Formation of antifouling functional coating from deposition of a zwitterionic-co-nonionic polymer via “grafting to” approach

We develop a new process for the preparation of synergistic antifouling functional coatings on gold surfaces via a “grafting to” approach. The strategy includes a synthetic step of polymer brushes that consist of poly (ethylene glycol) (PEG) and zwitterionic side chains via a typical reversible-addition fragmentation chain transfer (RAFT) polymerization process, and a subsequent deposition of the polymer brushes onto a gold substrate. The presence of PEG and zwitterion chains on these polymer brush-coated gold surfaces has been proved to have a synergistic effect on the final antifouling property of the coating. PEG chains lower the electrostatic repulsion between zwitterionic polymer chains and increase their graft density on gold surfaces, while zwitterionic polymer effectively improves the antifouling property that is offered by PEG chains alone. Protein adsorption and cell attachment assays tests are conducted to confirm that this copolymer layer on gold surface has a pronounced resistance against proteins such as Bovine serum albumin and Lysozyme. Importantly, the antifouling property can be systematically adjusted by varying the molar ratio of PEG to zwitterionic chains in the final coating copolymer.     

EPR studies of “self-spin-probing” reactions between the carbanion of nitroalkanes and ω-hydroperfluorodiacyl peroxides

The mechanism of “self-spin-probing” reactions between carbanion of nitroalkanes (1) and ω-hydroperfluorodiacyl peroxides (2) initiated by electron transfer has been verified by EPR detection of new bis(ω-hydroperfluoro-dialkyl) nitroxides (11) and ω-hydroperfluoroalkyl nitroalkyl nitroxides (12) — spin adducts of radical intermediates H(CF₂CF₂)_n · (n=1,2,3) and R¹R²C·NO₂ to the nitroso trap H(CFCF)_nNO (9) generated in the reactions.     

Mechanism of the reaction of 1,1′-diethylferrocene and decamethylferrocene with peroxides in organic solvents

Kinetic relationships of oxidation of 1,1′-diethylferrocene and decamethylferrocene with peroxides ROOR (R = H, t-C₄H₉) in organic solvents were studied and the composition of oxidation products was established. It is shown that reactivity of (C₅H₄C₂H₅)₂Fe is significantly lower than that of Cp*₂Fe [Cp* = η⁵-C₅(CH₃)₅] which is seen from the ability of the first metal complex to undergo oxidation with a notable rate only in the presence of Brønsted acids, whereas the second substance is oxidized both in the presence and in the absence of these acids. Two possible mechanisms of oxidation of metal complexes in the presence of strong acids are discussed. One of them is based on the ability of ferrocene to fast and equilibrium protonation with the formation of Cp₂Fe⁺—H structure. Another one considers the ability of metal complexes to coordinate peroxides with the formation of weakly bound charge transfer complexes of the composition Cp₂Fe^δ+·ROOR^δ-. The possibility of their formation is confirmed by the oxidation of Cp₂Fe with hydroperoxides in the absence of acids.     

In vivo and in vitro emergence of simultaneous resistance to both β-lactam and aminoglycoside antibiotics in a strain of Serratia marcescens

In a patient with Serratia marcescens bacteraemia, a variant resistant to cefotaxime and amikacin was isolated in a blood culture under combined treatment with cefotaxime and amikacin. In addition, in vitro selection on cefotaxime and/or amikacin yielded resistant mutants from the sensitive parent strain. These mutants displayed the same type of cross-resistance as the clinical strain to all β-lactam and aminoglycoside antibiotics. The mechanisms for this resistance was a decrease in the permeability of the cell. To our knowledge, the isolation of such strains from blood cultures and the mechanism responsible for this ⪡ broad-spectrum resistance ⪢ have not been previously described.     

Supramolecular assembly of Keggin polyoxomolybdate and 2,2’-bipyridine generated in situ from a decarboxylation coupling reaction

An assembly of Keggin polyoxomolybdate and organic substrate（Hbipy）₃[PMo₁₂O₄₀]（1,bipy=2,2’-bipyridine） was synthesized and characterized by elemental analysis,infrared spectrum,and single-crystal X-ray analysis.The ligand bipy of compound 1 was generated by a decarboxylation coupling reaction of H₂pdc（H₂pdc=pyridine-2,6-dicarboxylic acid） in situ under hydrothermal reaction conditions and the control experiments illustrate that La（NO₃）₃ or Ce（NO₃）₃,which does not appear in the final structure,is necessary for the decarboxylation coupling reaction.Moreover,compound 1 displays strong photoluminescence property in the solid state at room temperature.     

Development,relevance, and applications of “atom-at-a-time” techniques

A brief history of the development and some of the first uses of “atom-at-a-time” techniques to investigate the chemical and nuclear properties of the actinide and transactinide elements are presented. The currently known transactinides (all elements with Z > 103) were discovered using physical (nuclear) techniques rather than chemical separation techniques because of their short half-lives and low production rates and the difficulty in accurately predicting chemical properties of the heaviest elements because of relativistic effects. Some of the constraints on systems suitable for such studies and whether these tracer-scale results can be extended to the macro-scale are discussed. The relevance and importance of the methods and their potential for application to some current problems such as nuclear forensics and proliferation and environmental concerns are considered. The value of graduate research utilizing such techniques in helping to attract and educate the next generation of nuclear scientists is highlighted.     

