Most organic polymeric materials have high flammability, for which the large amounts of smoke, toxic gases, heat, and melt drips produced during their burning cause immeasurable damages to human life ...and property every year. Despite some desirable results having been achieved by conventional flame‐retardant methods, their application is encountering more and more difficulties with the ever‐increasing high flame‐retardant requirements such as high flame‐retardant efficiency, great persistence, low release of heat, smoke, and toxic gases, and more importantly not deteriorating or even enhancing the overall properties of polymers. Under such condition, some advanced flame‐retardant methods have been developed in the past years based on “all‐in‐one” intumescence, nanotechnology, in situ reinforcement, intrinsic char formation, plasma treatment, biomimetic coatings, etc., which have provided potential solutions to the dilemma of conventional flame‐retardant methods. This review briefly outlines the development, application, and problems of conventional flame‐retardant methods, including bulk‐additive, bulk‐copolymerization, and surface treatment, and focuses on the raise, development, and potential application of advanced flame‐retardant methods. The future development of flame‐retardant methods is further discussed.
Flame‐retardant methods for polymeric materials are reviewed with particular focus on advanced flame‐retardant methods developed in recent years. Both the advantages and drawbacks of these methods are discussed, and prospects for the future development of flame‐retardant methods are presented. It is hoped that this review will guide the development of flame‐retardant polymeric materials.
Summary
Quercus dentata Thunb., a dominant forest tree species in northern China, has significant ecological and ornamental value due to its adaptability and beautiful autumn coloration, with color ...changes from green to yellow into red resulting from the autumnal shifts in leaf pigmentation. However, the key genes and molecular regulatory mechanisms for leaf color transition remain to be investigated.
First, we presented a high‐quality chromosome‐scale assembly for Q. dentata. This 893.54 Mb sized genome (contig N50 = 4.21 Mb, scaffold N50 = 75.55 Mb; 2n = 24) harbors 31 584 protein‐coding genes. Second, our metabolome analyses uncovered pelargonidin‐3‐O‐glucoside, cyanidin‐3‐O‐arabinoside, and cyanidin‐3‐O‐glucoside as the main pigments involved in leaf color transition. Third, gene co‐expression further identified the MYB‐bHLH‐WD40 (MBW) transcription activation complex as central to anthocyanin biosynthesis regulation.
Notably, transcription factor (TF) QdNAC (QD08G038820) was highly co‐expressed with this MBW complex and may regulate anthocyanin accumulation and chlorophyll degradation during leaf senescence through direct interaction with another TF, QdMYB (QD01G020890), as revealed by our further protein–protein and DNA–protein interaction assays.
Our high‐quality genome assembly, metabolome, and transcriptome resources further enrich Quercus genomics and will facilitate upcoming exploration of ornamental values and environmental adaptability in this important genus.
2-(2-Phenylethyl)chromones (PECs) are the principal constituents contributing to the distinctive fragrance of agarwood. How PECs are biosynthesized is currently unknown. In this work, we describe a ...diarylpentanoid-producing polyketide synthase (PECPS) identified from Aquilaria sinensis. Through biotransformation experiments using fluorine-labeled substrate, transient expression of PECPS in Nicotiana benthamiana, and knockdown of PECPS expression in A. sinensis calli, we demonstrate that the C
-C
-C
scaffold of diarylpentanoid is the common precursor of PECs, and PECPS plays a crucial role in PECs biosynthesis. Crystal structure (1.98 Å) analyses and site-directed mutagenesis reveal that, due to its small active site cavity (247 Å
), PECPS employs a one-pot formation mechanism including a "diketide-CoA intermediate-released" step for the formation of the C
-C
-C
scaffold. The identification of PECPS, the pivotal enzyme of PECs biosynthesis, provides insight into not only the feasibility of overproduction of pharmaceutically important PECs using metabolic engineering approaches, but also further exploration of how agarwood is formed.
