated the overproduction of lipid reactive oxygen species in LPS-activated LX-2 cells. We conclude that Dan attenuates LPS-induced HSC activation during liver fibrosis by regulating ferroptosis in LX-2 and T6 cells.

4.
J Am Chem Soc ; 144(49): 22641-22650, 2022 12 14.
Artigo em Inglês | MEDLINE | ID: mdl-36451553

RESUMO

Paired electrolysis methods are appealing for chemical synthesis because they generate valuable products at both electrodes; however, development of such reactions is complicated by the need for both half-reactions to proceed under mutually compatible conditions. Here, a modular electrochemical synthesis (ModES) strategy bypasses these constraints using a "redox reservoir" (RR) to pair electrochemical half-reactions across aqueous and nonaqueous solvents. Electrochemical oxidation reactions in organic solvents, the conversion of 4-t-butyltoluene to benzylic dimethyl acetal and aldehyde in methanol or the oxidative C-H amination of naphthalene in acetonitrile, and the reduction of oxygen to hydrogen peroxide in water were paired using nickel hexacyanoferrate as an RR that can selectively store and release protons (and electrons) while serving as the counter electrode for these reactions. Selective proton transport through the RR is optimized and confirmed to enable the ion balance, and thus the successful pairing, between redox half-reactions that proceed with different rates, on different scales, and in different solvents (methanol, acetonitrile, and water).


Assuntos
Metanol , Água , Oxirredução , Eletrodos , Solventes , Prótons , Acetonitrilas
5.
Fish Shellfish Immunol ; 128: 474-483, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-35988710

RESUMO

The freshwater amphibious snail Oncomelania hupensis is the unique intermediate host of Schistosoma japonicum, but little attention has been paid to the interaction between the two. In snails, the production of reactive oxygen species (ROS) by hemocytes has been shown to be vital for snail immune defense against schistosome infection. However, excessive ROS accumulation could lead to oxidative damage, requiring the antioxidant system for maintaining the cellular redox homeostasis. Previously we identified a thioredoxin-related protein of 14 kDa from O. hupensis (OhTRP14), and showed that it was involved in the scavenging of ROS in circulating hemocytes. Here, we confirmed that OhTRP14 plays a potential role in the snail host response to parasite challenge and determined the crystal structures of OhTRP14 in two different states (oxidized and transition state). The overall structure revealed a typical Trx fold and is similar to that of human TRP14 (hTRP14), but there were significant structural differences between the two states. Noticeably, there was a different pair of thiol groups from Cys30 and Cys44 in the transition state of OhTRP14, were with the similar separation of 2.9 Å as that (2.6 Å) between Cys41 and Cys44, but in a different orientation, suggesting that the Cys30 is likely to function as an important molecular switch involved in the oxidoreductase activity of OhTRP14. Comparative studies between OhTRP14 and hTRP14 by analyzing the surface characteristics, charge distribution and oxidoreductase activity toward insulin demonstrated they might have similar substrates. The results are expected to provide structural insights into the redox regulation of OhTRP14 and contribute to better understanding of TRP14 family. DATA DEPOSITION: The atomic coordinates of the structure and the structure factors were deposited in Protein Data Bank with PDB ID codes 7XQ3 and 7XPW.


Assuntos
Insulinas , Parasitos , Animais , Antioxidantes , China , Humanos , Oxirredução , Oxirredutases , Espécies Reativas de Oxigênio , Caramujos , Compostos de Sulfidrila , Tiorredoxinas/genética
6.
Acta Trop ; 234: 106615, 2022 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-35901919

RESUMO

Trichinella spiralis is a very successful parasite capable of surviving in many mammal hosts and residing in muscle tissues for long periods, indicating that it must have some effective strategies to escape from or guard against the host immune attack. The functions of MIF have been studied in other parasites and demonstrated to function as a virulence factor aiding in their survival by modulating the host immune response. However, the functions of Trichinella spiralis MIF (TsMIF) have not been addressed. Here, we successfully obtained the purified recombinant TsMIF and anti-TsMIF serum. Our results showed that TsMIF was expressed in all the Trichinella spiralis developmental stages, especially highly expressed in the muscle larvae (ML) and mainly located in stichocytes, midgut, cuticle, muscle cells of ML and around intrauterine embryos of female adults. We also observed TsMIF could be secreted from ML and bind to host monocytes. Next, our data demonstrated that TsMIF not only stimulated the phosphorylation of ERK1/2 and cell proliferation by binding to the host cell surface receptor CD74, but also interacted with a host intracellular protein, Jab1, which is a coactivator of AP-1 transcription. We concluded the secreted TsMIF plays an important role in the interaction between Trichinella spiralis and its host and could be a potential drug or vaccine target molecule against Trichinella spiralis infection.


