Rh(III)-Catalyzed One-Step Synthesis of ortho-Alkynylated Perylene Imide Dyes: Optical and Electrochemical Properties of New Derivatives

A one-step Rh-catalyzed site-selective ortho-C−H alkynylation of perylene as well as naphthalene mono- and diimides is reported. A single step regioselective access to ortho-C−H alkynylated derivatives of these ryleneimides not only increases the step economy of the ortho-functionalization on these dyes but also provides a quick access route towards highly functionalized dyes that have potential optoelectronic applications. Increased solubility of tetra(triisopropylsilyl)acetylenyl PDIs in organic solvents greatly enhances their utility for further derivatization.     

Synthesis of Small‐Sized,Porous, and Low‐Toxic Magnetite Nanoparticles by Thin POSS Silica Coating

In this communication, we report the synthesis of small‐sized (<10 nm), water‐soluble, magnetic nanoparticles (MNPs) coated with polyhedral oligomeric silsesquioxanes (POSS), which contain either polyethylene glycol (PEG) or octa(tetramethylammonium) (OctaTMA) as functional groups. The POSS‐coated MNPs exhibit superparamagnetic behavior with saturation magnetic moments (51–53 emu g^?1) comparable to silica‐coated MNPs. They also provide good colloidal stability at different pH and salt concentrations, and low cytotoxicity to MCF‐7 human breast epithelial cells. The relaxivity data and magnetic resonance (MR) phantom images demonstrate the potential application of these MNPs in bioimaging.     

Design and development of a common synthetic strategy for a variety of 1-N-iminosugars

[formula: see text] A new synthetic strategy has been developed for a general approach toward the synthesis of a variety of 1-N-iminosugar-type glycosidase inhibitors utilizing precursors developed by the PET-mediated cyclization of alpha-trimethylsilylmethylamine radical cation to a tethered pi-functionality.     

Radiation synthesis of superabsorbent poly(acrylic acid)–carrageenan hydrogels

A series of superabsorbent hydrogels were prepared from carrageenan and partially neutralized acrylic acid by gamma irradiation at room temperature. The gel fraction, swelling kinetics and the equilibrium degree of swelling (EDS) of the hydrogels were studied. It was found that the incorporation of even 1% carrageenan (sodium salt) increases the EDS of the hydrogels from 320 to 800 g/g. Thermal analysis were carried out to determine the amount of free water and bound water in the hydrogels. Under optimum conditions, poly(acrylic acid)–carrageenan hydrogels with high gel fraction (80%) and very high EDS (800 g/g) were prepared gamma radiolytically from aqueous solution containing 15% partially neutralized acrylic acid and 1–5% carrageenan. The hydrogels were also found to be sensitive to the pH and the ionic strength of the medium.     

A new access to polyhydroxy piperidines of the azasugar class: synthesis and glycosidase inhibition studies

A new synthetic strategy has been devised to access a variety of polyhydroxylated piperidines belonging to the azasugar class of glycosidase inhibitors. The key precursor (3aR, 7aR)-5-benzyl-2,2-dimethyl-7-methylenehexahydro[1,3]dioxo[4,5-c]pyridine is obtained by photoinduced electron transfer (PET) cyclization of the corresponding alpha-trimethylsilylmethylamine radical cation to the tethered acetylene functionality. The new molecules have been evaluated for inhibitory properties for certain beta-glycosidases and have been found to be moderate to weak inhibitors of the enzymes under study.     

Nucleophilic dephosphorylation of p-nitrophenyl diphenyl phosphate in cationic micellar media

The kinetics of nucleophilic dephosphorylation of p-nitrophenyl diphenyl phosphate by hydroxamate ions (R'(C=O)N(RO-)) have been investigated in aqueous cationic micellar media at pH 9.12 and 27 degrees C. The pseudo-first-order rate constant-surfactant profiles show micelle-assisted bimolecular reactions involving interfacial ion exchange between bulk aqueous media and micellar pseudophase. N-Substituted hydroxamate ion shows higher reactivity over the unsubstituted hydroxamate ions in cationic micellar media. The kinetic data are discussed in terms of the pseudophase ion exchange model.     

Product Control using Substrate Design: Ruthenium‐Catalysed Oxidative C−H Olefinations of Cyclic Weinreb Amides

A new class of Weinreb amides has been developed as directing groups for the ruthenium‐catalysed regioselective oxidative C?H olefination. The new Weinreb amides successfully inhibit the N?O bond reductive cleavage usually associated with the cationic ruthenium system, thereby keeping intact the synthetic utility of Weinreb amides. Mechanistic studies reveal interesting aspects of the directing group capabilities of Weinreb amides when compared to simple amides of similar structures.     

Almost global attitude consensus of multi-agent rigid bodies on $$\mathrm{TSO}(3)^N$$ TSO ( 3 ) N in the presence of disturbances and directed topology

Nonlinear Dynamics - The article proposes a distributed attitude consensus algorithm for multi-agent rigid bodies on the tangent bundle $$\mathrm{TSO}(3)^N$$ . It is assumed that a directed fixed...     

Hydrolytic Cleavage of Paraoxon by Octanohydroxamate Ion in Cationic Microemulsions

The hydrolysis reaction of O,O‐diethyl O‐p‐nitrophenylphosphate (Paraoxon) with the octanohydroxamate ion (OHA^?) was studied in a cationic oil‐in‐water (O/W) microemulsion system over a pH range 7.5–12.0 at 300 K. The O/W systems are stabilized by using cationic surfactant, cetyltrimethylammonium bromide (CTAB), and n‐butanol as cosurfactants. In a microemulsion, the rate enhancement by OHA^? is greater toward the cleavage of paraoxon than its spontaneous (2.1 × 10⁷ s^?1) hydrolysis. The k_obs values for the reaction of paraoxon with OHA^? were determined in different microemulsion compositions with varying chain length of alcohols (n‐butanol, n‐pentanol, n‐octanol, and n‐dodecanol) and alkanes (n‐hexane, n‐heptane, and n‐decane). The effects of water content, pH, and size of the oil pool have been discussed.     

A two-step stimulus-response cell-SELEX method to generate a DNA aptamer to recognize inflamed human aortic endothelial cells as a potential in vivo molecular probe for atherosclerosis plaque detection

Aptamers are single-stranded oligonucleotides that are capable of binding wide classes of targets with high affinity and specificity. Their unique three-dimensional structures present numerous possibilities for recognizing virtually any class of target molecules, making them a promising alternative to antibodies used as molecular probes in biomedical analysis and clinical diagnosis. In recent years, cell-systematic evolution of ligands by exponential enrichment (SELEX) has been used extensively to select aptamers for various cell targets. However, aptamers that have evolved from cell-SELEX to distinguish the “stimulus-response cell” have not previously been reported. Moreover, a number of cumbersome and time-consuming steps involved in conventional cell-SELEX reduce the efficiency and efficacy of the aptamer selection. Here, we report a “two-step” methodology of cell-SELEX that successfully selected DNA aptamers specifically against “inflamed” endothelial cells. This has been termed as stimulus-response cell-SELEX (SRC-SELEX). The SRC-SELEX enables the selection of aptamers to distinguish the cells activated by stimulus of healthy cells or cells isolated from diseased tissue. We report a promising aptamer, N55, selected by SRC-SELEX, which can bind specifically to inflamed endothelial cells both in cell culture and atherosclerotic plaque tissue. This aptamer probe was demonstrated as a potential molecular probe for magnetic resonance imaging to target inflamed endothelial cells and atherosclerotic plaque detection.