A novel approach to the synthesis of optically pure non protein α-amino acids in both L and D configurations from L-serine

Efficient syntheses of (2R)-2-Boc-amino-3-phenylsulfonyl-l-propanol 3 and its enantiomer 9 from L-serine are described. The potential of these compounds in a novel general method for the synthesis of optically pure non protein α-amino acids in both the L and D configurations is exemplified by the preparation of N-Boc-L-and D-homophenylalanine, -norvaline and -norleucine.     

The chemistry of photolytically and thermally generated α-ketocarbenes from iodonium ylides of β-diketones

The reactions of Phenyliodonium dimedonate,1,with various double bonds were investigated. The products are always heterocyclic copmounds(5-member ring) in good yield.     

Enantioselective zinc/BINOL-catalysed alkynylation of aldimines generated in situ from α-amido sulfones

Chiral nonracemic N-Cbz-protected propargylic amines have been prepared by the addition of terminal alkynes to imines generated in situ from α-amido sulfones in the presence of diethylzinc and BINOL-type ligands as catalysts. The reactions give good yields and high enantioselectivities (ee values up to 95?%) for a good number of aromatic and heteroaromatic α-amido sulfones and alkynes.     

The role of water release from the cyclodextrin cavity in the complexation of benzoyl chlorides by dimethyl-β-cyclodextrin

The influence of temperature on the solvolysis of substituted benzoyl chlorides in the presence of dimethyl-β-cyclodextrin (DM-β-CD) was studied. Based on the influence of the DM-β-CD concentration on chemical reactivity in this process, the cyclodextrin has a catalytic effect on the solvolysis of 4-nitrobenzoyl chloride (4-NO₂) but an inhibitory effect on that of 4-methoxy-(4-MeO), 3-chloro-(3-Cl) and 3-trifluoromethyl-(3-CF₃) benzoyl chlorides. These disparate effects are related to a difference in reaction mechanism; thus, DM-β-CD catalyses associative solvolysis and inhibits dissociative solvolysis. Examining the influence of temperature on the solvolytic process allowed the stoichiometry of the host-guest complexes formed to be established. The formation constants for the complexes of meta-substituted benzoyl chlorides increased with increasing temperature. On the other hand, the equilibrium formation constants for the 1:1 host-guest complexes of para-substituted benzoyl chlorides exhibited the opposite trend. The equilibrium formation constant for 2:1 host-guest complexes for the para-substituted benzoyl chlorides increased with increasing temperature. These differences are ascribed to the release of water from the DM-β-CD cavity during the formation of the host-guest complex.     

Studies on the active species in olefin polymerisation generated from phenoxo-amido titanium “chiral-at-metal” compounds

Treatment of RHN-CH₂-(3,5-tBu₂C₆H₂-2-OH) (R = C₆H₅ 1a, p-MeC₆H₄ 1b, Cy 1c; Cy = cyclohexyl) with 1 equiv of TiCp1Cl₃ (Cp1 = η⁵-C₅Me₅) in the presence of 2.5 equiv of NEt₃ in pentane or hexane at room temperature gives the monocyclopentadienyl phenoxo-amido monochloro complexes [TiCp1{RN-CH₂-(3,5-tBu₂C₆H₂-2-O)}Cl] (R = C₆H₅ 2, p-MeC₆H₄ 4, Cy 5). In a more polar solvent the phenoxo-amino complex [TiCp1{(C₆H₅)(H)N–CH₂-(3,5-tBu₂C₆H₂-2-O)}Cl₂] (3) is obtained from the reaction with 1a. The reaction of TiCp1Cl₃ with tBu(H)N–CH₂-(3,5-tBu₂C₆H₂-2-OH) (1d) affords the complex [TiCp1{tBu(H)N–CH₂-(3,5-tBu₂C₆H₂-2-O)}Cl₂] (6) in which no coordination of the amino group to the metal centre is observed as a consequence of the high steric requirements of the amino substituent in the phenol-amine. All the reported compounds were characterised by the usual analytical and spectroscopic methods and the molecular structures of 2 and 5 were determined by X-ray diffraction analysis from suitable single crystals.Studies of catalytic activity for ethylene or propylene polymerisation using boron or aluminium reagents as cocatalysts were performed under different conditions. In general the trends observed for the phenoxo-amido precatalysts with the aluminium reagent as cocatalyst in the α-olefin polymerisation reactions might suggest a catalyst decomposition process through ligand abstraction by sMAO. The activity found for ethylene or propylene polymerisation when B(C₆F₅)₃ or [CPh₃][B(C₆F₅)₄] are used as cocatalysts is related to the strength of the cation-anion interactions.     