Assuntos
Trichinella spiralis , Triquinelose , Vacinas , Animais , Feminino , Larva , Mamíferos , Monócitos , Trichinella spiralis/genética , Triquinelose/parasitologia
7.
Polymers (Basel) ; 14(4)2022 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-35215590

RESUMO

In the process of injection molding, a certain percentage of recycled material is usually used in order to save costs. The material properties of recycled materials can change significantly compared with raw materials, and the quality of their molded products is more difficult to control. Therefore, it is crucial to propose a method that can effectively maintain the yield of the recycled material products. In addition, the variation of clamping force during the injection molding process can be determined by measuring the tie-bar elongation of the injection molding machine. Therefore, this study proposes a real-time product quality monitoring system based on the variation of clamping force during the injection molding process for the injection molding of recycled materials for plastic bottle caps. The variation of clamping force reflects the variation of cavity pressure during the injection molding process and further maps the variation of injection parameters during the injection molding process. Therefore, this study evaluates the reliability of the proposed method for three different injection parameters (residual position, metering end point and metering time). Experiments have shown that there is a strong correlation between the quality (geometric properties) and weight of the product under different molding parameters. Moreover, the three main injection parameters have a strong influence on the weight and quality of the plastic caps. The variation of the clamping force is also highly correlated with the weight of the plastic bottle cap. This demonstrates the feasibility of applying the variation of clamping force to monitor the quality of injection molded products. Furthermore, by integrating the clamping force variation index with the calibration model of the corresponding injection parameters, it is possible to control the weight of the plastic cap within the acceptable range of the product in successive production runs.

9.
Front Surg ; 9: 1050347, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36895848

RESUMO

Purpose: To determine the incidence and risk factors of deep vein thrombosis (DVT) of lower extremities at admission in elderly Chinese patients with femoral neck fracture, and to establish and evaluate a new DVT predictor based on these risk factors. Methods: Patients who were hospitalized from January 2018 to December 2020 at three independent centers were reviewed. According to the results of lower extremities vascular ultrasound at admission, they were divided into DVT group and non-DVT group. Single and multivariate logistic regression analysis were applied to identify independent risk factors for DVT occurrence, and then a prediction formula for DVT based on the risk factors was developed. The new predictive index of DVT was calculated by the formula. Receiver operating characteristic (ROC) curve analysis was used to determine the diagnostic value of different factors and the new predictive index. Results: There were 203 elder patients were included in the final analysis after application of the exclusion criteria. Thirty seven patients (18.2%) were diagnosed as DVT by ultrasound, including 33 patients (89.2%) of peripheral type, 1 patient (2.7%) of central type and 3 patients (8.1%) of mixed type.Multivariate logistic regression analysis showed that four factors including injured side, hemoglobin, fibrinogen, d-dimer were the independent risk factors for the incidence of DVT. On this basis, a new formula for DVT predictive factor was constructed: New predictive index = 0.895 * injured side (right = 1, left = 0) + 0.899 * hemoglobin (<109.5 g/L = 1, > 109.5 g/L = 0) + 1.19 * fibrinogen (>4.24 g/L = 1, < 4.24 g/L = 0) + 1.221* d-dimer (>2.4 mg/L = 1, < 2.4 mg/L = 0). The AUC value of this new developed index was 0.735. Conclusions: This work showed that the incidence of DVT in elderly patients with femoral neck fracture in China was high at admission. New DVT predictive value can be used as an effective diagnosis strategy for evaluation of thrombosis at admission.

