The amounts Fe, Ba, Sr, K, Ca and Ti in some lichens growing in Erzurum province (Turkey)

The amounts of Fe, Ba, Sr, K, Ca and Ti were determined qualitatively and quantitatively by using energy-dispersive X-ray fluorescence in eight lichen species, Pinus sylvestris, rock and soil in district of Erzurum province (Turkey). Lichen species were Cetraria pinastri (Scop.) Gray, Dermatocarpon miniatum (L.) W. Mann, Lecanora muralis (Schreb.) Rabenh., Pseudevernia furfuracea (L.) Zopf., Ramalina capitata (Ach.) Nyl., Rhizoplaca chrysoleuca (sm.) Zopf., Rhizoplaca melanophthalma (DC.) Leuckert & Poelt, and Xanthoparmelia somloensis (Gyeln.) Hale. The standard addition method was used for the determination of the concentration of Fe, Ba, Sr, K, Ca and Ti. The experimental setup consists of a Si(Li) detector with a resolution of at and annular ⁵⁵Fe and ²⁴¹Am radioactive sources. By the use of intersite, interelement and interspecies comparisons, it is concluded that some metals within the thalli of lichens in Erzurum province may reach high levels even when these plants are growing in rural and isolated sites.     

pH-labile sheddable block copolymers by RAFT polymerization: Synthesis and potential use as siRNA conjugates

Well-defined amphiphilic block copolymers composed of hydrophilic and hydrophobic blocks linked through an acid-labile acetal bond were synthesized directly by RAFT polymerization using a new poly(ethylene glycol) (PEG) macroRAFT agent modified with an acid-labile group at its R-terminal. The new macroRAFT agent was used for polymerization of poly(t-butyl methacrylate) (PtBMA) or poly(cholesterol-methacrylate) (PCMA) to synthesize well-defined block copolymers with a PEG block sheddable under acidic conditions. The chain extension polymerization kinetics showed known traits of RAFT polymerization. The molecular weight distributions of the copolymers prepared using the new macroRAFT agent remained below 1.2 during the polymerizations and the molecular weight of the copolymers was linearly proportional to monomer conversions. The acid-catalyzed hydrolysis behavior of the PEG-macroRAFT agent and the PEG-b-PtBMA (Mn = 13,600 by GPC, PDI = 1.10) was studied by GPC, ¹H NMR and UV–vis spectroscopy. The half-life of acid-hydrolysis was 70 min at pH 2.2 and 92 h at pH 4.0. The potential use of the pH-labile shedding behavior of the copolymers was demonstrated by conjugating a thiol-modified siRNA to ω-pyridyldisulfide modified PEG-b-PCMA. The resultant PEG-b-PCMA-b-siRNA triblock modular polymer released PCMA-b-siRNA segment in acidic and siRNA segment in reductive conditions, as confirmed by polyacrylamide gel electrophoresis.     

Synthesis,Characterization and Antimicrobial Activity of a New Aromatic Sulfonyl Hydrazone Derivative and Its Transition Metal Complexes

In this study, benzenesulfonicacid‐1‐methylhydrazide (bsmh) derivatives such as 2‐hydroxy‐1‐naphtaldehydebenzenesulfonylhydrazone (Hnafbsmh) and its Ni(II), Pd(II), Pt(II), Cu(II), Co(II) complexes were synthesized. The structures of these complexes were investigated using elemental analyses (FT‐IR, LC‐MS, UV‐VIS), magnetic susceptibility and conductivity measurement techniques. The complexes were found to have general compositions [ML₂]. All the synthesized complexes were evaluated in vitro as antimicrobial agents against representative strains of six gram‐positive and four gram‐negative bacteria and as an antifungal agent by disc diffusion methods. All the bacteria and fungi studied were screened against some commercial antibiotics to compare them with our chemical's zone diameters.     

Novel synthesis of α-nitroalkenes from nitroalkanes via halogenation of intermediate N,N-bis(silyloxy)enamines

An approach to conjugated nitroalkenes via oxidation of N,N-bis(silyloxy)enamines with bromine or iodine in the presence of tetra-n-butylammonium acetate is described. The acetate ion plays a key role by acting as a mild desilylating reagent. This new strategy allows the synthesis of α-nitroalkenes from the corresponding nitroalkanes.     

2-silyloxy-1,2-oxazines, a new type of acetals of conjugated nitroso alkenes

3-alkyl-substituted 1,2-oxazine N-oxides 2 can be selectively transformed into 2-silyloxy-1,2-oxazines 1 upon treatment with silylating reagents. In the solid state derivatives 1 adopt a chair conformation with the pyramidal nitrogen atom, whereas in solution they exist as an equilibrating mixture of two conformers (DeltaG++ 55-60 kJ/mol). A preliminary study of the reactivity of nitrosals 1 has shown that they react with O- and N-stabilized carbocations to yield 1,2-oxazine N-oxides with a functionalized alkyl substituent at the 3-position. Moreover, compounds 1 can rearrange into silyloxy-1,2-oxazines 5 and react with morpholine to produce 3-morpholinoalkyl-1,2-oxazines 7 existing in a tautameric equilibrium with open-chain oximes 6.     

