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1.
Nature ; 582(7812): E13, 2020 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-32461696

RESUMEN

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

2.
Nature ; 582(7812): E14, 2020 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-32472016

RESUMEN

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

3.
Nature ; 566(7745): 480-485, 2019 02.
Artículo en Inglés | MEDLINE | ID: mdl-30814710

RESUMEN

Using a recently developed formalism called topological quantum chemistry, we perform a high-throughput search of 'high-quality' materials (for which the atomic positions and structure have been measured very accurately) in the Inorganic Crystal Structure Database in order to identify new topological phases. We develop codes to compute all characters of all symmetries of 26,938 stoichiometric materials, and find 3,307 topological insulators, 4,078 topological semimetals and no fragile phases. For these 7,385 materials we provide the electronic band structure, including some electronic properties (bandgap and number of electrons), symmetry indicators, and other topological information. Our results show that more than 27 per cent of all materials in nature are topological. We provide an open-source code that checks the topology of any material and allows other researchers to reproduce our results.

4.
J Am Chem Soc ; 146(6): 3890-3899, 2024 Feb 14.
Artículo en Inglés | MEDLINE | ID: mdl-38294957

RESUMEN

Topological insulators offer significant potential to revolutionize diverse fields driven by nontrivial manifestations of their topological electronic band structures. However, the realization of superior integration between exotic topological states and superconductivity for practical applications remains a challenge, necessitating a profound understanding of intricate mechanisms. Here, we report experimental observations for a novel superconducting phase in the pressurized second-order topological insulator candidate Ta2Pd3Te5, and the high-pressure phase maintains its original ambient pressure lattice symmetry up to 45 GPa. Our in situ high-pressure synchrotron X-ray diffraction, electrical transport, infrared reflectance, and Raman spectroscopy measurements, in combination with rigorous theoretical calculations, provide compelling evidence for the association between the superconducting behavior and the densified phase. The electronic state change around 20 GPa was found to modify the topology of the Fermi surface directly, which synergistically fosters the emergence of robust superconductivity. In-depth comprehension of the fascinating properties exhibited by the compressed Ta2Pd3Te5 phase is achieved, highlighting the extraordinary potential of topological insulators for exploring and investigating high-performance electronic advanced devices under extreme conditions.

5.
BMC Plant Biol ; 24(1): 555, 2024 Jun 14.
Artículo en Inglés | MEDLINE | ID: mdl-38877393

RESUMEN

BACKGROUND: Selenium is essential for livestock and human health. The traditional way of adding selenium to livestock diets has limitations, and there is a growing trend to provide livestock with a safe and efficient source of selenium through selenium-enriched pasture. Therefore, this study was conducted to investigate the effects of selenium enrichment on fermentation characteristics, selenium content, selenium morphology, microbial community and in vitro digestion of silage alfalfa by using unenriched (CK) and selenium-enriched (Se) alfalfa as raw material for silage. RESULTS: In this study, selenium enrichment significantly increased crude protein, soluble carbohydrate, total selenium, and organic selenium contents of alfalfa silage fresh and post-silage samples, and it significantly decreased neutral detergent fiber and acid detergent fiber contents (p < 0.05). Selenium enrichment altered the form of selenium in plants, mainly in the form of SeMet and SeMeCys, which were significantly higher than that of CK (p < 0.05). Selenium enrichment could significantly increase the lactic acid content, reduce the pH value, change the diversity of bacterial community, promote the growth of beneficial bacteria such as Lactiplantibacillus and inhibit the growth of harmful bacteria such as Pantoea, so as to improve the fermentation quality of silage. The in vitro digestibility of dry matter (IVDMD), in vitro digestibility of acid detergent fibers (IVADFD) and in vitro digestibility of acid detergent fibers (IVNDFD) of silage after selenium enrichment were significantly higher than those of CK (p < 0.05). CONCLUSION: This study showed that the presence of selenium could regulate the structure of the alfalfa silage bacterial community and improve alfalfa silage fermentation quality. Selenium enrichment measures can change the morphology of selenium in alfalfa silage products, thus promoting the conversion of organic selenium.