10.
J Clin Lab Anal ; 35(9): e23912, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34296781

RESUMO

BACKGROUND: Lung cancer is one of the most common malignancies, and there is a trend of increasing incidence in young patients. The preoperative diagnosis of pulmonary nodules is mainly based on the combination of imaging and tumor markers. There is no relevant report on the diagnostic value of tumor markers in young pulmonary nodules. Our study was designed to explore the value of five tumor markers in young patients with pulmonary nodules. METHODS: We reviewed the medical records of 390 young patients (age ≤45 years) with pulmonary nodules treated at two separate centers from January 1, 2015, to January 1, 2021. Malignant pulmonary nodules were confirmed in 318 patients, and the other 72 patients were diagnosed with benign pulmonary nodules. The gold standard for diagnosis of pulmonary nodules was surgical biopsy. The conventional serum biomarkers included cytokeratin 19 (CYFRA21-1), pro-gastrin-releasing-peptide (ProGRP), carcinoembryonic antigen (CEA), neuron-specific enolase (NSE), and squamous cell carcinoma-associated antigen (SCCA). The diagnostic values of five tumor markers were analyzed by receiver operating characteristic (ROC) curves. RESULTS: There were no significant differences in the expression of five tumor markers between the groups (p > 0.05). Single tumor marker (CYFRA21-1, ProGRP, CEA, NSE, and SCCA) showed a limited value in the diagnosis of malignant pulmonary nodules, with the AUC of 0.506, 0.503 0.532, 0.548, and 0.562, respectively. The AUC of the combined examination was only 0.502~0.596, which did not improve the diagnostic value. CONCLUSIONS: Five conventional tumor markers had a limited diagnostic value in young patients with pulmonary nodules.


Assuntos
Biomarcadores Tumorais/sangue , Neoplasias Pulmonares/diagnóstico , Nódulos Pulmonares Múltiplos/diagnóstico , Nódulo Pulmonar Solitário/diagnóstico , Adulto , Antígenos de Neoplasias/sangue , Antígeno Carcinoembrionário/sangue , Diagnóstico Diferencial , Feminino , Seguimentos , Proteínas Ligadas por GPI/sangue , Humanos , Queratina-19/sangue , Neoplasias Pulmonares/sangue , Neoplasias Pulmonares/cirurgia , Masculino , Pessoa de Meia-Idade , Nódulos Pulmonares Múltiplos/sangue , Nódulos Pulmonares Múltiplos/cirurgia , Fragmentos de Peptídeos/sangue , Fosfopiruvato Hidratase/sangue , Prognóstico , Curva ROC , Proteínas Recombinantes/sangue , Estudos Retrospectivos , Serpinas/sangue , Nódulo Pulmonar Solitário/sangue , Nódulo Pulmonar Solitário/cirurgia
11.
Acta Trop ; 211: 105623, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32645302

RESUMO

Oncomelania hupensis is the obligate intermediate host of Schistosoma japonicum, and it also serves as the first intermediate host for Exorchis sp., which uses Parasilurus asoyus as its definitive host rather than humans. In previous studies, Tang et al. found that all S. japonicum larvae can be blocked and killed in O. hupensis pre-infected with Exorchis sp. eggs. However, the molecular and cellular mechanisms involved in this process remain unclear. Therefore, in the present study, a combined transcriptomic and proteomic analysis was performed to identify the differential proteins involved in the immune response to the parasite S. japonicum in the O. hupensis snail host pre-infected with Exorchis sp. trematodes. The results showed that a total of 46,162 unigenes were obtained with 23,535 (50.98%) unigenes annotated in relevant databases, and 3811 proteins from O. hupensis were identified. In addition, iTRAQ-based quantitative proteomic analysis demonstrated that among three groups (OhSj-1_vs_OhN-1, OhE-1_vs_OhN-1 and OhES-1_vs_OhN-1), there were 146 common differential proteins including 44 up-regulated proteins and 90 down-regulated proteins, and 195 differential proteins exclusive to only one experimental group, including 91 up-regulated proteins and 104 down-regulated proteins, which were defined as the Common group and the Only group, respectively. KEGG analysis showed that 15 and 11 differential proteins were annotated in "Infectious diseases" in the Common group and the Only group, respectively, indicating that these proteins may be involved in the snail host immune response to parasite infection. These data will be helpful for better understanding the host-parasite interaction, and could pave the way towards exploring the mechanisms involved in the biological control on S. japonicum in O. hupensis. They also provide valuable information about developing new anti-schistosomiasis strategies.