The development of enantioselective alkyl–alkyl cross‐couplings with coinstantaneous formation of a stereogenic center without the use of sensitive organometallic species is attractive yet ...challenging. Herein, we report the intermolecular regio‐ and enantioselective formal hydrofunctionalizations of acrylamides, forging a stereogenic center α‐position to the newly formed Csp3–Csp3 bond for the first time. The use of a newly developed chiral ligand enables the electronically‐reversed formal hydrofunctionalizations, including hydroalkylation, hydrobenzylation, and hydropropargylation, offering an efficient way to access diverse enantioenriched amides with a tertiary α‐stereogenic carbon center which is facile to racemize. This operationally simple protocol allows for the anti‐Markovnikov enantioselective hydroalkylation, and unprecedented hydrobenzylation, hydropropargylation under mild conditions with excellent functional group compatibility, delivering a wide range of amides with excellent levels of enantioselectivity.
Alkyl–alkyl bond‐forming with coinstantaneous formation of a stereogenic center is attractive yet challenging. Herein, the intermolecular, regio‐ and enantioselective formal hydrofunctionalization of alkenes to forge a stereogenic center in the α‐position to the newly formed alkyl–alkyl bond is reported for the first time, providing a facile access to a wide range of α‐branched chiral amides with broad functional group tolerance.
High‐performance thermal insulating aerogels are attractive candidates for thermal protection in extreme environments. However, inorganic aerogels’ brittleness and poor machinability limit their ...applications, while organic aerogels suffer from severe strength degradation and structural collapse at high temperatures. Herein, for the first time, a thermo‐responsive self‐ceramifiable aerogel is demonstrated with exceptional strengthening and thermal insulation at high temperatures. This aerogel exhibits excellent toughness and processability like polymers under normal conditions but spontaneously transforms into high‐strength semi‐crystalline hard ceramics upon exposure to high temperatures. After prolonged thermal attack at 800 °C, the strength of the aerogels does not decrease but significantly increases several‐fold (from 0.739 to 2.726 MPa). The self‐ceramization behavior and mechanism of the aerogel are illustrated in detail. The unique self‐ceramifiable capacity enables aerogels to provide fire resistance, high‐strength support, and excellent thermal insulation at ultrahigh temperatures. Even with continuous burning at 1300 °C for 60 min, the 15 mm thick aerogel shows low backside temperature below 300 °C, crack‐free overall structure, and invariant porous morphology. This self‐ceramifiable aerogel opens up a new avenue for developing thermal‐protection materials with toughness, machinability, high strength, and thermal insulation in extreme environments.
A new thermo‐responsive self‐ceramifiable aerogel is for the first time reported with exceptional strengthening and thermal insulation at high temperatures. Under normal conditions, the aerogel exhibits excellent toughness and machinability. Upon exposure to high temperatures, the aerogel spontaneously and rapidly transforms into robust semi‐crystalline hard ceramics, thus leading to fire resistance, high strength, and thermal insulation in extreme environments.
We investigate the close connection between the quantum phase space Wigner distribution of small-x gluons and the color dipole scattering amplitude, and we propose studying it experimentally in the ...hard diffractive dijet production at the planned electron-ion collider. The angular correlation between the nucleon recoiled momentum and the dijet transverse momentum probes the nontrivial correlation in the phase space Wigner distribution. This experimental study not only provides us with three-dimensional tomographic pictures of gluons inside high energy protons-it gives a unique and interesting signal for the small-x dynamics with QCD evolution effects.