Asunto(s)
Fermentación , Medicago sativa , Microbiota , Selenio , Ensilaje , Medicago sativa/metabolismo , Ensilaje/análisis , Selenio/metabolismo , Animales , Alimentación Animal/análisis
6.
J Synchrotron Radiat ; 31(Pt 2): 378-384, 2024 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-38241124

RESUMEN

An integrated computer software system for macromolecular crystallography (MX) data collection at the BL02U1 and BL10U2 beamlines of the Shanghai Synchrotron Radiation Facility is described. The system, Finback, implements a set of features designed for the automated MX beamlines, and is marked with a user-friendly web-based graphical user interface (GUI) for interactive data collection. The Finback client GUI can run on modern browsers and has been developed using several modern web technologies including WebSocket, WebGL, WebWorker and WebAssembly. Finback supports multiple concurrent sessions, so on-site and remote users can access the beamline simultaneously. Finback also cooperates with the deployed experimental data and information management system, the relevant experimental parameters and results are automatically deposited to a database.

7.
Appl Environ Microbiol ; 90(2): e0145323, 2024 Feb 21.
Artículo en Inglés | MEDLINE | ID: mdl-38224623

RESUMEN

Polymetallic exposure causes complex toxicity to microorganisms. In this study, we investigated the responses of Escherichia coli under co-existence of cadmium (Cd) and lead (Pb), primarily based on biochemical analysis and RNA sequencing. Cd completely inhibited bacterial growth at a concentration of 2.41 mmol/L, with its removal rate as low as <10%. In contrast, the Pb removal rate was >95% under equimolar sole Pb stress. In addition, the Raman analysis confirmed the loss of proteins for the bacterial cells. Under the co-existence of Cd and Pb, the Cd toxicity to E. coli was alleviated. Meanwhile, the biosorption of Pb cations was more intense during the competitive sorption with Cd. Transmission electron microscopy images showed that a few cells were elongated during incubation, i.e., the average cellular length increased from 1.535 ± 0.407 to 1.845 ± 0.620 µm. Moreover, NanoSIMS imaging showed that the intracellular distribution of Cd and Pb was coupled with sulfur. Genes regulating sulfate transporter were also upregulated to promote sulfate assimilation. Then, the subsequent production of biogenic sulfide and sulfur-containing amino acids was enhanced. Although this strategy based on S enrichment could resist the polymetallic stress, not all related genes were induced to upregulate under sole Cd stress. Therefore, the S metabolism might remodel the microbial resistance to variable occurrence of heavy metals. Furthermore, the competitive sorption (in contrast to sole Cd stress) could prevent microbial cells from strong Cd toxicity.IMPORTANCEMicrobial tolerance and resistance to heavy metals have been widely studied under stress of single metals. However, the polymetallic exposure seems to prevail in the environment. Though microbial resistance can alleviate the effects of exogenous stress, the taxonomic or functional response to polymetallic exposure is still not fully understood. We determined the strong cytotoxicity of cadmium (Cd) on growth, and cell elongation would be driven by Cd stress. The addition of appropriate lead (Pb) showed a stimulating effect on microbial bioactivity. Meanwhile, the biosorption of Pb was more intense during co-existence of Pb and Cd. Our work also revealed the spatial coupling of intracellular S and Cd/Pb. In particular, the S assimilation was promoted by Pb stress. This work elucidated the microbial responses to polymetallic exposure and may provide new insights into the antagonistic function during metal stresses.


Asunto(s)
Metales Pesados , Contaminantes del Suelo , Cadmio/metabolismo , Plomo , Bioacumulación , Escherichia coli/genética , Escherichia coli/metabolismo , Metales Pesados/análisis , Azufre , Contaminantes del Suelo/metabolismo
8.
Langmuir ; 2024 Feb 06.
Artículo en Inglés | MEDLINE | ID: mdl-38320286

