Viologens (1,1’‐disubstituted 4,4’‐bipyridyls) possessing electron‐deficient properties and redox activity are a class of suitable chromophores to assemble metal–organic hybrid photochromic ...materials. Thus, viologen‐functionalized metal–organic frameworks (MOFs) have attracted much attention for their photochromic properties; however, the syntheses of lanthanide‐viologen hybrid crystalline photochromic materials still face many challenges. For example, the structures and properties of the final products are difficult to predict and are limited by molecular configurations. In this work, host‐guest composite‐material Ln‐NH2BDC‐pbpy MOFs were constructed by encapsulating viologen derivative pbpyCl2. The pbpy2+ moieties are uniformly embed by their π‐π conjugation in the pores of the 3D structure by electrostatic interactions. Due to the encapsulation of the chromophore pbpy2+ moieties, Ln‐NH2BDC‐pbpy MOFs have reversible photochromic properties: they can change color after irradiation and can return to the original color after being protected from light or heating. Interestingly, the fluorescence intensity decreases with illumination time and recovers in the dark. As a result, Ln‐NH2BDC‐pbpy MOFs show both photochromic and photomodulated fluorescence. Based on the outstanding fluorescence performance of the Ln‐NH2BDC‐pbpy MOFs, they also show a wonderful effect for detecting nitrophenols, especially TNP.
Six novel 3D Ln‐NH2BDC MOFs encapsulating pbpyCl2 have been designed and synthesized. They are sensitive to visible light and exhibit a good reversible photochromic and photomodulated fluorescence phenomena. Moreover, they have a good detection effect on nitrophenols, especially 2,4,6‐trinitrophenol (TNP).
All‐natural materials derived from cellulose nanofibers (CNFs) are expected to be used to replace engineering plastics and have attracted much attention. However, the lack of crack extension ...resistance and 3D formability of nanofiber‐based structural materials hinders their practical applications. Here, a multiscale interface engineering strategy is reported to construct high‐performance cellulose‐based materials. The sisal microfibers are surface treated to expose abundant active CNFs with positive charges, thereby enhancing their interfacial combination with the negatively charged CNFs. The robust multiscale dual network enables easy molding of multiscale cellulose‐based structural materials into complex 3D special‐shaped structures, resulting in nearly twofold and fivefold improvements in toughness and impact resistance compared with those of CNFs‐based materials. Moreover, this multiscale interface engineering strategy endows cellulose‐based structural materials with better comprehensive performance than petrochemical‐based plastics and broadens cellulose's potential for lightweight applications as structural materials with lower environmental effects.
A high‐performance multiscale cellulose‐based structural material is constructed through a multiscale interface engineering strategy. The positive and negative charges treatment of microfibers and nanofibers effectively solves the interface bonding problem in multiscale design, and allows them to be easily shaped into complex three‐dimensional special‐shaped structures. This sustainable material offers superior mechanical and thermal properties compared to petrochemical‐based plastics.
Autophagy is a dynamic and highly regulated process of self-digestion responsible for cell survival and reaction to oxidative stress. As oxidative stress is increased in uremia and is associated with ...vascular calcification, we studied the role of autophagy in vascular calcification induced by phosphate. In an in vitro phosphate-induced calcification model of vascular smooth muscle cells (VSMCs) and in an in vivo model of chronic renal failure, autophagy was inhibited by the superoxide dismutase mimic MnTMPyP, superoxide dismutase-2 overexpression, and by knockdown of the sodium-dependent phosphate cotransporter Pit1. Although phosphate-induced VSMC apoptosis was reduced by an inhibitor of autophagy (3-methyladenine) and knockdown of autophagy protein 5, calcium deposition in VSMCs was increased during inhibition of autophagy, even with the apoptosis inhibitor Z-VAD-FMK. An inducer of autophagy, valproic acid, decreased calcification. Furthermore, 3-methyladenine significantly promoted phosphate-induced matrix vesicle release with increased alkaline phosphatase activity. Thus, autophagy may be an endogenous protective mechanism counteracting phosphate-induced vascular calcification by reducing matrix vesicle release. Therapeutic agents influencing the autophagic response may be of benefit to treat aging or disease-related vascular calcification and osteoporosis.
