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1.
Angew Chem Int Ed Engl ; : e202203955, 2022 Apr 19.
Artigo em Inglês | MEDLINE | ID: mdl-35441462

RESUMO

In natural photosynthesis, the architecture of multiproteins integrates more chromophores than redox centers and simultaneously creates a well-controlled environment around the active site. Herein, we demonstrate that these features can be emulated in a prototype hydrogen-bonded organic framework (HOF) through simply varying the proportion of metalated porphyrin in the structure. Further studies demonstrate that changing the metalloporphyrin content not only realizes a fine tuning of the photosensitizer/catalyst ratio, but also alters the microenvironment surrounding the active site and the charge separation efficiency. As a result, the obtained material achieves the challenging overall CO2 reduction with a high HCOOH production rate (29.8 µmol g-1 h-1 , scavenger free), standing out from existing competitors. This work unveils that the degree of metalation is vital to the catalytic activity of the porphryinic framework, presenting as a new strategy to optimize the performance of heterogeneous catalysts.

2.
ACS Appl Mater Interfaces ; 14(18): 21050-21058, 2022 May 11.
Artigo em Inglês | MEDLINE | ID: mdl-35476406

RESUMO

Photocatalytic CO2 reduction is one of the most cost-effective and environmentally friendly techniques of converting CO2 into high-value compounds and/or fuels. However, the performance of most current photocatalytic CO2 reduction catalysts is less than satisfactory for practical applications. Here, we synthesized a heterogeneous structure by integrating Cu2O and a porphyrin hydrogen-bonded organic framework (PFC-45), which was then fabricated into a thin-film catalyst on carbolic paper (CP) using a facile electrophoretic deposition technology. With improved electron-hole separation efficiency and visible-light-harvesting ability, this film (PFC-45/Cu2O@CP) significantly enhanced CO2-to-CO photoreduction, exceeding 2.4 and 3.2 times that of PFC-45@CP and PFC-45/Cu2O particles, respectively. Remarkably, PFC-45/Cu2O@CP also exhibited high selectivity (99%) and outstanding activity (11.81 µmol g-1 h-1) for photocatalytic CO2 reduction in pure water without any sacrificial agent. This work demonstrates a new strategy to design photocatalysts for efficient CO2 reduction.

3.
Angew Chem Int Ed Engl ; 61(6): e202115854, 2022 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-34877789

RESUMO

Under topological guidance, the self-assembly process based on a tetratopic porphyrin synthon results in a hydrogen-bonded organic framework (HOF) with the predicted square layers topology (sql) but unsatisfied stability. Strikingly, simply introducing a transition metal in the porphyrin center does not change the network topology but drastically causes noticeable change on noncovalent interaction, orbital overlap, and molecular geometry, therefore ultimately giving rise to a series of metalloporphyrinic HOFs with high surface area, and excellent stability (intact after being soaked in boiling water, concentrated HCl, and heated to 270 °C). On integrating both photosensitizers and catalytic sites into robust backbones, this series of HOFs can effectively catalyze the photoreduction of CO2 to CO, and their catalytic performances greatly depend on the chelated metal species in the porphyrin centers. This work enriches the library of stable functional HOFs and expands their applications in photocatalytic CO2 reduction.

4.
Research (Wash D C) ; 2021: 9874273, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34778792

RESUMO

The poor electrical conductivity of metal-organic frameworks (MOFs) has been a stumbling block for its applications in many important fields. Therefore, exploring a simple and effective strategy to regulate the conductivity of MOFs is highly desired. Herein, anionic guest molecules are incorporated inside the pores of a cationic MOF (PFC-8), which increases its conductivity by five orders of magnitude while maintaining the original porosity. In contrast, the same operation in an isoreticular neutral framework (PFC-9) does not bring such a significant change. Theoretical studies reveal that the guest molecules, stabilized inside pores through electrostatic interaction, play the role of electron donors as do in semiconductors, bringing in an analogous n-type semiconductor mechanism for electron conduction. Therefore, we demonstrate that harnessing electrostatic interaction provides a new way to regulate the conductivity of MOFs without necessarily altering the original porous structure. This strategy would greatly broaden MOFs' application potential in electronic and optoelectronic technologies.