RESUMEN

All-inorganic perovskite solar cells (PSCs) have recently received increasing attention due to their outstanding thermal stability. However, the performance of these devices, especially for the devices with a p-i-n structure, is still inferior to that of the typical organic-inorganic counterparts. In this study, we introduce phenylammonium iodides with different side groups on the surface of the CsPbI2Br perovskite film and investigate their passivation effects. Our studies indicate that the 4-trifluoromethyl phenylammonium iodide (CFPA) molecule with the -CF3 side group effectively decreases the trap density of the perovskite film by forming interactions with the undercoordinated Pb2+ ions and significantly inhibits the nonradiative recombination in the derived PSC, leading to an enhanced open-circuit voltage (Voc) from 0.96 to 1.10 V after passivation. Also, the CFPA post-treatment enables better energy-level alignment between the conduction band minimum of CsPbI2Br perovskite and [6,6]-phenyl C61 butyric acid methyl ester, thereby enhancing the charge extraction from the perovskite to the charge transport layer. These combined benefits result in a significant enhancement of the power conversion efficiency from 11.22 to 14.37% for inverted CsPbI2Br PSCs. The device without encapsulation exhibits a degradation of only ≈4% after 1992 h in a N2 glovebox.

9.
Inorg Chem ; 2024 Feb 12.
Artículo en Inglés | MEDLINE | ID: mdl-38346933

RESUMEN

Zintl compounds have continuously received significant attention, primarily due to their structural characteristics that align with the properties of the electron crystal and phonon glass. In this study, the crystal structure and thermoelectric properties of the quaternary Zintl chalcogenide BaScCuTe3 are investigated. The band structure calculations for BaScCuTe3 reveal a slight energy split of 0.08 eV between the second valence band and the valence band maximum, suggesting the presence of multiband-transport behaviors. Substitution of rare earth Gd for Sc is conducted, which significantly increases the hole concentration from 4.1 × 1019 cm-3 to 8.2 × 1019 cm-3 at room temperature. Meanwhile, the Seebeck coefficient increases because of the participation of the second valence band. A maximum power factor of 6.56 µW/cm·K2 at 773 K is obtained, which is 72% higher than that of the pristine sample. Moreover, the lattice thermal conductivity decreases from 0.57 W/m·K for BaScCuTe3 to 0.48 W/m·K for BaSc0.97Gd0.03CuTe3 at 773 K, owing to the introduction of point-defect scattering. As a result, there is a noteworthy improvement in the thermoelectric figure of merit zT, increasing from 0.44 for the undoped sample to 0.85 for BaSc0.98Gd0.02CuTe3. Considering these findings, BaScCuTe3 exhibits great potential and holds promise for further investigation in the field of thermoelectric materials.

10.
Phys Chem Chem Phys ; 26(5): 4702-4715, 2024 Jan 31.
Artículo en Inglés | MEDLINE | ID: mdl-38251937

RESUMEN

To identify superalkali-alkaline earthide ion pairs, it's theoretically shown that, as a novel class of excess electron superalkali compounds, both chair and boat forms of (AM-HMHC)-AM' (AM = Li, Na, and K; AM' = Be, Mg, and Ca; HMHC = 1,4,7,10,13,16-hexamethyl-1,4,7,10,13,16-hexaazacyclooctadecane) are good candidates. An attractive superalkali-alkaline earthide ion pair in δ+(AM-HMHC)-AM'δ- is firstly exhibited, which possesses alkaline-earthide characteristics and nonlinear optical response superior to similar M+(calix[4]pyrrole)M'- (M = Li, Na, and K; M' = Be, Mg, and Ca) with high stability. The electronic and vibrational second order hyperpolarizabilities and the frequency-dependent first hyperpolarizabilities of δ+(AM-HMHC)-AM'δ- are presented. For each pair of (AM-HMHC)-AM', the boat conformation is preferred to its chair one in the case of Hyper-Rayleigh scattering response (ßHRS). These alkaline earthides suggest prominently high ßHRS up to 2.59 × 104 a.u. (boat forms of δ+(Na-HMHC)-Caδ-). We expect that this work will inspire the preparation and characterization of these new alkaline earthides as high-performance NLO materials.