Angular-dependent metal-enhanced fluorescence from silver colloid-deposited films: opportunity for angular-ratiometric surface assays

We describe an exciting opportunity for Metal-Enhanced Fluorescence (MEF)-based surface assays using an angular-ratiometric approach to the observed enhanced emission from fluorophores in close proximity to silver colloids deposited on glass substrates. This approach utilizes the radiationless energy transfer (coupling) between the excited states of the fluorophore and the induced surface plasmons of the silver colloids, and the subsequent angular-dependent fluorescence emission from the fluorophore-silver colloid system. Since MEF is related to surface plasmons' ability to scatter light, angular-dependent light scattering from three different silvered surfaces and glass substrates were investigated using two common excitation angles, 45 and 90 degrees . The scattered light from silvered surfaces with a high loading was observed at wider angles on both sides of the glass substrates, while forward scattering (from the back of the glass) was dominant for the silvered surfaces with low loading, as explained by both Mie and Rayleigh theories. When silver colloids were placed between the fluorophore and glass interface, the coupled fluorescence emission through the higher refractive index glass (and in air), increased in an angular-dependent fashion, following closely the angular-dependent light scattering pattern of the silver colloids themselves. Similar observations for fluorescence emission from fluorophores deposited onto glass surfaces alone were made, but at much narrower angles on both sides of the fluorophore-glass interface and were simply explained by Lambert's cosine law. As the loading of silver on glass was increased, the enhanced fluorescence emission was observed at wider angles (towards 0 and 180 degrees ) at both sides of the silvered surfaces. Glass surfaces without silver colloids were used as control samples to demonstrate the benefits of MEF for enhancing fluorescence signatures in an elegant, angular-dependent fashion. Finally, the utility of the angular-dependent MEF phenomenon for intensity-based angular-ratiometric surface assays is demonstrated.     

Proton-conducting properties of the membranes based on poly(vinyl phosphonic acid) grafted poly(glycidyl methacrylate)

Proton-conducting properties of the graft copolymer electrolytes were examined throughout this work. The homopolymers poly(glycidyl methacrylate), PGMA and poly(vinyl phosphonic acid), PVPA were synthesized by free-radical polymerizations of the monomers glycidyl methacrylate, GMA, and vinyl phosphonic acid, VPA, respectively. The graft copolymers were produced by grafting of PVPA onto PGMA via ring opening of ethylene oxide groups. To examine the influence of the concentration of VPA on the proton conductivity, several graft copolymers were produced at various stoichiometric ratios with respect to monomer repeat units. The materials were characterized by FT-IR and ¹H NMR spectroscopy and the thermal properties were studied by thermogravimetry (TG) and differential scanning calorimetry (DSC). The TGA results demonstrated that the samples are thermally stable up to at least 150 °C. The proton conductivities of humidified and dry samples were studied via impedance spectroscopy. In the anhydrous state, the proton conductivity of P(GMA)-graft-P(VPA)₁₀ was 5 × 10^? 5 S/cm at 150 °C. The proton conductivity of the same material increased with the humidity content and reached to 0.03 S/cm at 80 °C under 50% of RH, which approached to that of Nafion^® at the same humidification level.     

Summability on Mellin-type nonlinear integral operators

In this study, approximation properties of the Mellin-type nonlinear integral operators defined on multivariate functions are investigated. In order to get more general results than the classical aspects, we mainly use the summability methods defined by Bell. Considering the Haar measure with variation semi-norm in Tonelli's sense, we approach to the functions of bounded variation. Similar results are also obtained for uniformly continuous and bounded functions. Using suitable function classes we investigate the rate of convergence in the approximation. Finally, we give a non-trivial application verifying our approach.     

Design,stereoselective synthesis and computational calculations of novel hybrid compounds via Pauson-Khand reactions

A series of novel chiral hybrid compounds between benzofuran and bicyclic cyclopentenone and also benzothiophene and bicyclic cyclopentenone have been designed and synthesized. Chiral enynes derived from enantiomerically enriched homoallyl and homopropargyl alcohols were converted into bicyclic cyclopentenone structures by intramolecular Pauson-Khand reactions. This strategy provides a facile access to various bicyclic cyclopentenones substituted with benzofuran or benzothiophene ring systems in good yields. In addition to the experimental work, the ground state geometries of the hybrid compounds were optimized using Density Functional Theory applications at the B3LYP/6-31G(d,p) level in order to obtain information about the 3D geometries and electronic structure.