5.
Chemistry ; 27(42): 10957-10965, 2021 Jul 26.
Artigo em Inglês | MEDLINE | ID: mdl-33884685

RESUMO

Porous materials have been investigated as efficient photochromic platforms for detecting hazardous radiation, while the utilization of hydrogen bonded organic frameworks (HOFs) in this field has remained intact. Herein, two HOFs were synthesized through self-assembly of tetratopic viologen ligand and formic acid (PFC-25, PFC-26), as a new class of "all-organic" radiochromic smart material, opening a gate for HOFs in this field. PFC-26 is active upon both X-ray and UV irradiation, while PFC-25 is only active upon X-ray irradiation. The same building block yet different radiochromic behaviors of PFC-25 and PFC-26 allow us to gain a deep mechanistic understanding of the factors that control the detection specificity. Theoretical and experimental studies reveal that the degree of π-conjugation of viologen ligand is highly related to the threshold energy of triggering a charge transfer, therefore being a vital factor for the particularity of radiochromic materials. Thanks to its convenient processibility, nanoparticle size, and UV silence, PFC-25 can be further fabricated into a portable naked-eye sensor for X-ray detection, which shows obvious color change with the merits of high transmittance contrast, good sensitivity (reproducible dose threshold of 3.5 Gy), and excellent stability. The work exhibits the promising practical potentials of HOF materials in photochromic technology.


Assuntos
Hidrogênio , Viologênios , Ligação de Hidrogênio , Raios X
6.
Chem Commun (Camb) ; 56(11): 1737-1740, 2020 Feb 06.
Artigo em Inglês | MEDLINE | ID: mdl-31938796

RESUMO

The Pd(0)-catalyzed tandem intermolecular syn-carbopalladation/asymmetric C-H alkenylation reaction of N-ferrocenyl propiolamides with aryl iodides has been realized, generating planar chiral ferrocene[1,2-d] pyrrolinones in good yields. Through employing BINOL-derived phosphoramidite ligands, up to 95% ee is achieved.

7.
Angew Chem Int Ed Engl ; 59(11): 4385-4390, 2020 Mar 09.
Artigo em Inglês | MEDLINE | ID: mdl-31943675

RESUMO

Although many ionic metal-organic frameworks (MOFs) have been reported, little is known about how the charge of the skeleton affects the properties of the MOF materials. Herein we report how the chemical stability of MOFs can be substantially improved through embedding electrostatic interactions in structure. A MOF with a cationic skeleton is impervious to extremely acidic, oxidative, reductive, and high ionic strength conditions, such as 12 m HCl (301 days), aqua regia (86 days), H2 O2 (30 days), and seawater (30 days), which is unprecedented for MOFs. DFT calculations suggested that steric hinderance and the repulsive interaction of the cationic framework toward positively charged species in microenvironments protects the vulnerable bonds in the structure. Diverse functionalities can be bestowed by substituting the counterions of the charged framework with identically charged functional species, which broadens the horizon in the design of MOFs adaptable to a demanding environment with specific functionalities.

8.
J Org Chem ; 84(24): 16068-16075, 2019 12 20.
Artigo em Inglês | MEDLINE | ID: mdl-31769673

RESUMO

A novel tetrabutylammonium iodide (TBAI)-promoted three-component reaction of carboxylic acid with alkene and alcohol has been developed, which represents facile and straightforward access to polysubstituted γ-lactone skeletons in moderate-to-good yields. This methodology is distinguished by the use of a commercial catalyst and readily available starting materials, wide substrate scope, and operational simplicity. Mechanistic studies suggested that this transformation went through a radical process.