11.
J Chem Phys ; 160(9)2024 Mar 07.
Artículo en Inglés | MEDLINE | ID: mdl-38426522

RESUMEN

All-inorganic CsPbI2Br inverted perovskite solar cells (PSCs) have drawn increasing attention because of their outstanding thermal stability and compatible process with tandem cells. However, relatively low open circuit voltage (Voc) has lagged their progress far behind theoretical limits. Herein, we introduce phenylmethylammonium iodide and 4-trifluoromethyl phenylmethylammonium iodide (CFPMAI) on the surface of a CsPbI2Br perovskite film and investigate their passivation effects. It is found that CFPMAI with a -CF3 substituent significantly decreases the trap density of the perovskite film by forming interactions with the under-coordinated Pb2+ ions and effectively suppresses the non-radiative recombination in the resulting PSC. In addition, CFPMAI surface passivation facilitates the optimization of energy-level alignment at the CsPbI2Br perovskite/[6,6]-phenyl C61 butyric acid methyl ester interface, resulting in improved charge extraction from the perovskite to the charge transport layer. Consequently, the optimized inverted CsPbI2Br device exhibits a markedly improved champion efficiency of 14.43% with a Voc of 1.12 V, a Jsc of 16.31 mA/cm2, and a fill factor of 79.02%, compared to the 10.92% (Voc of 0.95 V) efficiency of the control device. This study confirms the importance of substituent groups on surface passivation molecules for effective passivation of defects and optimization of energy levels, particularly for Voc improvement.

12.
Sleep Breath ; 28(3): 1319-1327, 2024 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-38413555

RESUMEN

PURPOSE: Diaphragmatic impairment has been reported in obstructive sleep apnea-hypopnea syndrome (OSAHS) patients. However, the risk factors of diaphragmatic dysfunction are unclear. This study was conducted to evaluate the diaphragmatic function and to investigate impact factors of ultrasonographic changes of the diaphragm in OSAHS patients. METHODS: This cross-sectional study recruited 150 snoring patients. All patients were divided into the control group (AHI < 5/h, n = 20), the mild-to-moderate OSAHS group (5/h ≤ AHI ≤ 30/h, n = 61), and the severe OSAHS group (AHI > 30/h, n = 69). Diaphragmatic thickness at function residual capacity (TFRC) and total lung capacity (TTLC) were measured by two-dimensional ultrasound, and the diaphragmatic excursion during tidal and deep breath was measured by M-mode ultrasound. The diaphragmatic thickening fraction (TF) was calculated. Spearman analysis and multiple linear stepwise regression analysis were conducted to analyze the impact factors of diaphragmatic function. RESULTS: TFRC in the control group, mild-to-moderate OSAHS group, and severe OSAHS group was 1.23 (1.10, 1.39) mm, 1.60 (1.43, 1.85) mm, and 1.90 (1.70, 2.25) mm; TTLC was 2.75 (2.53, 2.93) mm, 3.25 (2.90, 3.55) mm, and 3.60 (3.33, 3.90) mm, and TF was 119.23% (102.94, 155.97), 96.55% (74.34, 119.11), and 85.29% (60.68,101.22). There were across-group significant differences in TFRC, TTLC, and TF (P < 0.05). The oxygen desaturation index was the influencing factor of TFRC, TTLC, and TF (P < 0.05). CONCLUSION: The diaphragm is thickened and diaphragmatic contractility is decreased in OSAHS patients. Nocturnal intermittent hypoxia is a risk factor for diaphragmatic hypertrophy and impaired diaphragmatic contractility.


Asunto(s)
Diafragma , Apnea Obstructiva del Sueño , Ultrasonografía , Humanos , Apnea Obstructiva del Sueño/fisiopatología , Apnea Obstructiva del Sueño/diagnóstico por imagen , Diafragma/fisiopatología , Diafragma/diagnóstico por imagen , Masculino , Estudios Transversales , Femenino , Persona de Mediana Edad , Adulto , Polisomnografía
13.
Proc Natl Acad Sci U S A ; 118(1)2021 01 05.
Artículo en Inglés | MEDLINE | ID: mdl-33443222

