Microspectroscopic Study of Liposome-to-cell Interaction Revealed by Förster Resonance Energy Transfer

We report the Förster resonance energy transfer (FRET)-labeling of liposomal vesicles as an effective approach to study in dynamics the interaction of liposomes with living cells of different types (rat hepatocytes, rat bone marrow, mouse fibroblast-like cells and human breast cancer cells) and cell organelles (hepatocyte nuclei). The in vitro experiments were performed using fluorescent microspectroscopic technique. Two fluorescent dyes (DiO as the energy donor and DiI as an acceptor) were preloaded in lipid bilayers of phosphatidylcholine liposomes that ensures the necessary distance between the dyes for effective FRET. The change in time of the donor and acceptor relative fluorescence intensities was used to visualize and trace the liposome-to-cell interaction. We show that FRET-labeling of liposome vesicles allows one to reveal the differences in efficiency and dynamics of these interactions, which are associated with composition, fluidity, and metabolic activity of cell plasma membranes.     

Reaction of Vinyl Selenides with Secondary Phosphines and Elemental Selenium: One‐Pot Selective Synthesis of a New Family of Diselenophosphinic Se‐Esters

Alkyl vinyl selenides react with diverse secondary phosphines and elemental selenium in a 1.1:1:2 molar ratio (120–124°C, 20–40 min, 1,4‐dioxane) to afford selectively earlier unknown diselenophosphinic Se‐esters, R₂P(Se)SeCH(Me)SeR´, in 82–99% yield. This three‐component atom‐economic reaction proceeds via intermediate formation of diselenophosphinic acid R₂P(Se)SeH (generated from secondary phosphine and selenium), which adds to the double bond of vinyl selenide in a Markovnikov manner to give the target products.     

Calorimetric study of the copolymers on basis perfluorinated germanium hydrides with different structures

The temperature dependences of heat capacity of copolymers on the basis of perfluorinated germanium hydrides have been measured using an adiabatic vacuum calorimeter over the temperature range from 6 K to the final temperature of their stability for the first time. Thus, the physical transformations were detected and their thermodynamic characteristics were estimated. The experimental results were used to calculate the standard thermodynamic functions, namely heat capacity, enthalpy, entropy and Gibbs function over the range from T → 0 to the final temperature stability of copolymers. The standard entropy of formation of the under study copolymers at T = 298.15 K was calculated. The obtained results were compared with corresponding data for hyperbranching perfluor polyphenylenegermaniums with other structures. Some conclusions about dependences of the thermodynamic polymers properties versus their structures were made.     

Synthesis of cyclic carbonates from epoxides or olefins and CO2 catalyzed by metal-organic frameworks and quaternary ammonium salts

Catalytic properties of the metal-organic framework Cr-MIL-101 in solvent-free cycloaddition of CO₂ to epoxides to produce cyclic carbonates using tetrabutylammonium bromide as co-catalyst have been explored under mild reaction conditions (8 bar CO₂, 25 ⁰C). Styrene and propylene carbonates were formed with high yields (95% and 82%, respectively). Catalytic performance of Cr-MIL-101 was compared with other MOFs: Fe-MIL-101, Zn-MOF-5 and HKUST-1. The catalytic properties of different quaternary ammonium bromides, Cr-MIL-101 as well as PW₁₂/Cr-MIL-101 composite material have been assessed in oxidative carboxylation of styrene in the presence of both tert-butyl hydroperoxide and H₂O₂ as oxidants at 8–100 bar CO₂ and 25–80 ⁰C with selectivity to styrene carbonate up to 44% at 57% substrate conversion.     

A dynamic covalent, luminescent metallopolymer that undergoes sol-to-gel transition on temperature rise

The condensation of linear diamine and dialdehyde subcomponents around copper(I) templates in the presence of bulky trioctylphosphine ancillary ligands gave a linear, conjugated polymeric material in DMSO solution. This polymer solution was observed to undergo sol-to-gel transition as the temperature was raised to 140 °C, in contrast with the behavior of most gel-forming polymers, which do so upon cooling. We attribute the sol-to-gel transition to the formation of Cu(I)N(4) cross-links as the equilibria 2[Cu(I)N(2)P(2)] ? [Cu(I)N(4)] + [CuP(n)](+) + (4 - n)P favor the right-hand side at higher temperatures. The material was also observed to exhibit thermochromism and photoluminescence, with the color and intensity of both absorption and emission exhibiting temperature dependence. This material thus responds predictably to combinations of stimuli (heat, light, mechanical shear) in an interconnected way, as is required to generate complex function.     

