Diazoacetate polymerization has attracted considerable research attention because it is an effective approach for fabricating carbon-carbon (C-C) main chain polymers. However, diazoacetate ...polymerization based on inexpensive catalysts has been a long-standing challenge. Herein, we report a Ni(II) catalyst that can promote the living polymerization of various diazoacetates, yielding well-defined C-C main chain polymers, polycarbenes, with a predictable molecular weight (M
) and low dispersity (M
/M
). Moreover, the Ni(II)-catalyzed sequential living polymerization of thiophene and diazoacetate monomers affords interesting π-conjugated poly(3-hexylthiophene)-block-polycarbene copolymers in high yields with a controlled M
, variable compositions, and low M
/M
, although the structure and polymerization mechanism of the two monomers differ. Using this strategy, amphiphilic block copolymers comprising hydrophobic poly(3-hexylthiophene) and hydrophilic polycarbene blocks are facilely prepared, which were self-assembled into well-defined supramolecular architectures with tunable photoluminescence.
Developing high performance and environment‐friendly fluoropolymers is greatly desired. In this work, we found that 2‐diazo‐1,1,1‐trifluoroethane can be polymerized by air‐stable alkyne‐palladium(II) ...catalysts following a living polymerization mechanism, affording a fluoropolymer, poly(trifluoromethyl methylene) in high yield with controlled molar mass and low dispersity. This polymer bears trifluoromethyl on every main chain atom and thus has good resistance to chemical corrosion, high hydrophobicity, and excellent dielectric constant with low dielectric loss. Due to the steric hindrance between the trifluoromethyl pendants, the synthetic poly(trifluoromethyl methylene) can twist into a stable helix. The one‐handed preferred helices synthesized using chiral PdII‐catalysts exhibit high optical activity and circularly polarized luminescence. Remarkably, such polymer can be completely degraded to (E)‐1,1,1,4,4,4‐hexafluorobut‐2‐ene at high temperatures (>280 °C). Additionally, taking advantage of the living chain end, the polymer can be further modified.
Living polymerization of 2‐diazo‐1,1,1‐trifluoroethane gives environmental friendly poly(trifluoromethylmethylene) in high yield with controllable molar mass and low dispersity, which twisted into stable helix with clear circularly polarized luminescence. The high fluorine content results in high hydrophobicity, good resistance to chemical corrosion, high dielectric constant with low dielectric loss.
Lactate is a prominent energy substrate for oxidative tumor cells. Interfering with the lactate‐fueled respiration of oxidative tumor cells would be a promising therapeutic strategy for cancer ...treatment. In this study, α‐cyano‐4‐hydroxycinnamate (CHC) is incorporated into a porous Zr (IV)‐based porphyrinic metal‐organic framework (PZM) nanoparticle, to reduce the lactate uptake by inhibiting the expression of lactate‐proton symporter, monocarboxylate transporter 1 (MCT1) in tumor cells, thus transform lactate‐fueled aerobic respiration to anaerobic glycolysis. The alteration in energy supply can also decrease the oxygen consumption in tumor cells, which would facilitate the photodynamic therapy (PDT) in cancer treatment. Moreover, hyaluronic acid (HA) is coated on the surface of PZM nanoparticles for CD44‐targeting and hyaluronidase‐induced intracellular drug releasing. Both in vitro and in vivo studies confirmed good biocompatibility and enhanced PDT efficacy of the HA‐coated PZM nanoparticles (CHC‐PZM@HA) in tumor cells. The CHC‐PZM@HA platform will provide a new perspective in cancer therapy.
Enhanced photodynamic therapy (PDT) by inhibiting lactate uptake. Hyaluronic acid modified porphyrinic metal‐organic framework nanoparticles delivered MCT1 inhibitor into cancer cells. With the releasing of loaded drugs by enzymatic degradation, the aerobic respiration of lactate is disturbed and intratumoral oxygen pressure is upregulated. The nanocarrier system significant enhances the anticancer effect of PDT.