RESUMEN

Effective therapies for alcohol-associated liver disease (ALD) are limited; therefore, the discovery of new therapeutic agents is greatly warranted. Toll-like receptor 7 (TLR7) is a pattern recognition receptor for single-stranded RNA, and its activation prevents liver fibrosis. We examined liver and intestinal damage in Tlr7-/- mice to determine the role of TLR7 in ALD pathogenesis. In an alcoholic hepatitis (AH) mouse model, hepatic steatosis, injury, and inflammation were induced by chronic binge ethanol feeding in mice, and Tlr7 deficiency exacerbated these effects. Because these results demonstrated that endogenous TLR7 signaling activation is protective in the AH mouse model, we hypothesized that TLR7 activation may be an effective therapeutic strategy for ALD. Therefore, we investigated the therapeutic effect of TLR7 agonistic agent, 1Z1, in the AH mouse model. Oral administration of 1Z1 was well tolerated and prevented intestinal barrier disruption and bacterial translocation, which thus suppressed ethanol-induced hepatic injury, steatosis, and inflammation. Furthermore, 1Z1 treatment up-regulated the expression of antimicrobial peptides, Reg3b and Reg3g, in the intestinal epithelium, which modulated the microbiome by decreasing and increasing the amount of Bacteroides and Lactobacillus, respectively. Additionally, 1Z1 up-regulated intestinal interleukin (IL)-22 expression. IL-22 deficiency abolished the protective effects of 1Z1 in ethanol-induced liver and intestinal damage, suggesting intestinal IL-22 as a crucial mediator for 1Z1-mediated protection in the AH mouse model. Collectively, our results indicate that TLR7 signaling exerts protective effects in the AH mouse model and that a TLR7 ligand, 1Z1, holds therapeutic potential for the treatment of AH.


Asunto(s)
Etanol/toxicidad , Interleucinas/metabolismo , Mucosa Intestinal/metabolismo , Hepatopatías Alcohólicas/tratamiento farmacológico , Glicoproteínas de Membrana/metabolismo , Transducción de Señal/efectos de los fármacos , Receptor Toll-Like 7/metabolismo , Administración Oral , Animales , Bacteroides/efectos de los fármacos , Modelos Animales de Enfermedad , Hígado Graso/complicaciones , Hígado Graso/genética , Hígado Graso/metabolismo , Femenino , Microbioma Gastrointestinal/efectos de los fármacos , Inflamación/complicaciones , Inflamación/genética , Inflamación/metabolismo , Mucosa Intestinal/efectos de los fármacos , Lactobacillus/efectos de los fármacos , Ligandos , Hepatopatías Alcohólicas/genética , Hepatopatías Alcohólicas/metabolismo , Hepatopatías Alcohólicas/fisiopatología , Glicoproteínas de Membrana/agonistas , Glicoproteínas de Membrana/genética , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , MicroARNs , Proteínas Asociadas a Pancreatitis/genética , Proteínas Asociadas a Pancreatitis/metabolismo , Polietilenglicoles/química , Polietilenglicoles/farmacología , Proteínas Citotóxicas Formadoras de Poros/genética , Proteínas Citotóxicas Formadoras de Poros/metabolismo , Transducción de Señal/genética , Uniones Estrechas/efectos de los fármacos , Uniones Estrechas/patología , Receptor Toll-Like 7/agonistas , Receptor Toll-Like 7/genética , Interleucina-22
14.
Artículo en Inglés | MEDLINE | ID: mdl-38914814