Production of Acid-Stable and High-Maltose-Forming α-Amylase of Bacillus acidicola by Solid-State Fermentation and Immobilized Cells and Its Applicability in Baking

Among matrices used for immobilizing Bacillus acidicola cells [calcium alginate, chitosan + alginate, scotch brite, and polyurethane foam (PUF)], ??-amylase production was highest by PUF-immobilized cells (9.1?U?ml^?1), which is higher than free cells (7.2?U?ml^?1). The PUF-immobilized cells could be reused over seven cycles with sustained ??-amylase production. When three variables (moisture, starch, and ammonium sulfate), which significantly affected enzyme production in solid-state fermentation (SSF), were optimized using response surface methodology, 5.6-fold enhancement in enzyme production was attained. The enzyme production in SSF is 3.8-fold higher than that in submerged fermentation. The bread made by supplementing dough with ??-amylase of B. acidicola scored better than those with the xylanase of Bacillus halodurans and thermostable ??-amylase of Geobacillus thermoleovorans.     

Asymmetric epoxidation of olefins by chiral dioxiranes generated in situ from ketones of d-(−)-quinic acid

The in situ generated dioxiranes (Caroate as peroxide source) of the optically active ketones 4a and 4b, which may be conveniently prepared from d-(−)-quinic acid, serve as effective oxidants for the asymmetric epoxidation (ee values up to ca. 90% with 4a) of prochiral olefins.     

Does the decomposition of peroxydicarbonates and diacyl peroxides proceed in a stepwise or concerted pathway?

M?ller-Plesset perturbation theory and density functional theory calculations are used to study decomposition mechanisms of polymerization initiators, such as diethyl peroxydicarbonate, trifluoroacetyl peroxide, and acetyl peroxide, which possess a general structure of RC(O)OO(O)CR. It is found that the decomposition of initiators with electron-donating R groups follows two favorable stepwise pathways: a two-bond cleavage mechanism in which the O-O single bond and one of R-C bonds of [R-C(O)O-O(O)C-R] break simultaneously followed by decomposition of the R-C(O)O(*) radical and a one-bond cleavage mechanism in which the single O-O bond cleavage produces a carboxyl radical pair and a subsequent decomposition of the carboxyl radicals. It is also found that the initiators with electron-withdrawing R groups follow the two-bond cleavage pathway only. Geometrical and energetic analyses indicate that despite the similar structures of the peroxydicarbonates, quite different decomposition energy barriers are determined by the nature of the R groups.     

Selective synthesis of cyclic triperoxides from 1,1′-dihydroperoxydi(cycloalkyl)peroxides and acetals using SnCl4

Russian Chemical Bulletin - A method for the synthesis of 1,2,4,5,7,8-hexaoxonanes by the reaction of 1,1′-dihydroperoxydi(cycloalkyl)peroxides with acetals using SnCl4 has been developed....     

Scope and Applicability of an Expedient Synthesis Leading to Polysubstituted 3‐(Carboxyphenyl)pyrroles

A convenient three‐step route toward a functionalized pyrrole building block for novel anti‐inflammatory agents is reported. In contrast to previous strategies, the present approach focuses on inexpensive starting materials and application on a multigram scale. A high degree of functional diversity is demonstrated in various derivatives, and the scope and limitations of this route are discussed. Complementary to the described tetrasubstituted pyrroles, a novel ring‐closure protocol based on the Feist–Benary condensation affords trisubstituted analogues.     

Double Michael–Pudovik addition of generated in situ silylic esters of trivalent phosphorus to unsaturated compounds

Russian Journal of General Chemistry -     

Thermodynamics of nucleic acid bases and nucleosides in water from 25 to 55°C

Specific heat capacities, apparent molar heat capacities, densities, and apparent molar volumes have been determined for cytosine, uracil, thymine, adenine, cytidine, 2-deoxycytidine, uridine, thymidine and adenosine at temperatures from 25°C to 55°C. The results of these measurements have been used to calculate for the first time, the thermodynamic quantities:C _p,2 ^o , (C _p,2 ^o /T)_p, (² C _p,2 ^o T ²)_p,V ₂ ^o , (V ₂ ^o /T)_p, and (² V ₂ ^o /T ²)_p. The-CH₂-group contribution has been calculated at different temperatures. It has also been observed from the data for the nucleic acid bases and nucleosides that the additivity ruleC _p,2 ^o (nucleoside)-C _p,2 ^o (base) +C _p,2 ^o (water)=C _p,2 ^o (ribose) does not hold in these cases.     

Photoaddition reactions of azomethine ylides generated from α-aminonitriles to fullerene C60: Formation of fulleropyrrolidines and reaction efficiencies changes depending on reaction conditions

Photoaddition reactions of C₆₀ with both (trimethylsilyl)methyl and either benzyl or phenethyl group containing α-aminonitriles were carried out to explore how product distributions and reaction efficiencies can be influenced by reaction solvent systems. The results show that photoreactions produce both trimethylsilyl- and cyano group containing fulleropyrrolidines as a major (or exclusive) product. Especially, photoreactions performed in either EtOH containing solution or oxygenated environment take place with a much more efficient manner.