9.
World J Pediatr ; 15(6): 572-579, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31342464

RESUMO

BACKGROUND: Although localized neuroblastoma has a good prognosis, some cases have undergone treatment failure or recurrence. Apart from biologic features such as MYCN status, we wondered whether some characteristics of growing tumors are prognostic, such as a well-encapsulated mass without infiltration of vital organs. We analyzed the diagnostic utility of image-defined risk factors (IDRFs) to predict successful treatment and prognosis. The overall goal was to achieve maximum cure rates for patients with localized neuroblastoma through a better understanding of clinical characteristics. METHODS: We retrospectively reviewed the images of patients with localized neuroblastoma who were enrolled between June 1998 and December 2012 at a single institution in Shanghai, China. Unequivocal categorization regarding IDRFs was available in 67 patients. IDRF was assessed at diagnosis and after four cycles of neoadjuvant chemotherapy, on average. The median follow-up period was 84 months (range: 48-132 months) after diagnosis. RESULTS: MRI and CT indicated a total of 177 IDRFs in these 67 patients. Logistic regression analysis revealed a highly significant negative correlation between the numbers of IDRFs and the possibility of complete removal of neuroblastoma. Intraspinal extension of the tumor, compression of the trachea, and encasement of the main artery in localized neuroblastoma were predictors for incomplete tumor resection. According to univariate analysis, ≥ 4 IDRFs and intraspinal extension of the tumor were significant indicators of poor prognosis. CONCLUSIONS: The number of IDRFs was useful in predicting surgical outcome and event-free survival. The number of IDRFs should be considered in protocol planning, instead of IDRF presence or absence.


Assuntos
Neuroblastoma/diagnóstico por imagem , Neuroblastoma/patologia , Adolescente , Criança , Pré-Escolar , Feminino , Humanos , Lactente , Imageamento por Ressonância Magnética , Masculino , Neuroblastoma/mortalidade , Neuroblastoma/terapia , Prognóstico , Estudos Retrospectivos , Medição de Risco/métodos , Fatores de Risco , Tomografia Computadorizada por Raios X , Resultado do Tratamento
10.
IUBMB Life ; 69(9): 700-705, 2017 09.
Artigo em Inglês | MEDLINE | ID: mdl-28834160

RESUMO

Elevated homocysteine levels are known to be a risk factor for congenital cardiac septal defects (CCSDs), but the mechanism underlying this effect is unknown. The genetic variants that were significantly associated with circulating homocysteine concentrations have been systematically identified through the genome-wide association studies of one-carbon core metabolites. To examine the role of the genome-wide significant homocysteine related variants in the occurrence of CCSDs, we investigated the association between these variants and CCSDs in Han Chinese populations. Five variants of the genome-wide significant homocysteine-related genes were selected for analysis in two stages of case-controlled studies with a total of 904 CCSD patients and 997 controls. SYT9 expression was detected in human cardiovascular tissue using qRT-PCR. The intronic variant rs11041321 of the SYT9 gene was associated with an increased risk of developing CCSDs in both the separate and combined case-controlled studies. Combined samples from the two stage cohorts had a significant elevation in CCSD risk for the T allele (OR = 1.43, P = 2.6 × 10-6 ), CT genotype and TT genotype (CT: OR = 1.30, TT: OR = 2.21; P = 1 × 10-4 ) compared with the wild-type C allele and CC genotype, respectively. The risky T allele carriers exhibited decreased SYT9 mRNA expression, compared with wild-type C allele carriers. The intronic SYT9 variant rs11041321, which exhibits a significant genome-wide association with circulating homocysteine, was associated with the occurrence of CCSDs. This finding helps to characterize the unexpected role of SYT9 in homocysteine metabolism and the development of CCSDs, which further highlighted the interplay of diet, genetics, and human birth defects. © 2017 IUBMB Life, 69(9):700-705, 2017.