In this work, air-stable palladium(II) catalysts bearing bidentate phosphine ligands were designed and prepared, which could initiate fast and living polymerizations of various diazoacetate monomers ...under mild conditions. The polymerization afforded the desired polymers in high yields with controlled molecular weights (M ns) and narrow molecular weight distributions (M w/M ns). The M ns of the isolated polymers were linearly correlated to the initial feed ratios of monomer to catalyst, confirming the living/controlled manner of the polymerizations. The M n also increased linearly with the monomer conversion, and all of the isolated polymers showed narrow M w/M ns. The polymerization was relatively fast and could be accomplished within several minutes. Such fast living polymerization method can be applied to a wide range of diazoacetate monomers in various organic solvents at room temperature in air. Taking advantage of the living nature, we facilely prepared a series of block copolymers through chain extension reactions. The amphiphilic block copolymers synthesized by this method exhibited interesting self-assembly properties. Moreover, polymerization of achiral bulky diazoacetate by Pd(II) catalysts bearing a chiral bidentate phosphine ligand leads to the formation of polymers with high optical activity due to the formation of the predominantly one-handed helix of the main chain. The helix sense of the polymers was determined by the chirality of the Pd(II) catalysts.
Self‐sorting plays a crucial role in living systems such as the selective assembly of DNA and specific folding of proteins. However, the self‐sorting of artificial helical polymers such as ...biomacromolecules has rarely been achieved. In this work, single‐handed helical poly(phenyl isocyanide)s bearing pyrene (Py) and naphthalene (Np) probes were prepared, which exhibited interesting self‐sorting properties driven by both helicity and molecular weight (Mn) in solution, solid state, gel, and on the gel surface as well. The polymers with the same helix sense and similar Mn can self‐sort and assemble into well‐defined two‐dimensional smectic architectures and form stable gels in organic solvents. In contrast, mixed polymers with opposite handedness or different Mn were repulsive to each other and did not aggregate. Moreover, the gels of helical polymers with the same handedness and similar Mn can recognize themselves and adhere together to form a gel.
Single‐handed helical polymers can recognize themselves by discrimination of their helicity and molecular weight, and further self‐assemble into well‐defined two‐dimensional smectic architectures. Moreover, gels formed from the helical polymers can also recognize themselves based on helicity and molecular weight and can selectively adhere together to form one gel.
ABSTRACT
Autophagy is an evolutionarily conserved degradation pathway in eukaryotes; it plays a critical role in nutritional stress tolerance. The circadian clock is an endogenous timekeeping system ...that generates biological rhythms to adapt to daily changes in the environment. Accumulating evidence indicates that the circadian clock and autophagy are intimately interwoven in animals. However, the role of the circadian clock in regulating autophagy has been poorly elucidated in plants. Here, we show that autophagy exhibits a robust circadian rhythm in both light/dark cycle (LD) and in constant light (LL) in Arabidopsis. However, autophagy rhythm showed a different pattern with a phase‐advance shift and a lower amplitude in LL compared to LD. Moreover, mutation of the transcription factor LUX ARRHYTHMO (LUX) removed autophagy rhythm in LL and led to an enhanced amplitude in LD. LUX represses expression of the core autophagy genes ATG2, ATG8a, and ATG11 by directly binding to their promoters. Phenotypic analysis revealed that LUX is responsible for improved resistance of plants to carbon starvation, which is dependent on moderate autophagy activity. Comprehensive transcriptomic analysis revealed that the autophagy rhythm is ubiquitous in plants. Taken together, our findings demonstrate that the LUX‐mediated circadian clock regulates plant autophagy rhythms.
Plant autophagy displays robust circadian rhythms in light/dark cycles and constant light. The core circadian clock component LUX ARRHYTHMO contributes to the circadian rhythm of autophagy by transcriptionally repressing autophagy‐related genes.
