Preparation of photocrosslinked sol‐gel composites based on urethane‐acrylic matrix,silsesquioxane sequences,TiO2, and Ag/Au Nanoparticles for use in photocatalytic applications

An acid urethane oligodimethacrylate based on poly(ethylene glycol) was synthesized and used in the preparation of hybrid composites containing silsesquioxane sequences and titania domains formed through sol‐gel reactions along with silver/gold nanoparticles (Ag/Au NPs) in situ photogenerated during the UV‐curing process. The photopolymerization kinetics studied by Fourier transform infrared spectroscopy and photoDSC showed that the photoreactivity of the investigated formulations depends on the amount of titanium butoxide (5–20 wt %) added in the system subjected to UV irradiation. The introduction of 1 wt % AgNO₃/AuBr₃ in formulations slightly improved the degree of conversion but diminished the polymerization rates. The formation of hybrid materials comprising predominantly amorphous TiO₂/SiO₂ NPs, with or without Ag/Au NPs, was confirmed through specific analyses. The evaluation of photocatalytic activity demonstrated that the synthesized hybrid films are suitable for the complete removal of organic pollutants (phenolic compounds) from water under UV irradiation (200–350 min) at low intensity (found in the solar radiation). © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1189–1204     

Volatiles composition and antioxidant activity Inula oculus-christi L. from Serbia

Abstract

The chemical composition of the essential oil and the volatiles obtained by static headspace (HS) of Inula oculus-christi L. is presented. The GC-MS analysis of the hydrodistilled oil resulted in the identification of 90 components, representing 92.7% of the oil. The most abundant compounds were: caryophyllene oxide (9.8%), trans-longipinocarveol (9.2%), eucalyptol (7.3%) and intermedeol (6.2%). The major constituent of I. oculus-christi L. HS volatiles was eucalyptol (87.4%). The antioxidant activity was evaluated by four different methods: 2,2-diphenyl-1-picryl-hydrazylhydrate free radical assay (DPPH), 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) method, total reducing power (TRP), ferric reducing antioxidant power (FRAP), and cupric reducing antioxidant capacity (CUPRAC). Total phenolic content in (TPC) examined oil was 177.95?µg GAE/mg oil. Radical scavenging potential of the oil was promising RSC-DPPH was 57.4% and RSC-ABTS was 82.7%.

     

Chemical profile and biological activities of Peltigera horizontalis (Hudson) Baumg. thallus and apothecia extracts

Abstract

The aim of this study was to determine, for the first time, the chemical composition of Peltigera horizontalis thallus and apothecia extracts (ether, ethyl acetate, dichloromethane and acetone) by HPLC-UV and GC-MS, and evaluate activity of genotoxic, anticholinesterase, antioxidant and antibacterial potential of acetone extracts. Major constituents of thallus extracts were gyrophoric acid, and methyl gyrophorate while dominant component of apothecia extracts was tenuiorin. The predominant volatile compounds in extracts were methyl orsellinate, dodecyl acrylate, orcinol and orcinol monomethyl ether. The thallus acetone extract at concentration of 2.0 µg mL^?1 gave the greatest decrease in the micronuclei frequency (22.4%) of all tested extracts. Apothecia extract showed stronger antioxidant activity as compared to thallus extract. Tested extracts at concentration of 10?mg mL^?1 exhibited inhibitory effect (16.5% for thallus and 12.8% for apothecia) on pooled human serum cholinesterase. P. horizontalis acetone extracts had no activity against the tested five bacteria strains.     

Preparation of sol�Cgel hybrid materials from ��-methacryloxypropyltrimethoxysilane and tetramethyl orthosilicate: study of the hydrolysis and condensation reactions

Organic?Cinorganic hybrid materials suitable for the development of sol?Cgel coatings for metallic surfaces were prepared by hydrolysis and condensation of ??-methacryloxypropyltrimethoxysilane (MAPTMS) and tetramethyl orthosilicate (TMOS). The hydrolysis of MAPTMS/TMOS was carried out in an ethanol/water solution. The prehydrolysis stage of MAPTMS/TMOS system was monitored by Fourier transform infrared spectroscopy (FTIR) and liquid-state ²⁹Si and ¹³C nuclear magnetic resonance (²⁹Si and ¹³C NMR). FTIR analysis indicated that the hydrolysis of MAPTMS/TMOS was accomplished as far as the (SiOMe) band corresponding to unhydrolyzed silane disappeared. The concentration of the alkoxy groups and the extent of self-condensation of mono-, di-, and trisubstituted siloxanes (T species) in the sol were estimated by using liquid-state ²⁹Si NMR spectroscopy. The hydrolysis of the prepared sol was also evaluated by liquid-state ¹³C NMR spectroscopy. The results indicated that under the adopted synthesis strategy conditions, the hydrolysis process requires 4?h to be completed.     

Effects of Sodium Butyrate on Cell Death Induced by Photodynamic Therapy in U373-MG and D54-MG Astrocytoma Cell Lines

The damage induced by end products of photodynamic therapy (PDT) in astrocytoma tumors leads to cytotoxicity and cell death. Chromatin modifiers such as sodium butyrate (NaB) induce several genes involved in apoptosis, among others. The PDT improvement was evaluated by the measurement of its effectiveness in the treatment of U373-MG and D54-MG astrocytoma cell lines exposed to NaB. Cells exposed to 80 μg mL⁻¹ of δ-aminolevulinic acid (ALA) as precursor of endogenous photosensitizer (PS), protoporphyrin IX (PpIX), induced 16.67% and 28.9% of mortality in U373-MG and D54-MG, respectively. The mortality increased to 70.62% and 96.7%, respectively, when U373-MG and D54-MG cells were exposed for 24 h to 8 m m NaB prior to ALA-induction. In this condition, re-expression of some genes related to apoptosis in U373-MG, and differentiation in D54-MG were induced. PpIX accumulation was higher than ALA-induction and the acetylation of histone H4 induced by NaB was verified by immunocytochemistry in both cells. It can be concluded that modified chromatin and genes induced by NaB increment the cellular death induced by PDT in astrocytoma cells using PpIX as endogenous PS.     

