Synthesis and Star/Linear Topology Transformation of a Mechanically Linked ABC Terpolymer

The synthesis of an ABC star terpolymer containing one polymer chain connected mechanically through a rotaxane linkage and its topology transformation to a linear structure are reported. Pseudo[2]­rotaxane, which was designed as the key trifunctional species for the star polymer synthesis, comprised a <i>sec</i>-ammonium axle with ethynyl and hydroxy groups and a crown ether wheel with a trithiocarbonate group. Stepwise polymer connections to the pseudo[2]­rotaxane using the three groups afforded a rotaxane-linked ABC star terpolymer. The topology transformation from star to linear by the removal of the attractive interaction between the axle and wheel components yielded a linear ABC terpolymer via the wheel shifting to the axle end. The spectroscopic and solution property changes clearly indicated the occurrence of the polymer topology change

Iron-Catalyzed Remote Arylation of Aliphatic C–H Bond via 1,5-Hydrogen Shift

Catalytic amounts of an iron­(III) salt and a N-heterocyclic carbene ligand catalyze the arylation of 2-iodoalkylarenes with diphenylzinc selectively at the γ C–H bond of the alkyl side chain. Several lines of evidence suggest that the iron catalyst reacts with the aryl iodide moiety of the substrate to generate an aryliron intermediate that behaves in a radical manner and cleaves the aliphatic C–H bond through 1,5-hydrogen transfer; the resulting alkyliron intermediate undergoes reductive elimination to give the arylated product

Diols, α‑Ketols, and Diones as 2_2π Components in [2+2+2] Cycloadditions of 1,6-Diynes via Ruthenium(0)-Catalyzed Transfer Hydrogenation

The first use of vicinal diols, ketols, or diones as 2_2π components in metal-catalyzed [2+2+2] cycloaddition is described. Using ruthenium(0) catalysts, 1,6-diynes form ruthena­cyclo­penta­dienes that engage transient diones in successive carbonyl addition. Transfer hydrogenolysis of the resulting ruthenium­(II) diolate mediated by the diol or ketol reactant releases the cycloadduct with regeneration of ruthenium(0) and the requisite dione

Osmium(0)-Catalyzed C–C Coupling of Ethylene and α‑Olefins with Diols, Ketols, or Hydroxy Esters via Transfer Hydrogenation

Osmium­(0) complexes derived from Os₃(CO)₁₂ and XPhos (2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl) catalyze the C–C coupling of α-hydroxy esters <b>1a</b>–<b>1i</b>, α-ketols <b>1j</b>–<b>1o</b>, or 1,2-diols <i>dihydro</i>-<b>1j</b>–<b>1o</b> with ethylene <b>2a</b> to form ethylated tertiary alcohols <b>3a</b>–<b>3o</b>. As illustrated in couplings of 1-octene <b>2b</b> with vicinally dioxygenated reactants <b>1a</b>, <b>1b</b>, <b>1i</b>, <b>1j</b>, <b>1k</b>, <b>1m</b>, higher α-olefins are converted to adducts <b>4a</b>, <b>4b</b>, <b>4i</b>, <b>4j</b>, <b>4k</b>, <b>4m</b> with complete levels of branched regioselectivity. Oxidation level independent C–C coupling is demonstrated by the reaction of 1-octene <b>2b</b> with diol <i>dihydro</i>-<b>1k</b>, α-ketol <b>1k</b>, and dione <i>dehydro</i>-<b>1k</b>. Functionalized olefins <b>2c</b>–<b>2f</b> react with ethyl mandelate <b>1a</b> to furnish adducts <b>5a</b>–<b>8a</b> as single regioisomers. The collective data, including deuterium labeling studies, are consistent with a catalytic mechanism involving olefin–dione oxidative coupling to form an oxa-osmacyclopentane, which upon reductive cleavage via hydrogen transfer from the secondary alcohol reactant releases the product of carbinol <i>C</i>-alkylation with regeneration of the ketone. Single-crystal X-ray diffraction data of the dinuclear complex Os₂(CO)₄(O₂CR)₂(XPhos)₂ and the trinuclear complex Os₃(CO)₁₁(XPhos) are reported. These studies suggest increased π-backbonding at the stage of the metal–olefin π-complex plays a critical role in facilitating alkene–carbonyl oxidative coupling, as isostructural ruthenium(0) complexes, which are weaker π-donors, do not catalyze the transformations reported herein

Epithelial-Mesenchymal Transition Stimulates Human Cancer Cells to Extend Microtubule-based Invasive Protrusions and Suppresses Cell Growth in Collagen Gel