Assuntos
Peixes-Gato/imunologia , Caramujos/imunologia , Caramujos/parasitologia , Transcriptoma/fisiologia , Animais , China , Interações Hospedeiro-Parasita , Humanos , Imunidade , Larva , Proteômica , Schistosoma japonicum
12.
Biochem J ; 477(12): 2133-2151, 2020 06 26.
Artigo em Inglês | MEDLINE | ID: mdl-32484230

RESUMO

Oncomelania hupensis is the unique intermediate host of Schistosoma japonicum. As an irreplaceable prerequisite in the transmission and prevalence of schistosomiasis japonica, an in-depth study of this obligate host-parasite interaction can provide glimpse into the molecular events in the competition between schistosome infectivity and snail immune resistance. In previous studies, we identified a macrophage migration inhibitory factor (MIF) from O. hupensis (OhMIF), and showed that it was involved in the snail host immune response to the parasite S. japonicum. Here, we determined the crystal structure of OhMIF and revealed that there were distinct structural differences between the mammalian and O. hupensis MIFs. Noticeably, there was a projecting and structured C-terminus in OhMIF, which not only regulated the MIF's thermostability but was also critical in the activation of its tautomerase activity. Comparative studies between OhMIF and human MIF (hMIF) by analyzing the tautomerase activity, oxidoreductase activity, thermostability, interaction with the receptor CD74 and activation of the ERK signaling pathway demonstrated the functional differences between hMIF and OhMIF. Our data shed a species-specific light on structural, functional, and immunological characteristics of OhMIF and enrich the knowledge on the MIF family.


Assuntos
Isomerases/metabolismo , Sistema de Sinalização das MAP Quinases , Fatores Inibidores da Migração de Macrófagos/química , Fatores Inibidores da Migração de Macrófagos/metabolismo , Caramujos/fisiologia , Sequência de Aminoácidos , Animais , Domínio Catalítico , Conformação Proteica , Homologia de Sequência , Especificidade por Substrato
13.
Bioorg Med Chem ; 28(12): 115551, 2020 06 15.
Artigo em Inglês | MEDLINE | ID: mdl-32503695

RESUMO

We describe here the design, synthesis, and evaluation of a macrocyclic peptidomimetic as a potent agent targeting enterovirus A71 (EV71). The compound has a 15-membered macrocyclic ring in a defined conformation. Yamaguchi esterification reaction was used to close the 15-membered macrocycle instead of the typical Ru-catalyzed ring-closing olefin metathesis reaction. The crystallographic characterization of the complex between this compound and its target, 3C protease from EV71, validated the design and paved the way for the generation of a new series of anti-EV71 agents.


Assuntos
Antivirais/síntese química , Desenho de Fármacos , Compostos Macrocíclicos/química , Proteases Virais 3C/química , Proteases Virais 3C/metabolismo , Animais , Antivirais/sangue , Antivirais/metabolismo , Antivirais/farmacologia , Sítios de Ligação , Catálise , Domínio Catalítico , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Cristalografia por Raios X , Estabilidade de Medicamentos , Enterovirus Humano A/efeitos dos fármacos , Enterovirus Humano A/enzimologia , Esterificação , Humanos , Compostos Macrocíclicos/sangue , Compostos Macrocíclicos/metabolismo , Compostos Macrocíclicos/farmacologia , Camundongos , Simulação de Dinâmica Molecular , Rutênio/química
14.
Cancer Biother Radiopharm ; 35(10): 753-759, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32379491

RESUMO

Background: FoxO3a is a well-studied tumor suppressor gene in the forkhead transcriptional factor O (FoxO) subfamily and its downregulation is correlated with the occurrence of gastric cancer (GC). GC tissues had microRNA (miR)-372 upregulation, which has targeted relationship with 3'-untranslated region (3'-UTR) of FoxO3a gene. This study investigated if miR-372 plays a role in modulating FoxO3a expression, and affecting GC cell proliferation, apoptosis, and cisplatin (DDP) resistance. Materials and Methods: Dual luciferase reporter gene assay assessed the targeted regulation between miR-372 and FoxO3a. DDP-resistant cell lines MGC803/DDP and MKN28/DDP were compared for gene expression against parental cells. Cell proliferation was measured by Cell Counting Kit-8 (CCK-8) assay. Cultured cells were transfected with miR-372 mimic or miR-negative control (NC) to measure FoxO3a mRNA and protein expression. Cell apoptosis and proliferation were tested by flow cytometry and 5-Ethynyl-2'-deoxyuridine (EdU) staining, respectively. Results: miR-372 had a targeted relationship with FoxO3a mRNA. MGC803/DDP and MKN28/DDP cells had significantly elevated miR-372 level than parental cells, while Foxo3a mRNA or protein levels were significantly decreased. CCK-8 assay revealed significantly lower inhibitory activity on cell proliferation in drug-resistant cells. Compared with miR-NC group, miR-273 inhibitor transfected DDP-resistant cells had significantly increased Foxo3a expression, enhanced cell apoptosis, reduced proliferation, and drug resistance. Conclusions: miR-372 upregulation is associated with DPP resistance of GC cells. Downregulation of miR-372 can inhibit proliferation, facilitate apoptosis, and suppress DDP resistance of drug-resistant GC cells.


