Photobinding of carprofen to protein

Carprofen is a non-steroidal antiinflammatory drug with marked photosensitising properties. In order to elucidate the mechanisms underlying the phenomenon of drug-protein photobinding, mixtures of the drug and human serum albumin were irradiated under different experimental conditions. After irradiation and subsequent gel-filtration chromatography of the photomixture, the eluting protein fraction was analysed by means of fluorescence spectroscopy. The formation of drug-protein photoadducts could be evidenced by the characteristic emission properties of the carbazole chromophore. The photobinding of the drug to human serum albumin appears to involve the formation of aryl radicals resulting from carbon-halogen photocleavage. This mechanistic interpretation is supported by the observed variations in the intensity of the fluorescence spectra, which can be correlated with the lower quantum yield emission of chlorocarbazoles as compared to non-halogenated analogues. The results from laser flash photolysis studies are also in agreement with this proposal.     

7‐{Di­phenyl­[(tri­phenyl­phos­phine)­aurio]­phos­phine(1+)‐P}‐8‐methyl‐7,8‐dicarba‐nido‐undecaborate(1–) dichloro­methane hemi­solvate

The title compound, 7‐[(Ph₂P)Au(PPh₃)]‐8‐(CH₃)‐7,8‐nido‐C₂B₉H₁₀]·­0.5CH₂Cl₂ or [Au(C₁₅H₂₃B₉P)­(C₁₈H₁₅P)]·­0.5CH₂Cl₂, is the first reported gold derivative of the ligand [7‐­(Ph₂P)‐8‐(CH₃)‐7,8‐nido‐C₂B₉H₁₀]^?. It has a mono­nuclear structure with the gold centre in an essentially linear coordination [P—Au—P 174.041 (15)°]. The open C₂B₃ face contains one H atom that is strongly bonded to the central B atom and semi‐bridging to a neighbouring B atom [B—H distances 1.070 (16) and 1.45 (3) Å].     

The Gould-Jacobs Reaction of5-Aminoquinoxaline

 Reaction of 5-aminoquinoxaline with alkoxymethylene derivatives affords the corresponding quinoxalinoaminoethylenes. These undergo a thermal cyclization to yield angularly annelated 10H-pyrido[2,3-f]quinoxalines. The structures of all products were deduced from their IR, UV, mass, ¹H, and ¹³C NMR spectra.     

Conductive polyethylene-carbon black composites by elongational-flow injection molding Part 3. Study of the structure and morphology

The morphology and structure of high molecular weight linear polyethylene (M _w 450000) filled with carbon black and processed using molds that introduce an elongational flow component during injection molding has been examined using electron microscopy and x-ray diffraction techniques. The study of fracture surfaces reveals the display of shish-kebabs oriented along the injection direction with segregated longitudinal channels of carbon black particles. Molecular and lamellar changes in orientation are, furthermore, studied across the thickness of the moldings. It is shown that addition of carbon black particles to injection-molded polyethylene induces significant changes in lamellar orientation. Thus, while lamellar overgrowth proceeds perpendicular to the fiber axes within carbon free channels, lamellae grow randomly within carbon-enriched regions where flow is less pronounced.     

DNase activity ofMicrococcal endonuclease insolubilized on corn cob

The endonuclease from S. aureus has been immobilized on ground maize cob, previously activated with tosyl chloride. Pretreatment of the support on acid before tosylation yielded the best insoluble enzyme derivatives. The catalytic activity has been evaluated as percent of total hydrolysis attained in a batch reactor using DNA as a model substrate. The derivatives prepared are very resistant to high temperatures under conditions of catalysis (24 h at 45 degrees C). For these long reaction times, the extent of hydrolysis in the presence of small amounts of organic solvent (dimethyl sulfoxide at 2 percent) is larger than in plain buffer (Tris). This type of derivative could be very useful for the removal of nucleic acids from single-cell protein concentrates.     