<div><p>Epithelial-mesenchymal transition (EMT) is a crucial event in tumor invasion and metastasis. However, most of past EMT studies have been conducted in the conventional two-dimensional (2D) monolayer culture. Therefore, it remains unclear what invasive phenotypes are acquired by EMT-induced cancer cells. To address this point, we attempted to characterize EMT cells in more physiological, three-dimensional (3D) collagen gel culture. EMT was induced by treating three human carcinoma cell lines (A549, Panc-1 and MKN-1) with TGF-ß. The TGF-ß treatment stimulated these cells to overexpress the invasion markers laminin γ2 and MT1-MMP in 2D culture, in addition to the induction of well-known morphological change and EMT marker expression. EMT induction enhanced cell motility and adhesiveness to fibronectin and collagen in 2D culture. Although EMT cells showed comparable cell growth to control cells in 2D culture, their growth rates were extremely suppressed in soft agar and collagen gel cultures. Most characteristically, EMT-induced cancer cells commonly and markedly extended invasive protrusions in collagen gel. These protrusions were mainly supported by microtubules rather than actin cytoskeleton. Snail-introduced, stable EMT cells showed similar protrusions in 3D conditions without TGF-ß. Moreover, these protrusions were suppressed by colchicine or inhibitors of heat shock protein 90 (HSP-90) and protein phosphatase 2A. However, MMP inhibitors did not suppress the protrusion formation. These data suggest that EMT enhances tumor cell infiltration into interstitial stroma by extending microtubule-based protrusions and suppressing cell growth. The elevated cell adhesion to fibronectin and collagen and high cell motility also seem important for the tumor invasion.</p> </div

Effects of various inhibitors on protrusion formation of MKN-1 cells in 3D collagen gel.

<p>MKN-1 cells were incubated with 10 ng/ml TGF-ß in serum-containing medium in 3D collagen gel culture, as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0053209#pone-0053209-g005" target="_blank">Figures 5</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0053209#pone-0053209-g006" target="_blank">6</a>. To the collagen culture were added various inhibitors, and the protrusion formation was quantified 24 h later (A, C and D) or 3 h later (B). (A) The indicated concentrations of cytochalasin B and colchicine were added into the culture medium at the same time as the TGF-ß addition. (B) Cytochalasin B (5 µM) and colchicine (1 µM) were added into the culture medium after incubation with TGF-ß for 24 h. (C) MKN-1 cells were treated without (Control) or with cantharidin (1 µM) and/or radicicol (1 µM) as described in (A). (D) MKN-1 cells were pretreated with 10 µg/ml of each neutral antibody at 37°C for 30 min, and the pretreated cells were embedded into collagen gel containing 10 µg/ml of the indicated anti-integrin antibody and 10 ng/ml TGF-ß. All these inhibitors were not cytotoxic at least under the above experimental conditions, as analyzed by the trypan blue staining. However, cytotoxic effects became evident when the cells were incubated with 5 µM cytochalasin B or 1 µM colchicine for 24 h.</p

Cell adhesion activity of Lm332-ECM and purified Lm332 toward NHK cells.

<p>ECMs from ß3γ2-HEK and Lm332-HEK cultures and Lm332-coated plates were prepared as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035546#pone-0035546-g004" target="_blank">Figure 4</a>. (A) Phase-contrast microscopic images of NHK cells after 10 min incubation. Original magnification, ×300. Lm332 protein was coated at 1.0 µg/ml on the plate. (B) NHK cells suspended in KGM growth medium were inoculated into each well and then incubated at 37°C for 10 min. After the incubation, non-adherent cells were removed, and adherent cells were quantified. Numerical values under three right columns indicate the concentration at µg/ml of coated Lm332 protein. Each bar represents the mean ± S.D. of the fluorescent intensity (FI) for adherent cells in triplicate assays. The data shown are representative of at least three independent experiments performed.</p

A Metallacycle Fragmentation Strategy for Vinyl Transfer from Enol Carboxylates to Secondary Alcohol C–H Bonds via Osmium- or Ruthenium-Catalyzed Transfer Hydrogenation

A strategy for catalytic vinyl transfer from enol carboxylates to activated secondary alcohol C–H bonds is described. Using XPhos-modified ruthenium(0) or osmium(0) complexes, enol carboxylate–carbonyl oxidative coupling forms transient β-acyloxy-oxametallacycles, which eliminate carboxylate to deliver allylic ruthenium­(II) or osmium­(II) alkoxides. Reduction of the metal­(II) salt via hydrogen transfer from the secondary alcohol reactant releases the product of carbinol C–H vinylation and regenerates ketone and zero-valent catalyst

Fine structures of Lm332-ECM (left), ß3γ2-ECM (center) and purified Lm332 (right) were analyzed by TEM at a magnification of × 50,000.

<p>Bars indicate 100 nm.</p

Effect of sodium selenate on Lm332 deposition by NHK cells.

<p>(A) Immunoblotting analysis. NHK cells were inoculated in serum-free medium at a density of 4×10⁵ cells per 35-mm dish, incubated overnight, and treated with (+) or without (−) 0.1 mM sodium selenate (Sigma) at 37°C for 24 h. After the incubation, the ECM and CM were prepared from each culture and analyzed for the laminin α3 chain by immunoblotting as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035546#pone-0035546-g001" target="_blank">Figure 1</a>. (B) The ECMs from the control (none) and selenate-treated cultures (+selenate) were subjected to immunofluorescence staining with the anti-laminin α3 chain antibody BG5. (C) Phase-contrast micrographs of control and selenate-treated cultures. Other experimental conditions are described in “<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035546#s4" target="_blank">Materials and Methods</a>”.</p