Assuntos
Cisplatino/farmacologia , Proteína Forkhead Box O3/metabolismo , MicroRNAs/metabolismo , Neoplasias Gástricas/metabolismo , Antineoplásicos/farmacologia , Apoptose/fisiologia , Linhagem Celular Tumoral , Proliferação de Células/fisiologia , Resistencia a Medicamentos Antineoplásicos , Citometria de Fluxo , Proteína Forkhead Box O3/genética , Humanos , MicroRNAs/genética , Neoplasias Gástricas/tratamento farmacológico , Neoplasias Gástricas/genética , Neoplasias Gástricas/patologia , Transfecção , Regulação para Cima
15.
Materials (Basel) ; 13(5)2020 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-32150888

RESUMO

The purpose of this study is to clarify the influence of changes in glass fiber properties on warpage prediction, and to demonstrate the importance of accurate material property data in the numerical simulation of injection molding. In addition, this study proposes an optimization method based on the reverse warping agent model, in which the thermal conductivity of the plastic material is reduced, and the solidified layer on the surface of the mold is reduced and transferred from the molding material to the mold wall. This means that by the end of the cooling phase, the shrinkage of the molten zone within the component will continue, resulting in warpage. Based on the optimal process parameters, the sensitivity of the warpage prediction to the relationship between the two most important material properties, the glass fiber and holding pressure time, was analyzed. The material property model constants used for numerical simulations can sometimes vary significantly due to inherent experimental measurement errors, the resolution of the test device, or the manner in which the curve fit is performed to determine the model constants. This model has been developed to intelligently determine the preferred processing parameters and to gradually correct the details of the molding conditions. Thus, the cavity is separated in the critical warpage region, and a new cavity geometry with a reverse warped profile is placed into the mold base slot. The results show that the hypothetical and reasonable variation of the glass fiber model constant and the holding pressure time relationship may significantly affect the magnitude of the warpage prediction of glass fiber products. The greatest differences were found as a result of the warping orientation of the glass fiber material.

16.
Sci Rep ; 9(1): 5470, 2019 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-30940891

RESUMO

Generally, photon of Microwave (MW) electromagnetic waves have long been thought to be lower energy, which could not excite metals or semiconductor materials to generate electric current and electron-holes pairs (e-cb + h+vb). In this paper, we report an unexpected, Microwave "photoelectric effect", when MW irradiates on the semiconductor materials, leading to generate electric current and electron-holes pairs (e-cb + h+vb), on the semiconductor materials and on the MW catalyst. Further, we show that the action mechanism of Microwave "photoelectric effect" made water adsorbing on the surface of Microwave catalyst transform into hydroxyl radical (∙OH). Thus, this study has revealed the principle of generation Microwave "photoelectric effect" under MW irradiation, and the mechanism of MW catalytic oxidation degradation of organic in the wastewater and the mechanism of MW reduction method for preparation of nano-particle metal supported catalysts. Our findings challenge the classic view of MW irradiation only as heating method, which cannot excite to produce electric current and electron-holes pairs (e-cb + h+vb). Our findings will open new field to use MW technology for MW catalytic oxidation degradation of organics in the wastewater, and for MW reduction method of metal supported catalysts preparation.

17.
J Am Chem Soc ; 141(14): 5628-5634, 2019 04 10.
Artigo em Inglês | MEDLINE | ID: mdl-30888167

RESUMO

Annulated pyridines are ubiquitous scaffolds in many bioactive molecules. A highly regio- and enantioselective Ni(0)-catalyzed endo-selective C-H cyclization of pyridines with alkenes has been developed. An unprecedented enantioselective C-H activation at pyridyl 3- or 4-positions was enabled by bulky chiral N-heterocyclic carbene ligands. This protocol provides expedient access to a series of optically active 5,6,7,8-tetrahydroquinolines and 5,6,7,8-tetrahydroisoquinolines, compounds otherwise accessed with difficulty, in moderate to high yields (up to 99% yield) and enantioselectivities (up to 99% ee). To our knowledge, this is the first example of enantioselective C-H cyclization of pyridines to chiral annulated products.

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