Functionalized [2.2]Paracyclophanedienes as Monomers for Poly(<i>p</i>‑phenylenevinylene)s

Poly(p-phenylenevinylene)s (PPVs) featuring complex side-chains, to date, have only been synthesized by nonliving polymerization methods which have no control over PPV molecular weights, dispersities, or end groups. [2.2]Paracyclophane-1,9-diene (pCpd) has gained attention as a monomer for its ability to be ring-opened to PPV in a living fashion. pCpd, an organic cyclic scaffold with planar chirality, has seen minimal structural diversity due to the harsh reaction conditions required to afford the highly strained compound. Herein, we introduce a general method to overcome this by targeting the synthesis of a monohydroxy-pCpd via mono-demethylation of a dialkoxy-pCpd. The monohydroxy-pCpd can then be functionalized easily, which we demonstrate using three distinct side-chains with four moieties commonly incorporated in conjugated polymers: an alkyl bromide, an oligo(ethylene glycol) chain, an enantiomerically pure side-chain, and a Boc-protected amine. These monofunctionalized-pCpds were investigated as monomers in the ring-opening metathesis polymerization (ROMP) to afford functionalized PPVs in a living manner. The functional-group-containing PPVs are synthesized with full control over their end groups, repeat units, and dispersities. The feasibility of post-polymerization modifications to incorporate any desired moiety to PPV fabricated by this method was demonstrated using an azide–alkyne click reaction. All synthesized PPVs were soluble in organic solvents and display the same fluorescent emission, indicating their conjugated backbones are unaltered

Atomistic Modeling of F‑Actin Mechanical Responses and Determination of Mechanical Properties

A molecular structural mechanics (MSM) model was developed for F-actins in cells, where the force constants describing the monomer interaction were achieved using molecular dynamics simulations. The MSM was then employed to predict the mechanical properties of F-actin. The obtained Young’s modulus (1.92 GPa), torsional rigidity (2.36 × 10^–26 Nm²), and flexural rigidity (10.84 × 10^–26 Nm²) were found to be in good agreement with existing experimental data. Subsequently, the tension-induced bending was studied for F-actins as a result of their helical structure. Mechanical instability was also investigated for the actin filaments in filopodial protrusion by considering the reinforcing effect of the actin-binding proteins. The predicted buckling load agreed well with the experimentally obtained stall force, showing a pivotal role of the actin-binding protein in regulating the stiffness of F-actin bundles during the formation of filopodia protrusion. Herein, it is expected that the MSM model can be extended to the mechanics of more complex filamentous systems such as stress fibers and actin meshwork

Two-Stage Electrical Percolation of Metal Nanoparticle–Polymer Nanocomposites

Recent experiments showed that gold nanoparticle (NP)–polymer composite exhibits excellent properties such as high stretchability and electron conductivity, rendering this novel material promising for bendable and stretchable electronics and optoelectronics. Theoretical models have been proposed to investigate the conduction mechanism; however, the role of the quantum tunneling effect in electrical percolation remains unclear. Here, we used a numerical approach together with Monte Carlo sampling to investigate the percolation of the gold NP–polymer system. The effects of the electron tunneling and the inter-NP van der Waals interaction were considered in the model. A distinct two-stage electrical percolation behavior is identified because of the effect of electron tunneling at the nanoscale. Such an effect is found to be dependent on the radii of gold NPs and becomes negligible when the radius is larger than 195 nm. The observed behavior is also sensitive to the potential barrier height of the hosting polymer. Our result therefore not only provides new insights into the conduction mechanism of the gold NP–polymer composites but also offers a new strategy for designing a metal NP–polymer system with desired properties

Large sulphur isotopic perturbations and oceanic changes during the Frasnian–Famennian transition of the Late Devonian

<p>The Frasnian–Famennian transition of the Late Devonian was one of the most critical intervals in the Phanerozoic. Sulphur isotopic pairs of carbonate-associated sulphate and pyrite sulphide from coeval sections in South China and Poland reveal frequent perturbations of sulphur cycling during this time interval. These data suggest a sudden oceanic overturn during a rapid sea-level fall probably induced by jerky block tilting in the latest Frasnian. This event was followed by long-lasting photic-zone euxinia during a rapid sea-level rise in the earliest Famennian. Large increases in continental nutrient fluxes, and subsequent primary productivity and organic burial, could have greatly enhanced bacterial sulphate reduction, producing excessive sulphide through the water columns owing to iron depletion. Subsequently, rapid ventilation of oceanic basins occurred, during which direct aerobic oxidation of sulphide into sulphate predominated in bottom waters and even surface sediments with minimal fractionation. This oxygenation was probably induced by intensive climatic cooling and/or large-scale sea-level fall. The temporal coincidence of two extinction phases with the oceanic overturn and succeeding photic-zone euxinia suggests that these extreme oceanic events played an important role in the severe biotic crisis. Furthermore, photic-zone euxinia coupled with subsequent climatic cooling may have delayed post-extinction recovery of some taxa. </p

