SciCombinator

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We find that conjugated polymers can undergo reversible structural phase transitions during electrochemical oxidation and ion injection. We study poly[2,5-bis(thiophenyl)-1,4-bis(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)benzene] (PB2T-TEG), a conjugated polymer with glycolated side chains. Using grazing incidence wide angle X-ray scattering (GIWAXS), we show that, in contrast to previously known polymers, this polymer switches between two structurally distinct crystalline phases associated with electrochemical oxidation/reduction in an aqueous electrolyte. Importantly, we show that this unique phase change behavior has important physical consequences for ion-polaron pair transport. Notably, using moving front experiments visualized by both optical microscopy and super-resolution photoinduced force microscopy (PiFM), we show that a laterally-propagating ion-polaron pair front in PB2T-TEG exhibits non-Fickian transport, retaining a sharp step-edge profile, in stark contrast to the Fickian diffusion more commonly observed in polymers like P3MEEMT. This structural phase transition is reminiscent of those accompanying ion uptake in inorganic materials like LiFePO4. We propose that engineering similar properties in future conjugated polymers may enable the realization of new materials with superior performance in electrochemical energy storage or neuromorphic memory applications.

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The adsorption properties and microscopic mechanism of CO2 adsorption in 1,1-dimethyl-1,2-ethylenediamine (dmen) functionalized M2(dobpdc) (dobpdc4-=4,4'- dioxidobiphenyl-3,3'-dicarboxylate; M=Mg, Sc-Zn) have been completely unveiled for the first time via comprehensive investigations based on the first-principles density functional theory (DFT) calculations. The results show that for the primary-primary amine, dmen prefers to interact with the open metal site of M2(dobpdc) via the end with smaller steric hindrance. The binding energies of dmen with MOFs are in the range of 104-174 kJ/mol. In presence of CO2, it fully inserts into the metal-N bond, forming ammonium carbamate. The CO2 binding energies vary from 53 to 89 kJ/mol, showing strong metal dependence. Among the eleven metals, dmen-Sc2(dobpdc) and dmen-Mg2(dobpdc) have highest CO2 binding energies of 89 and 84 kJ/mol, respectively, which may have large CO2 adsorption capacity for practical applications. More importantly, the microscopic CO2 capture process of dmen-M2(dobpdc) is revealed at the atomic level. The whole reaction process includes two steps, i.e. formation of zwitterion intermediate (step1) and rearrangement of the zwitterion intermediate (step2). The first step in which nucleophilic addition between CO2 and the metal-bound amine and proton transfer from the metal-bound amine to free amine simultaneously occur, is rate-determining step, with higher energy barriers (0.99-1.35 eV). The second step with much lower barriers (maximum of 0.16 eV) is extremely easy, which can promote the whole CO2 uptake process in dmen-M2(dobpdc). This study provides fundamental understanding the underlying mechanism of rather complicated CO2 adsorption process and shed important insights on design, synthesis and optimization of highly efficient CO2 capture materials.

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High-throughput in vitro reporter gene assays are increasingly applied to assess the potency of chemicals to alter specific cellular signaling pathways. Genetically modified reporter gene cell lines provide stable readouts of the activation of cellular receptors or transcription factors of interest, but such reporter gene assays have been criticized for not capturing cellular metabolism. We characterized the metabolic activity of the widely applied AREc32 (human breast cancer MCF-7), ARE-bla (human liver cancer HepG2), and GR-bla (human embryonic kidney HEK293) reporter gene cells in absence and in presence of benzo(a)pyrene (BaP), an AhR ligand known to upregulate cytochrome P450 in vitro and in vivo. We combined fluorescence microscopy with chemical analysis, real-time PCR, and EROD activity measurements to track temporal changes in BaP and its metabolites in the cells and surrounding medium over time in relation to the expression and activity of metabolic enzymes. Decreasing BaP concentrations and formation of metabolites agreed with the high basal CYP1 activity of ARE-bla and the strong CYP1A1 mRNA induction in AREc32, whereas BaP concentrations were constant in GR-bla, in which neither metabolites nor CYP1 induction were detected. The study emphasizes that differences in sensitivity between reporter gene assays may be caused not only by different reporter constructs but also by a varying biotransformation rate of the evaluated parent chemical. The basal metabolic capacity of reporter gene cells in absence of chemicals is not a clear indication because we demonstrated that the metabolic activity can be upregulated by AhR ligands during the assay. The combination of methods presented here is suitable to characterize the metabolic activity of cells in vitro and can improve the interpretation of in vitro reporter gene effect data and extrapolation to in vivo human exposure.

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COVID-19 is a new entity in the field of clinical medicine. In near future, anesthesiologists around the globe increasingly will encounter patients who need surgery and at the same time are suspected or confirmed cases of COVID-19. Planning for a safe anesthesia technique is inevitable.