Abstract
Stone cells negatively affect fruit quality because of their firm and lignified cell walls, so are targets for reduction in pear breeding programmes. However, there is only limited knowledge ...of the molecular mechanisms underlying the formation of stone cells. Here, we show that PbrMYB169, an R2R3 MYB transcription factor, of Pyrus bretschneideri positively regulates lignification of stone cells in pear fruit. PbrMYB169 was shown to be co-expressed with lignin biosynthesis genes during pear fruit development, and this co-expression pattern was coincident with stone cell formation in the fruit of Pyrus bretschneideri 'Dangshansuli'. The PbrMYB169 expression level was also positively correlated with stone cell content in 36 pear cultivars tested. PbrMYB169 protein significantly activated the promoter of lignin genes C3H1, CCR1, CCOMT2, CAD, 4CL1, 4CL2, HCT2, and LAC18 via binding to AC elements ACC(T/A)ACC in these promoters. Furthermore, overexpression of PbrMYB169 in transgenic Arabidopsis plants enhanced the expression of lignin genes, and increased lignin deposition and cell wall thickness of vessel elements, but did not change the ratio of syringyl and guaiacyl lignin monomers. In conclusion, PbrMYB169 appears to be a transcriptional activator of lignin biosynthesis and regulates secondary wall formation in fruit stone cells. This study advances the understanding of the regulation of lignin biosynthesis and provides valuable molecular genetic information for reducing stone cell content in pear fruit.
PbrMYB169 has been shown to positively regulate lignification of stone cells in pear fruit via activating the promoter of lignin genes C3H1, CCR1, CCOMT2, CAD, 4CL1, 4CL2, HCT2, and LAC18.
The exploration of extreme environments has become necessary for understanding and changing nature. However, the development of functional materials suitable for extreme conditions is still ...insufficient. Herein, a kind of nacre‐inspired bacterial cellulose (BC)/synthetic mica (S‐Mica) nanopaper with excellent mechanical and electrical insulating properties that has excellent tolerance to extreme conditions is reported. Benefited from the nacre‐inspired structure and the 3D network of BC, the nanopaper exhibits excellent mechanical properties, including high tensile strength (375 MPa), outstanding foldability, and bending fatigue resistance. In addition, S‐Mica arranged in layers endows the nanopaper with remarkable dielectric strength (145.7 kV mm−1) and ultralong corona resistance life. Moreover, the nanopaper is highly resistant to alternating high and low temperatures, UV light, and atomic oxygen, making it an ideal candidate for extreme environment‐resistant materials.
A nacre‐inspired nanopaper is fabricated through an aerosol‐assisted biosynthesis (AABS) strategy. Based on the AABS strategy and biomimetic structure design, the nanopaper has excellent mechanical properties, high dielectric strength, and ultralong corona resistance time. The dielectric‐mechanical comprehensive performance of the nanopaper is far beyond that of various commercial mica papers.
As the key intermediate phase of crystalline calcium carbonate biominerals, amorphous calcium carbonate (ACC) remains mysterious in its structures because of its long‐range disorder and instability. ...We herein report the synthesis of ACC nanospheres in a water‐deficient organic solvent system. The obtained ACC nanospheres are very stable under dry conditions. Cryo‐TEM reveals that each nanospheres consists of smaller nanosized clusters. We further demonstrate that these clusters can precipitate on other substrates to form an ultrathin ACC coating, which should be an ACC cluster monolayer. The results demonstrate that the presence of small ACC clusters as the subunits of larger aggregates is inherent to ACC synthesized in water‐alcohol system but not induced by polymer additives.