The Effect of Z-Ligustilide on the Mobility of Human Glioblastoma T98G Cells

<div><p>Z-ligustilide (LIG), an essential oil extract from <i>Radix Angelica sinensis</i>, has broad pharmaceutical applications in treating cardio-vascular diseases and ischemic brain injury. Recently, LIG has been connected to Glioblastoma multiforme (GBM) because of its structural similarity to 3-n-alkyphthalide (NBP), which is specifically cytotoxic to GBM cells. Hence, we investigated LIG’s effect on GBM T98G cells. The study shows that LIG can significantly reduce T98G cells’ migration in a dose-dependent manner. Furthermore, the attenuation of cellular mobility can be linked to the activity of the Rho GTPases (RhoA, Rac1 and Cdc42), the three critical molecular switches governing cytoskeleton remodeling; thus, regulating cell migration. LIG significantly reduces the expression of RhoA and affects in a milder manner the expression of Cdc42 and Rac1.</p></div

Synthesis and Nonvolatile Memory Behaviors of Dioxatetraazapentacene Derivatives

Two novel heteroacenes 2,3,9,10-tetra­(furan-2-yl)-1,4,8,11-tetraaza-6,13-dioxapentacene (<b>FAOP</b>, <b>1</b>) and 2,3,9,10-tetra­(thiophen-2-yl)-1,4,8,11-tetraaza-6,13-dioxapentacene (<b>TAOP</b>, <b>2</b>) was successfully synthesized through a one-step condensation reaction, which have been fully characterized by ¹H NMR (nuclear magnetic resonance), ¹³C NMR, FT-IR (Fourier transform infrared spectroscopy), and HRMS (high-resolution mass spectrum). The sandwich-structure memory devices have been fabricated using <b>FAOP</b> (<b>1</b>) and <b>TAOP</b> (<b>2</b>) as active layers, showing a typical bipolar resistive switching (RS) behavior in positive and negative regions

Visualized Tracking and Multidimensional Assessing of Mitochondria-Associated Pyroptosis in Cancer Cells by a Small-Molecule Fluorescent Probe

Pyroptosis is closely related to the development and treatment of various cancers; thus, comprehensive studies of the correlations between pyroptosis and its inductive or inhibitive factors can provide new ideas for the intervention and diagnosis of tumors. The dysfunction of mitochondria may induce pyroptosis in cancer cells, which can be reflected by the fluctuations of the microenvironmental parameters in mitochondria as well as the changes of mitochondrial DNA level and morphology, etc. To precisely track and assess the mitochondria-associated pyroptosis process, simultaneous visualization of changes in multiphysiological parameters in mitochondria is highly desirable. In this work, we reported a nonreaction-based, multifunctional small-molecule fluorescent probe Mito-DK with the capability of crosstalk-free response to polarity and mtDNA as well as mitochondrial morphology. Accurate assessment of mitochondria-associated pyroptosis induced by palmitic acid/H2O2 was achieved through monitoring changes in mitochondrial multiple parameters with the help of Mito-DK. In particular, the pyroptosis-inducing ability of an antibiotic doxorubicin and the pyroptosis-inhibiting capacity of an anticancer agent puerarin were evaluated by Mito-DK. These results provide new perspectives for visualizing mitochondria-associated pyroptosis and offer new approaches for screening pyroptosis-related anticancer agents

LIG treatment reduced T98G single cell migration capacity.

<p><b>A</b>) Trajectories of T98G cells indicate that the presence of LIG could drastically hinder cell migration, and the addition of 0.5% IPA has a minor effect. <b>B</b>) The mean square displacement (MSD) vs. time interval is shown as a log-log plot, demonstrating that LIG treatment significantly decreases the slope of the MSD of T98G cells as compared to control conditions. The mean MSD value for each condition is plotted as a dotted black line. <b>C</b>) Histograms of the one-minute step sizes within one hour suggest a reduction of the translocation of T98G cells under LIG treatment since the occurrence of larger step sizes is greatly reduced.</p

The addition of LIG to T98G cell cultures reduced migration capacity.

<p><b>A</b>) Images of the wound-like gap closure process of T98G cells under mock, 0.5% isopropanol (IPA), 5 µM LIG, and 25 µM LIG (top to bottom) are presented at the 0^th, 8^th and 14^th hour. The yellow lines indicate the approximate boundary between cell-inhabited and cell-free (central) regions of each image. Scale bar: 200 µm. <b>B</b>) The result of a quantitative analysis of the gap closure of T98G cells under no treatment, 0.5% IPA, and 4 concentrations (2.5, 5, 15 and 25 µM) of LIG treatment is shown. The gap index is the percentage of original wound gap that remains cell-free. The data are the mean gap index results of 6 experiments with error bars representing the standard deviation (also refer to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0066598#pone.0066598.s001" target="_blank">Fig. S1</a>).</p