RESUMEN

PURPOSE: This study aims to examine the relationship between excessive daytime sleepiness (EDS) and attention impairment in Chinese individuals with obstructive sleep apnea (OSA). METHODS: A total of 1996 OSA patients with an apnea-hypopnea index (AHI) of ≥ 5 events per hour were included in this study. EDS was measured using the Epworth Sleepiness Scale (ESS), while cognitive function was assessed using the Mini-Mental State Examination (MMSE) and the Montreal Cognitive Assessment (MoCA). RESULTS: OSA patients with EDS demonstrated higher body mass index (BMI), comorbidities of hypertension and diabetes, decreased N3 sleep, increased AHI and ODI, as well as lower minimum oxygen saturation. Despite no significant differences in total cognitive scores assessed by MMSE and MoCA, individuals with comorbid sleepiness exhibited more evident attention deficits in the subdomains of MoCA. Stratified analysis indicated that regardless of age, educational level was the primary factor influencing attention in the AHI < =20 group. In the AHI > 20 group, attention impairment in patients younger than 40 remained significantly associated with education level, whereas for individuals aged 40 and above, attention deficits were associated with education level, age, and daytime sleepiness. The interaction analysis indicated that OSA severity modulated the impact of sleepiness on attention in patients aged 40 and above. CONCLUSION: A significant correlation was observed between EDS and attention deficits in Chinese individuals diagnosed with OSA, with a particular emphasis on patients aged 40 and above. The severity of OSA modulates the impact of sleepiness on attention in patients aged 40 and above.

15.
J Craniofac Surg ; 35(4): 1261-1263, 2024 Jun 01.
Artículo en Inglés | MEDLINE | ID: mdl-38349356

RESUMEN

OBJECTIVE: Depressed scarring is a common complication after incisional upper blepharoplasty and frequently contributes to patient dissatisfaction. Correcting this deformity presents a significant challenge for oculoplastic surgeons. This study aims to investigate the clinical effectiveness of employing the turnover orbicularis-septum composite flap technique in correcting depressed scars after double eyelid surgery. METHODS: This is a retrospective study of 118 patients who underwent revision blepharoplasty with depressed scar from November 2020 to February 2023. During the revision procedure, the adhesions of the original scar were meticulously dissected, and the residual orbital fat was thoroughly released. The orbicularis-septum composite flap was then inverted downward and smoothly laid over the depressed scar area to address the tissue deficit. After surgery, patient satisfaction was evaluated by assessing the improvement of the depressed scars and the shape of the double eyelid folds. RESULTS: Follow-up assessments were conducted over a period of 6 to 24 months postoperatively. The results were judged as fully satisfied in 78 cases (66.1%), basically satisfied in 32 cases (27.1%), and unsatisfied in 8 cases (6.8%). Among the unsatisfied patients, 5 patients complained of eyelid fold shallow or disappear, and 3 patients complained of asymmetry. All patients exhibited varying degrees of improvement in the depressed scars. CONCLUSIONS: The turnover orbicularis-septum composite flap technique provides an effective approach for the treatment of depressed scars with a high satisfaction rate.


Asunto(s)
Blefaroplastia , Cicatriz , Satisfacción del Paciente , Colgajos Quirúrgicos , Humanos , Blefaroplastia/métodos , Femenino , Cicatriz/cirugía , Cicatriz/etiología , Estudios Retrospectivos , Masculino , Adulto , Persona de Mediana Edad , Reoperación , Complicaciones Posoperatorias/cirugía , Párpados/cirugía , Anciano , Resultado del Tratamiento
16.
Sensors (Basel) ; 24(7)2024 Mar 29.
Artículo en Inglés | MEDLINE | ID: mdl-38610420

RESUMEN

This work proposes a highly sensitive sandwich heterostructure multimode optical fiber microbend sensor for heart rate (HR), respiratory rate (RR), and ballistocardiography (BCG) monitoring, which is fabricated by combining a sandwich heterostructure multimode fiber Mach-Zehnder interferometer (SHMF-MZI) with a microbend deformer. The parameters of the SHMF-MZI sensor and the microbend deformer were analyzed and optimized in detail, and then the new encapsulated method of the wearable device was put forward. The proposed wearable sensor could greatly enhance the response to the HR signal. The performances for HR, RR, and BCG monitoring were as good as those of the medically approved commercial monitors. The sensor has the advantages of high sensitivity, easy fabrication, and good stability, providing the potential for application in the field of daily supervision and health monitoring.