Stereochemistry modulates the catalytic hydrogenolysis of nitrile-substituted cyclopropanes

The study of Raney-Ni catalyzed chemo- and regioselective hydrogenolysis of diastereomeric nitrile-substituted spirocyclopropyloxindoles is presented. The chemoselectivity outcome of the reaction is remarkably influenced by the relative stereochemistry of the nitrile-substituted spirocyclopropyloxindoles. Chemo- and high regioselective cyclopropane ring-opening occurs from the syn diastereomers to give the corresponding 3-propylacetamide derivatives. X-ray crystallographic studies together with DFT model chemistry calculations indicate that chemo- and regioselectivity are directly dependent on the bond length asymmetry of the cyclopropane ring.     

Synthesis of copolymer-stabilized silver nanoparticles for coating materials

Silver ions being less toxic than silver nanoparticles, a more safe material can be obtained to be used as antimicrobial coating. This can be achieved by using thiol chemistry and covalently attach the silver nanoparticles in the coating. Our aim is to produce a coating having antimicrobial properties of silver ions but with the silver nanoparticles firmly attached in the coating. Here, we present a way to produce silver nanoparticles that can be used as a component in a coating or as such to produce an antimicrobial coating. The silver nanoparticles presented here are stabilized by a copolymer (poly(butyl acrylate–methyl methacrylate)) that is soft and has well-known good film-producing properties. The reversible addition-fragmentation chain transfer radical polymerization technique used to prepare the polymers provides conveniently a thiol group for effective binding of the silver nanoparticles to the polymers and thus to the coating.     

Synthesis,Characterization and X-Ray Crystal Structure of the Tri Aqua (3-Hydroxy-5-Hydroxymethyl-2-Methylpyridine-4-Carboxaldehyde-3-Methylisotiosemicarbazone: k<Superscript>3</Superscript>, O<Superscript>3</Superscript>, N<Superscript>7</Superscript>, N<Superscript>10</Superscript>) Ni(II) Nitrate

Abstract  

The title complex triaqua (3-hydroxy-5-hydroxymethyl-2-methylpyridine-4-carboxaldehyde-3-methylisothiosemicarbazone-k³,O³,N⁷,N¹⁰)Ni(II) nitrate ([Ni(PLITSC)(H₂O)₃](NO₃)₂, 1) represents the second transition metal complex incorporating an isothiosemicarbazide-pyridoxal based Schiff base that has been crystallographically characterized. Complex 1 crystallizes in a P21/n space group, with lattice constants: a = 11.2254(1) ?, b = 12.9941(2) ?, c = 12.8663(2), β = 96,7713(5)°, V = 1863.64(4) ?³, Z = 4, F(000) = 1016, R ₁ = 0.0681, wR ₂ = 0.1201. The central Ni(II) cation is found in a six-coordinate octahedral geometry formed by the tridentate Schiff base ligand PLITSC and three water molecules. The identity of 1 was further confirmed by elemental analysis, IR spectra, and conductometric and magnetochemical measurements.     

(3, 3)-Ary Differential Rings

The main purpose of this paper is to introduce the concept of (3, 3)-ary differential rings as a generalization of differential rings. Then we study ideals, prime ideals, radical and nil ideals of them. Finally, we give a construction of hyperstructures determined by (3, 3)-ary differential rings.     

Hydrolysis of phosphotriesters: a theoretical analysis of the enzymatic and solution mechanisms

A theoretical study on the alkaline hydrolysis of paraoxon, one of the most popular organophosphorus pesticides, in aqueous solution and in the active site of Pseudomonas diminuta phosphotriesterase (PTE) is presented. Simulations by means of hybrid quantum mechanics/molecular mechanics (QM/MM) potentials show that the hydrolysis of paraoxon takes place through an A(N)D(N) or associative mechanism both in solution and in the active site of PTE. The results correctly reproduce the magnitude of the activation free energies and can be used to rationalize the observed kinetic isotope effects (KIEs) for the hydrolysis of paraoxon in both media. Enzymatic hydrolysis of O,O-diethyl p-chlorophenyl phosphate, a phosphotriester having a leaving group with higher pK(a) than paraoxon, was also simulated. Hydrolysis of this phosphotriester by PTE follows a A(N)+D(N) mechanism with a pentacoordinate intermediate. Moreover, the leaving group of this new substrate coordinates to one of the zinc ions of the bimetallic active site in order to stabilize the large negative charge developed on the oxygen atom of the leaving group when the P-O bond is broken in the products state. To accommodate this new ligand in the coordination shell, carbamylated Lys169 must be displaced from one zinc ion to the other, which in turn affects the acidity of Asp301, a residue originally bound to the second zinc ion. This ability to displace some of the ligands of the coordination shell of the zinc centers would explain the promiscuity of this enzyme, which is capable of catalyzing hydrolysis of different substrate by means of different mechanisms.