Amorphous calcium carbonate(ACC) nanoparticles are synthesized in water‐deficient ethanol solution. The nanoparticles consist of tiny clusters as revealed by cryo‐TEM. ACC can aggregate on templates such as graphene oxide nanosheets. These findings provide a theoretical basis for controlled synthesis of ACC and a strategy to fabricate ultrathin mineral coatings on different substrates.
The utilization of wide bandgap devices such as silicon carbide (SiC) diode and mosfet can significantly increase the power density and the efficiency of rectifier circuits. However, SiC-based ...circuits always suffer from the high cost of their power stage. In this paper, a highly efficient low-cost hybrid three-phase three-level rectifier is proposed. Instead of using SiC diode and Si IGBT, it consists of SiC mosfet and Si diode. It presents extremely low switching losses because the reverse recovery losses of all the Si diodes are eliminated. At the same time, the total device cost of this rectifier is much lower than the all-SiC-based rectifiers. Furthermore, half-bridge modules can be used to comprise the rectifier circuit, which makes it suitable for high-power applications. In this paper, the circuit operational analysis, simulation, and experimental results are given. A comparison is given to show the advantages of the proposed rectifier.
Nickel-catalyzed asymmetric hydrogenation of challenging tetrasubstituted fluorinated enamides has been achieved, affording chiral α-fluoro-β-amino esters in high yields with excellent diastereo- and ...enantioselectivities (up to 98% yield, >99 : 1 dr, up to >99% ee). Deuterium-labeling experiments and control experiments were conducted to probe the mechanism, and the results indicated that the acidity of the solvent plays a critical role in the control of diastereoselectivity by trapping the adduct of nickel hydride to Cdouble bond, length as m-dashC bonds
protonolysis, giving the hydrogenation product with stereospecific
-selectivity. This protocol provides efficient access to chiral α-fluoro-β-amino esters which have important potential applications in organic synthesis and medicinal chemistry.
In this research, resveratrol (RSV)‐loaded scaffolds have been prepared to control the release of resveratrol and used to delay hepatic stellate cell (HSC) senescence in vitro. The functional ...carboxyl group–COOH is first introduced to the surface of poly(ε‐caprolactone/d,l‐lactide) (P(CL‐DLLA)) under the coadministration of ultra‐violet (UV) treatment and photo initiator and then resveratrol are conjugated onto the surface of the modified scaffolds through esterification. The characterization of the structure of RSV‐AA‐P(CL‐DLLA) shows that resveratrol has been successfully conjugated onto the modified surface. Cell growth exhibits a higher level of cell viability and much more obvious agglomeration on the surface of the synthetic RSV‐AA‐P(CL‐DLLA). Meanwhile the activity of senescence‐associated β‐galactosidase (SA‐β‐gal) and reactive oxygen species (ROS) is downgulated for cells on RSV‐AA‐P(CL‐DLLA), which suggests that cell senescence is delayed on RSV‐AA‐P(CL‐DLLA). And then it is attested that cells have a lower level of p53 but SIRT1 expression is upregulated on RSV‐AA‐P(CL‐DLLA), which might be related to resveratrol release from RSV‐AA‐P(CL‐DLLA). It also suggested cell senescence on RSV‐AA‐P(CL‐DLLA) has been regulated by p53 and the SIRT1 signaling pathway. In all, the present study shows that RSV‐AA‐P(CL‐DLLA) can be successfully prepared to promote cell growth and delay cell senescence and could be used for cell‐based therapy in tissue engineering.
RSV‐AA‐P(CL‐DLLA) is fabricated with the introduction of the functional carboxyl group–COOH) onto the surface of poly(ε‐caprolactone/d,l‐lactide) P(CL‐DLLA)) and esterification of resveratrol with the modified surface. The synthetic scaffold is used to delay cell senescence in cell‐based therapy tissue engineering.
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