Pancreatic cancer (PC) is a serious malignancy with high mortality and poor prognosis due to nonspecific incipient symptoms and early metastasis. Also, increasing evidence indicates that a panel of ...genes is newly identified in the pathogenesis of PC. As is a regulatory subunit, elevated cyclin B1 (CCNB1) expression has been detected in different cancers including PC. This study is designed to investigate the effects of CCNB1 silencing on cell cycle, senescence, and apoptosis through the p53 signaling pathway in PC. PC tissues and normal pancreatic tissues were collected. Cells were transfected and assigned into different groups. The expressions of CCNB1, p53, MDM2, Bax, caspase‐9, caspase‐3, and p21 in tissues and cells were detected by reverse transcription quantitative polymerase chain reaction and western blot analysis. β‐Galactosidase staining, MTT assay, and flow cytometry were conducted to test cell senescence, proliferation, cell cycle, and apoptosis. PC tissues showed higher expressions of CCNB1 and MDM2 and lower expressions of Bax, caspase‐9, caspase‐3, and p21. Cells transfected with shCCNB1 had lower expressions of CCNB1 and MDM2, whereas higher expressions of Bax, caspase‐9, caspase‐3, p53, and p21. The shCCNB1 group had decreased proliferation and S‐phase cell proportion and increased apoptosis, senescence, and G0/G1‐phase cell proportion. The PFT‐α group showed higher expressions of MDM2 and lower expressions of Bax, caspase‐9, caspase‐3, p53, and p21. The PFT‐α group had increased proliferation and S‐phase cell proportion and declined apoptosis, senescence, and G0/G1‐phase cell proportion. CCNB1 silencing inhibits cell proliferation and promotes cell senescence via activation of the p53 signaling pathway in PC.
CCNB1 silencing inhibits cell proliferation and promotes cell senescence via activation of the p53 signaling pathway in pancreatic cancer.
Green production of NH3, especially the Li‐mediated electrochemical N2 reduction reaction (NRR) in non‐aqueous solutions, is attracting research interest. Controversies regarding the NRR mechanism ...greatly impede its optimization and wide applications. To understand the electrocatalytic process, we treated Au coated carbon fibrous paper (Au/CP) as the model catalyst. In situ XRD confirmed the transformation of lithium intermediates during NRR. Au greatly improved electron transfer kinetics to catalyze metallic Li formation, and accordingly highly accelerated spontaneous NRR. The Faradaic efficiency of NRR on Au/CP reached 34.0 %, and NH3 yield was as high as 50 μg h−1 cm−2. Our research shows that the key step of Li‐mediated non‐aqueous NRR is electrocatalytic Li reduction and offers a novel electrocatalyst design method for Li reduction.
The key step of Li‐mediated non‐aqueous NRR is electrocatalytic Li reduction. Gold greatly improved Li adsorption energy and thus highly accelerated the domino‐like nitrogen reduction reaction (NRR).
Anthocyanins are a class of water‐soluble flavonoids, which show a range of pharmacological effects, such as prevention of cardiovascular disease, obesity control and antitumour activity. Their ...potential antitumour effects are reported to be based on a wide variety of biological activities including antioxidant; anti‐inflammation; anti‐mutagenesis; induction of differentiation; inhibiting proliferation by modulating signal transduction pathways, inducing cell cycle arrest and stimulating apoptosis or autophagy of cancer cells; anti‐invasion; anti‐metastasis; reversing drug resistance of cancer cells and increasing their sensitivity to chemotherapy. In this review, the latest progress on the anticancer activities of anthocyanins and the underlying molecular mechanisms is summarized using data from basic research in vitro and in vivo, from clinical trials and taking into account theory and practice.
Linked Articles
This article is part of a themed section on Principles of Pharmacological Research of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.11/issuetoc
Gold-catalyzed intermolecular alkyne oxidation by an N-O bond oxidant has proven to be a powerful method in organic synthesis during the past decade, because this approach would enable readily ...available alkynes as precursors in generating α-oxo gold carbenes. Among those, gold-catalyzed oxidative cyclization of dialkynes has received particular attention as this chemistry offers great potential to build structurally complex cyclic molecules. However, these alkyne oxidations have been mostly limited to noble metal catalysts, and, to our knowledge, non-noble metal-catalyzed reactions such as diyne oxidations have not been reported. Herein, we disclose a copper-catalyzed oxidative diyne cyclization, allowing the facile synthesis of a wide range of valuable pyrrolo3,4-cquinolin-1-ones. Interestingly, by employing the same starting materials, the gold-catalyzed cascade cyclization leads to the divergent formation of synthetically useful pyrrolo2,3-bindoles. Furthermore, the proposed mechanistic rationale for these cascade reactions is strongly supported by both control experiments and theoretical calculations.
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