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The expression level and subcellular distribution of messenger RNA (mRNA) dynamically changed during the different cell circles. Spatiotemporally controllable signal amplification methods capable of controlling the when and where of the amplification process could allow the sensitive mRNA imaging of selected living cells at dictated time-intervals of the cell life-cycle. However, the present methods for amplified mRNA imaging are hard to control the where and when of the signal amplification due to the lack of effective strategy to precisely trigger and control the signal amplification process. Herein, we present a conceptual study termed as photocontrollable nucleic acid cascade recycling amplification which uses near-infrared (NIR) light to precisely control and trigger the whole process. This strategy is achieved by integrating photocontrollable nucleic acid displacement reaction with exonuclease III (EXO III) assisted nucleic acid cascade recycling amplification and combination with upconversion nanoparticles (UCNPs), thus resulting in a NIR light activatable signal amplification. As a proof of concept, we demonstrate this developed NIR light triggered signal amplification process in selected living cancer cells for spatiotemporally controllable signal amplified mRNA imaging.

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The decyanation of secondary aliphatic nitriles and the twofold decyanation of malononitriles leading to alkanes in the presence of 1,3-dimethylimidazol-2-ylidene borane (diMeImd-BH3) are reported. These reactions proceed via a radical mechanism that involves the addition of a borane radical anion to the nitrile to form an iminyl radical, followed by cleavage of a carbon-carbon bond. Theoretical calculations suggest that the β-cleavage of these iminyl radicals, which affords NHC-BH2CN and the corresponding alkyl radicals, is the rate-determining step in this reaction.

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Spinal muscle atrophy (SMA) is the leading genetic cause of infant mortality. SMA originates from the loss of functional survival motor neuron (SMN) protein. In most SMA cases the SMN1 gene is deleted. However, in some cases SMN is mutated, impairing its biological functions. SMN mutants could provide clues about the biological functions of SMN and specific impact on SMA, potentially leading to the identification of new pathways and thus providing novel treatment alternatives, and even personalized care. Here, we discuss the biochemistry of SMN and the most recent SMA treatment strategies.

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Threshold collision-induced dissociation (TCID) of Th(OH)3+(H2O)n (n = 1 - 4) with xenon was performed using a guided ion beam tandem mass spectrometer (GIBMS). The primary dissociation pathway for all complexes is a loss of a single water molecule followed by the sequential loss of additional water molecules at higher collision energies. The data were analyzed using a statistical model after accounting for lifetime effects and reactant internal and kinetic energy distributions to obtain 0 K bond dissociation energies (BDEs). These were also converted using rigid rotor/harmonic oscillator approximations to yield thermodynamic values at room temperature. The 0 K BDEs of H2O ligands to Th(OH)3+ (IV) are experimentally determined for the first time as 106 ± 6, 89 ± 6, 76 ± 4, and 51 ± 4 kJ/mol for the first, second, third, and fourth water ligand added. These values agree reasonably well with values calculated at the B3LYP, B3PW91, and PBE0 levels of theory with cc-pVQZ basis sets, whereas B3LYP-GD3BJ and MP2 single point energies systematically overestimate the bond energies by about 20 and 25 kJ/mol, respectively.

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Wings of insects exhibit many functions apart from flying. In particular, their anti-reflection function is important for insects to avoid detection by their enemies. This function can be applied to anti-reflection bio-mimetic films in engineering fields. For such applications, confirming the anti-reflection mechanisms of insect wings is important. Herein, we used electron microscopy to compare the surfaces of green lacewing wings with and without a surface wax structure and recorded the transmittance spectra to clarify the surface structural and optical properties of insect wings. The spectral transmittance was higher for wings with a surface wax structure than for wings without a wax layer in the light wavelength regime from 500 to 750~nm. We constructed a concise model of the green lacewing wing with flake-like surface structure with a graded effective refractive index corresponding to the wing samples with a surface wax layer; we also constructed a simple thin-film model corresponding to the wing samples without a wax layer. The graded refractive indices were calculated using the effective medium theory, and the transmittance spectra of such models were then calculated using the transfer-matrix method. It was observed that the calculated spectra are in good agreement with the experimental results. In addition, wing samples without a surface structure induce thin-film interference. These results suggest that a wax structure can reduce the reflectance and increase the transmittance enabling the green lacewings to avoid detection by their enemies. These findings may lead to further advances in both the bio-mimetic field and fundamental research fields.

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Two-dimensional (2D) Janus structures, which are totally different from prevailing 2D structures, are more interesting for the photocatalytic water splitting. Here we proposed some inartificial 2D Ge4Se9 Janus structures. Excellent photocatalytic properties are revealed: (a) Ge4Se9 structures exhibit layer independent direct-gap character with appropriate band gaps of 2.53, 2.22, 2.11 and 2.03 eV for monolayered, bilayered, tripled and four-layered ones, respectively; (b) Band edge positions of these 2D structures are suitable for the driving of evolution reaction of water splitting; © More importantly, owning to intrinsic electric polarization, charge densities of valence band maximum (VBM) and conduction band minimum (CBM) of tripled and four-layered Ge4Se9 structures can be notably separated; (d) In addition, we also observed that these 2D structures can possess rather pronounced optical absorption under the visible light region. This work discloses some inartificial 2D Janus structures, whose fascinating properties render them as promising photocatalysts for water splitting.