Assuntos
Predisposição Genética para Doença , Defeitos dos Septos Cardíacos/genética , Homocisteína/genética , Sinaptotagminas/genética , Alelos , Feminino , Expressão Gênica/genética , Estudos de Associação Genética , Genótipo , Defeitos dos Septos Cardíacos/patologia , Homocisteína/metabolismo , Humanos , Masculino , Polimorfismo de Nucleotídeo Único/genética , Fatores de Risco
11.
Chin Med J (Engl) ; 129(22): 2733-2740, 2016 11 20.
Artigo em Inglês | MEDLINE | ID: mdl-27824007

RESUMO

BACKGROUND: Tetrahydrobiopterin (BH4) is an essential cofactor of nitric oxide synthases (NOSs) for the synthesis of nitric oxide (NO). BH4 therapy can reverse the disease-related redox disequilibrium observed with BH4 deficiency. However, whether BH4 exerts a protective effect against radiation-induced damage to cardiomyocytes remains unknown. METHODS: Clonogenic assays were performed to determine the effects of X-ray on H9c2 cells with or without BH4 treatment. The contents of lactate dehydrogenase (LDH), superoxide dismutase (SOD), and malondialdehyde (MDA) in H9c2 cells were measured to investigate oxidative stress levels. The cell cycle undergoing radiation with or without BH4 treatment was detected using flow cytometry. The expression levels of proteins in the phosphatidylinositol 3 kinase (PI3K)/protein kinase B (AKT)/P53 signaling pathway, inducible NOS (iNOS), and endothelial NOS (eNOS) were examined using Western blotting. RESULTS: X-ray radiation significantly inhibited the growth of H9c2 cells in a dose-dependent manner, whereas BH4 treatment significantly reduced the X-ray radiation-induced growth inhibition (control group vs. X-ray groups, respectively, P< 0.01). X-ray radiation induced LDH release, apoptosis, and G0/G1 peak accumulation, significantly increasing the level of MDA and the production of NO, and decreased the level of SOD (control group vs. X-ray groups, respectively, P < 0.05 or P < 0.01). By contrast, BH4 treatment can significantly reverse these processes (BH4 treatment groups vs. X-ray groups, P < 0.05 or P < 0.01). BH4 reversed the X-ray radiation-induced expression alterations of apoptosis-related molecules, including B-cell lymphoma-2 (Bcl-2), Bcl-2 associated X protein, and caspase-3, and molecules of the PI3K/Akt/P53 signaling pathway. BH4 enhanced the production of NO in 2 Gy and 4 Gy radiated groups by upregulating eNOS protein expression and downregulating iNOS protein expression. CONCLUSIONS: BH4 treatment can protect against X-ray-induced cardiomyocyte injury, possibly by recoupling eNOS rather than iNOS. BH4 treatment also decreased oxidative stress in radiated H9c2 cells.


Assuntos
Biopterina/análogos & derivados , Miócitos Cardíacos/efeitos dos fármacos , Miócitos Cardíacos/efeitos da radiação , Animais , Antioxidantes/metabolismo , Apoptose/efeitos dos fármacos , Biopterina/farmacologia , Ciclo Celular/efeitos dos fármacos , Linhagem Celular , Ensaio de Imunoadsorção Enzimática , L-Lactato Desidrogenase/metabolismo , Miócitos Cardíacos/citologia , Ratos , Transdução de Sinais
12.
Org Lett ; 17(9): 2046-9, 2015 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-25860406

RESUMO

The palladium-catalyzed enantioselective intramolecular C-H arylation of N-(2-haloaryl)-P,P-diphenylphosphinic amides furnishes P-stereogenic phosphine oxide derivatives in 61-99% yield with 88-97% ee. The catalyst generated in situ from a TADDOL-derived phosphoramide ligand and Pd(dba)2 is optimum in terms of yield and enantioselectivities.

13.
Org Lett ; 16(20): 5336-8, 2014 Oct 17.
Artigo em Inglês | MEDLINE | ID: mdl-25264929

RESUMO

The palladium-catalyzed intramolecular C-H arylation reaction of N-(2-bromoaryl)ferrocenecarboxamides furnishes planar chiral ferrocene derivatives. TADDOL-derived phosphoramide ligands induce enantioselectivities ranging from 91:9 to 98:2 er.

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