Selection of sampling adsorbents and optimisation and validation of a GC-MS/MS method for airborne pesticides

A methodology for the sampling and determination of airborne pesticides has been developed. The trapping efficiency of three adsorbents, namely XAD-2,XAD-4 and a sandwich sorbent (PUF-XAD2-PUF), was tested for 34 pesticides and the latter was selected because it presented the highest retention capacity without breakthrough. Pesticides were determined by gas chromatography coupled to an ion trap mass spectrometer in tandem. The method showed recoveries ranging from 70% to 120% with limits of quantification in the range of 16.1–322.6 pg m^?3 when 155 m³ were sampled. This analytical strategy was applied to 10 indoor air samples collected in dwellings from the Valencian Region. Six pesticides, namely diphenylamine, pyrimethanil, bifenthrin, lambda-cyhalothrin, permethrin and cypermethrin were detected in indoor samples with concentrations ranging from 1.46 to 22.02 ng m^?3.     

Solvent- and metal-free selective oxidation of thiols to disulfides using I2/DMSO catalytic system

We describe herein a simple, fast and inexpensive protocol for the oxidative coupling of thiols employing a stoichiometric amount of DMSO and iodine as the catalyst. Various aromatic disulfides were obtained in good to excellent yields in short reaction times at room temperature, while aliphatic disulfides were achieved in good yields when the reactions were conducted under microwave irradiation.     

Determination of ethyl formate in magnesium chloride used as Ziegler-Natta catalyst support by Fourier transform infrared attenuated total reflectance spectrometry

FT-IR Spectroscopy with total attenuated reflectance (ATR) was used for the quantitative determination of ethyl formate coordinated in inorganic matrices such as magnesium chloride. The spectra were recorded directly on solutions obtained by dissolving the inorganic Ziegler-Natta supports in water. The method proposed is sensitive and rapid and appears to be very reliable when compared with other methods, such as solvent extraction followed by gaschromatographic or thermogravimetric analysis.     

Platinum(II) dibromo,bis (3,5-diamino-1(2)-triazolium) dibromide: Synthesis,crystal and molecular structure,and infrared characterization

The title compound C₄H₁₂PtN₁₀Br₄ was prepared and characterized by means of X-ray, and IR measurements. The crystals are monoclinic, space groupP2₁/c, (C _2h ⁵ No. 14) witha=6.875(1),b=15.478(2),c=7.074(1)Å,=90.98(1) andZ=2. The structure was solved by the heavy-atom method, and least-squares refinement of structural parameters led to a conventionalR factor of 0.031 (R _w=0.030) for 733 independent reflections. The compound exhibits discrete monometallic units with the 1,2,4-triazolium ion acting as modentate ligand. The structure consists of centrosymmetric units in which the platinum atom is coordinated in perfectly planar geometry by two nitrogen and two bromine atoms. The NH and NH₂ group of the guanazolium unit are involved in intermolecular hydrogen bonds. Infrared bands are diagnostic of the coordination environments around the metal atoms.     

Synthesis and crystal structure of [{V3(μ-Cl)4(μ 3-Cl) (μ 3-OH)(thf)2(teeda)}2]·2(thf) (teeda = N,N,N′N′-tetraethylethane-1,2-diamine)

The title complex was prepared from the reaction of [V₂(-Cl)₃(thf)₃]₂[Zn₂Cl₆] with N,N,NN-tetraethylethane-1,2-diamine (teeda) in refluxing thf and its crystal structure exhibits two triangulo-[V₃(-Cl)₃(-Cl)( ₃-OH)(thf)₂(teeda)]⁺ cations bridged by two chlorides. The molecular structure (monoclinic, space group P2 ₁/n, Z = 2, a = 11.8005(7) Å, b = 18.7492(14) Å, c= 15.6253(9) Å, = 103.600(4) shows each vanadium site in a distorted octahedral geometry. V1 and V2 have two thf molecules bounded in cis configuration, and V3 completes the hexa-coordination with the diamine teeda. Main bond distances are 2.5149(12) Å for V(1)--Cl(1), 2.062(3) Å for V(1)- ₃-O(3), 2.5554(12) Å for V(1)- ₃-Cl(4), 2.140(3) Å for V(1)–O(1)(thf), 2.243(4) Å for V(3)–N(1)(teeda), and 3.0437(9) for V(1)···V(2).