Abstract
Bound states in the continuum (BICs) are resonant modes of open structures that do not suffer damping, despite being compatible with radiation in terms of their momentum. They have been ...raising significant attention for their intriguing topological features, and their opportunities in photonics to enhance light-matter interactions. In parallel, the coherent excitation of optical devices through the tailored interference of multiple beams has been explored as a way to enhance the degree of real-time control over their response. Here, we leverage the combination of these phenomena, and exploit the topological features of BICs in the presence of multiple input beams to enable full polarization control on the entire Poincaré sphere in a photonic crystal slab only supporting a symmetry-protected BIC, experimentally demonstrating highly efficient polarization conversion controlled in real time through the superposition of coherent excitations. Our findings open exciting opportunities for a variety of photonic and quantum optics applications, benefitting from extreme wave interactions and topological features around BICs combined with optical control through coherent interference of multiple excitations.
Facile synthesis of high optically active helical polymers from achiral monomers still remains a great challenge. In this work, two chiral Ni(II) catalysts bearing chiral R- or S-2a ligands were ...facilely prepared which can efficiently initiate the living/controlled polymerization of allene monomers and afford well-defined polyallenes in high yields with controlled molecular masses (M ns) and low molecular mass distributions (M w/M ns). The catalysts showed interesting regioselectivity on the cumulated double bonds of allene monomers, as the polymerizations were highly selective which occurred on 2,3-double bonds. Moreover, the polymerization of achiral allene monomers using chiral Ni(II) catalysts showed remarkable helix-sense selectivity. The yielded polyallenes exhibited high optical activity due to the formation of a predominant one-handed helix as revealed by circular dichroism, UV–vis, and direct atomic force microscopy (AFM) observations as well. The predominant one-handed helicity of the generated polyallenes was solely determined by the chirality of the Ni(II) catalysts.
Abstract
Recent ground-based observations of TeV photons have significantly deepened our understanding of the nature of gamma-ray bursts (GRBs). However, many fundamental problems remain unsolved ...concerning the physical mechanisms behind GRBs, necessitating the need for sufficient statistical data. The High Altitude Detection of Astronomical Radiation (HADAR) experiment utilizes a wide-angle water Cherenkov telescope, presenting a novel approach to measure the spectra and variability of GRBs from 10 GeV to 10 TeV energy ranges with unprecedented photon statistics and thereby break new ground in elucidating the physics of GRBs, which is still poorly understood. In this study, a time-dependent numerical modeling technique is utilized to simulate extensive light curves and spectral energy distributions of synthetic GRB afterglow emissions. By harnessing the remarkable capabilities of HADAR, we evaluate its potential in detecting GRB afterglow emissions at energies >10 GeV. Through our analysis, we unveil the prospect of detecting an estimated 5.8 GRBs annually, facilitating a systematic investigation into their reliance on model parameters. Future HADAR observations would offer valuable insights into the magnetic field and the environmental conditions surrounding GRBs.
Expansins, a group of cell wall-loosening proteins, are involved in cell-wall loosening and cell enlargement in a pH-dependent manner. According to previous study, they were involved in plant growth ...and abiotic stress responses. However, information on the biological function of the expansin gene in moso bamboo is still limited. In this study, we identified a total of 82 expansin genes in moso bamboo, clustered into four subfamilies (α-expansin (EXPA), β-expansin (EXPB), expansin-like A (EXLA) and expansin-like B (EXPB)). Subsequently, the molecular structure, chromosomal location and phylogenetic relationship of the expansin genes of
(
were further characterized. A total of 14 pairs of tandem duplication genes and 31 pairs of segmented duplication genes were also identified, which may promote the expansion of the expansin gene family. Promoter analysis found many cis-acting elements related to growth and development and stress response, especially abscisic acid response element (ABRE). Expression pattern revealed that most
have tissue expression specificity. Meanwhile, the expression of some selected
was significantly upregulated mostly under abscisic acid (ABA) and polyethylene glycol (PEG) treatment, which implied that these genes actively respond to expression under abiotic stress. This study provided new insights into the structure, evolution and function prediction of the expansin gene family in moso bamboo.
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