Anti‐Aromatic versus Induced Paratropicity: Synthesis and Interrogation of a Dihydro‐diazatrioxa[9]circulene with a Proton Placed Directly above the Central Ring

We present a high‐yielding intramolecular oxidative coupling within a diazadioxa[10]helicene to give a dihydro‐diazatrioxa[9]circulene. This is the first [n]circulene containing more than eight ortho‐annulated rings (n>8). The single‐crystal X‐ray structure reveals a tight columnar packing, with a proton from a pendant naphthalene moiety centred directly above the central nine‐membered ring. This distinct environment induces a significant magnetic deshielding effect on that particular proton as determined by ¹H NMR spectroscopy. The origin of the deshielding effect was investigated computationally in terms of the NICS values. It is established that the deshielding effect originates from an induced paratropic ring current from the seven aromatic rings of the [9]circulene structure, and is not due to the nine‐membered ring being antiaromatic. UV/Vis spectroscopy reveals more efficient conjugation in the prepared diazatrioxa[9]circulene compared to the parent helical azaoxa[10]helicenes, and DFT calculations, including energy levels, confirm the experimental observations.     

Effect of the reaction parameters on the particle size in the dispersion polymerization of 2‐hydroxyethyl and glycidyl methacrylate in the presence of a ferrofluid

The precipitation of Fe₃O₄ from an aqueous solution with ammonium hydroxide produced nanoparticles that were coated with a layer of oleic acid [or, in some cases, poly(ethylene oxide) or poly(vinylpyrrolidone)] before their dispersion into the organic phase. The encapsulation of magnetite nanoparticles in poly(2‐hydroxyethyl methacrylate) or poly(2‐hydroxyethyl methacrylate‐co‐glycidyl methacrylate) microparticles was achieved by dispersion polymerization in toluene/2‐methylpropan‐1‐ol. Magnetic poly(glycidyl methacrylate) microparticles were obtained in the presence of poly(ethylene oxide) at the magnetite/monomer interface. The particles containing up to 20 wt % iron maintained their discrete nature and did not aggregate. The effect of the reaction medium polarity, the concentrations of the monomer, initiator, and stabilizer, and the temperature on the particle size, particle size distribution, and iron and oxirane group contents was studied. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1848–1863, 2003     

New α-substituted alkylbenzene- and dialkylbenzene-1,2-diphosphonates: side-chain metalation of tetraethyl 4-methyl- and 4,5-dimethylbenzene-1,2-diphosphonates

Carbocyclic 1,2-diphosphonates (1a, 1b) are prepared by the Diels-Alder reaction of classical donor alka-1,3-dienes (isoprene and 2,3-dimethyl-1,3-butadiene) with tetraethyl acetylene bisphosphonate. Their aromatization by the KMnO₄-Al₂O₃ system affords 4-methyl and 4,5-dimethylbenzene-1,2-diphosphonates (2a, 2b), used as precursor for the generation of benzyl-type carbanions (3a, 3b) by lithiation with lithium isopropylamide in THF at −80 °C. The carbanions react with electrophilic reagents (chlorotrimethylsilane, p-fluorobenzaldehyde, and ethyl trifluoroacetate) in situ to form corresponding α-substituted monoalkyl- and dialkylbenzenediphosphonates in good yields.     

Syntheses and Structures of the Germanides CaNiGe and MgCoGe as well as Chemical Bonding in CaNiGe and CaNi2Ge2

The intermetallic germanides CaNiGe and MgCoGe have been synthesized from the elements in sealed tantalum tubes in a high‐frequency furnace. The compounds were investigated by X‐ray diffractions both on powders and single crystals: CeFeSi structure type, P4/nmm, a = 4.19341(3), c = 6.6264(1) Å, wR2 = 0.030, 124 F² values, 10 variable parameters for CaNiGe and a = 3.8960(4), b = 6.1929(11) Å, wR2 = 0.048, 104 F² values, 10 variable parameters for MgCoGe. In CaNiGe and MgCoGe the transition metal and germanium atoms build [TGe] layers (T = Ni, Co), which are separated by the calcium and magnesium atoms, respectively. The crystal structures of CaNiGe and MgCoGe as well as chemical bonding in CaNiGe and CaNi₂Ge₂ are discussed in terms of LMTO bond structure calculation and analysis using the Electron Localization Function (ELF). The Ge–Ge bond formation in polyanionic network of CaNi₂Ge₂ can formally be regarded as oxidative coupling product of layers of CaNiGe.