17.
Angew Chem Int Ed Engl ; : e202406612, 2024 Jun 25.
Artículo en Inglés | MEDLINE | ID: mdl-38924325

RESUMEN

Piperidines are widely present in small molecule drugs and natural products. Despite many methods have been developed for their synthesis, new approaches to polysubstituted piperidines are highly desirable. This work presents a radical (4+2) cycloaddition reaction for synthesis of piperidines featuring dense substituents at 3,4,5-positions that are not readily accessible by known methods. Using commercially available diboron(4) compounds and 4-phenylpyridine as the catalyst precursors, the boronyl radical-catalyzed cycloaddition between 3-aroyl azetidines and various alkenes, including previously unreactive 1,2-di-, tri-, and tetrasubstituted alkenes, has delivered the polysubstituted piperidines in generally high yield and diastereoselectivity. The reaction also features high modularity, atom economy, broad substrate scope, metal-free conditions, simple catalysts and operation. The utilization of the products has been demonstrated by selective transformations. A plausible mechanism, with the ring-opening of azetidine as the rate-limiting step, has been proposed based on the experimental and computational results.

18.
Angew Chem Int Ed Engl ; : e202406650, 2024 May 31.
Artículo en Inglés | MEDLINE | ID: mdl-38818631

RESUMEN

Dispersion of single atoms (SAs) in the host is important for optimizing catalytic activity. Herein, we propose a novel strategy to tune oxygen vacancies in CeO2-X directionally anchoring the single atom platinum (PtSA), which is uniformly dispersed on the rGO. The catalyst's performance for the hydrogen evolution reaction (HER) can be enhanced by controlling different densities of CeO2-X in rGO. The PtSA performs best optimally densified and loaded on homogeneous and moderately densified CeO2-X/rGO (PtSA-M-CeO2-X/rGO). It exhibited high activity in HER with an overpotential of 25 mV at 0.5 M H2SO4 and 33 mV at 1 KOH than that of almost reported electrocatalysts. Furthermore, it exhibited stability for 90 hours at -100 mA cm-2 in 1 KOH and -150 mA cm-2 in 0.5 M H2SO4 conditions, respectively. Through comprehensive experiments and theoretical calculations, the suitable dispersion density of PtSA on the defects of CeO2-X with more active sites gives the potential for practical applications. This research paves the way for developing single-atom catalysts with exceptional catalytic activity and stability, holding promise in advanced green energy conversion through defects engineering.

19.
J Am Chem Soc ; 2023 Feb 10.
Artículo en Inglés | MEDLINE | ID: mdl-36763965

RESUMEN

In contrast to the traditional and widely-used cycloaddition reactions involving at least a π bond component, a [2σ + 2σ] radical cycloaddition between bicyclo[1.1.0]butanes (BCBs) and cyclopropyl ketones has been developed to provide a modular, concise, and atom-economical synthetic route to substituted bicyclo[3.1.1]heptane (BCH) derivatives that are 3D bioisosteres of benzenes and core skeleton of a number of terpene natural products. The reaction was catalyzed by a combination of simple tetraalkoxydiboron(4) compound B2pin2 and 3-pentyl isonicotinate. The broad substrate scope has been demonstrated by synthesizing a series of new highly functionalized BCHs with up to six substituents on the core with up to 99% isolated yield. Computational mechanistic investigations supported a pyridine-assisted boronyl radical catalytic cycle.

20.
Nat Prod Rep ; 40(9): 1498-1520, 2023 09 20.
Artículo en Inglés | MEDLINE | ID: mdl-37581222

RESUMEN

Time span of literature covered: up to mid-2023Iterative type I polyketide synthases (iPKSs) are outstanding natural chemists: megaenzymes that repeatedly utilize their catalytic domains to synthesize complex natural products with diverse bioactivities. Perhaps the most fascinating but least understood question about type I iPKSs is how they perform the iterative yet programmed reactions in which the usage of domain combinations varies during the synthetic cycle. The programmed patterns are fulfilled by multiple factors, and strongly influence the complexity of the resulting natural products. This article reviews selected reports on the structural enzymology of iPKSs, focusing on the individual domain structures followed by highlighting the representative programming activities that each domain may contribute.


Asunto(s)
Productos Biológicos , Sintasas Poliquetidas , Sintasas Poliquetidas/metabolismo , Dominio Catalítico , Catálisis , Productos Biológicos/química
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