Biomimetic biosensor based on lipidic layers containing tyrosinase and lutetium bisphthalocyanine for the detection of antioxidants

This paper describes the preparation of a biomimetic Langmuir-Blodgett film of tyrosinase incorporated in a lipidic layer and the use of lutetium bisphthalocyanine as an electron mediator for the voltammetric detection of phenol derivatives, which include one monophenol (vanillic acid), two diphenols (catechol and caffeic acid) and two triphenols (gallic acid and pyrogallol). The first redox process of the voltammetric responses is associated with the reduction of the enzymatically formed o-quinone and is favoured by the lutetium bisphthalocyanine because significant signal amplification is observed, while the second is associated with the electrochemical oxidation of the antioxidant and occurs at lower potentials in the presence of an electron mediator. The biosensor shows low detection limit (1.98 × 10-6 - 27.49 × 10-6 M), good reproducibility, and high affinity to antioxidants (KM in the range of 62.31-144.87 μM).\ud The excellent functionality of the enzyme obtained using a biomimetic immobilisation method, the selectivity afforded by enzyme catalysis, the signal enhancement caused by the lutetium bisphthalocyanine mediator and the increased selectivity of the curves due to the occurrence of two redox processes make these sensors exceptionally suitable for the detection of phenolic compounds.MICINN (AGL2009-12660/ALI)FAPESPCNPqCAPE

Lavras do Sul: A New Equilibrated Ordinary L5 Chondrite from Rio Grande do Sul, Brazil

The new Brazilian chondrite, Lavras do Sul, was found in 1985 at Lavras do Sul, Rio Grande do Sul State-Brazil (33°30′48″S; 53°54′65″W). It consists of a single mass weighing about 1 kg, covered by a black fusion crust with grayish interior. Four polished thin sections were prepared from a slice weighing 67 g on deposit at the Museu Nacional/UFRJ. It consists mostly of chondrules and chondrule fragments dispersed in a recrystallized matrix. Most chondrules are poorly defined and range in size from 300 to 2,000 μm, although some of them show distinct outlines, particularly when viewed under cross-polarized transmitted and reflected light. The texture of chondrules varies from non-porphyritic (e.g., barred-olivine, radial-pyroxene) to porphyritic ones (e.g., granular olivine as well as olivine-pyroxene). The meteorite contains mainly olivine (Fa24.9), low-Ca pyroxene (Fs22.6) and metal phases, with minor amounts of plagioclase, chromite and magnetite. Mössbauer Spectroscopy studies indicate that the metal phase is kamacite, tetrataenite and antitaenite. Veins of secondary iddingsite crosscut the thin section and some ferromagnesian silicates. The chemical composition indicates that Lavras do Sul is a member of the low iron L chondrite group. The poorly delineated chondritic texture with few well-defined chondrules, the occurrence of rare clinopyroxene and plagioclase (and maskelynite) with apparent diameters ranging from 5 to 123 μm led us to classify Lavras do Sul as an equilibrated petrologic type 5. The shock features of some minerals suggest a shock stage S3, and the presence of a small amount of secondary minerals such as iddingsite and goethite, a degree of weathering W1. The meteorite name was approved by the Nomenclature Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99).Fil: Zucolotto, M. E.. Universidade Federal Do Rio de Janeiro. Museu Nacional; BrasilFil: Antonello, Loiva. Centro Brasileiro de Pesquisas Fisicas; BrasilFil: Varela, Maria Eugenia. Consejo Nacional de Investigaciones Cienti­ficas y Tecnicas. Centro Cientifico Tecnologico San Juan. Instituto de Ciencias Astronomicas de la Tierra y del Espacio; ArgentinaFil: Scorzelli, R. B.. Centro Brasileiro de Pesquisas Fisicas; BrasilFil: Ludka, Isabel P.. Universidade Federal Do Rio de Janeiro. Instituto de Geociências; BrasilFil: Munayco, P.. Centro Brasileiro de Pesquisas Fisicas; BrasilFil: Dos Santos, E.. Centro Brasileiro de Pesquisas Fisicas; Brasi

The Rio do Pires Chondrite: petrographic and mineral chemistry features

O meteorito Rio do Pires é um condrito tipo L6 achado antes de 1992 na Bahia, Brasil, em data desconhecida, tendo seu registro publicado noMeteoriticalBulletin em 1994, através de análise simplificada requerida para esse procedimento, apresentada por Adrian Brearley da Universidade do Novo México, E.U.A. Esse estudo objetiva ampliar os dados existentes sobre esse meteorito, através do detalhamento de suas características petrográficas, químicas e mineralógicas. Foram realizadas análises em três lâminas polido-delgadas e em uma amostra de mão, utilizando microscópio petrográfico e lupa petrográficaestereomicroscópica, microssonda eletrônica (EPMA) e microscopia eletrônica de varredura (MEV). A análise petrográfica permitiu constatar a existência de veios de choque resultantes de evento colisional do corpo parental que originou esse meteorito. Aproximadamente 93% dos minerais que compõem essa rocha são transparentes, predominando cristais de olivina, piroxênio e plagioclásio, nesta ordem. Os minerais opacos são representados por grãos de Fe-Ni metálicos, troilita, cromita e whitlockita (merrilita).A olivina épredominantemente magnesiana (Fa25). O piroxênio é a enstatita e o plagioclásio oligoclásio. A mineraloquímica observada é similar a do bem estudado meteorito Suizhou, umcondrito do tipo L6. A matriz demonstra sinais de alta recristalização e presença de maskelinita, um importante indicador de choque, sendo significativa para o entendimento da história evolucional do Rio do Pires.Os novos dadosindicam um grau de choque entre S4 e S5 para este meteorito, em vez do grau S6 proposto quando de seu registro no MeteoriticalBulletin.The Rio do Pires meteorite is a L6 chondrite found in Bahia, Brazil, at an unknown date. It was registered at the Meteoritical Bulletin in 1994, through a simplified analysis required for this procedure, presented by Adrian Brearley, University of New Mexico, USA. This paper aims to broaden the existing data on this meteorite through detailed petrographic, chemical and mineralogical analysis. Such analyses were performed on three polished thin sections and a hand sample, using a petrographic microscope and stereomicroscopic petrographic magnifying glass, electron microprobe (EPMA) and scanning electron microscope (MEV). The petrographic analysis shows the existence of shock veins caused by an impact event of the parent body that originated this meteorite. Approximately 93% of the minerals that compose this rock are transparent, predominating crystals of olivine, pyroxene and plagioclase, in this order. Opaque minerals are represented by Fe-Ni metal grains, troilite, chromite, and whitlockite (merrilite). Olivine is predominantly magnesian (Fa ~ 25%). The pyroxene is the enstatite and the plagioclase is oligoclase. The observed mineral chemistry is similar to that of the well-studied Suizhou meteorite, a chondrite type L6. The matrix shows signs of high re-crystallization and presence of maskelynite, an important indicator of shock, being significant for understanding the evolutionary history of Rio do Pires. The new data indicate a S4 to S5 shock grade for this meteorite, instead of the S6 grade proposed when it was submitted to the Meteoritical Bulletin

Varre-Sai: The Recent Brazilian Fall

Varre-Sai, the most recent Brazilian meteorite fall, on June 19th, 2010 at Varre-Sai, in Rio de Janeiro State, Brazil (20°51′41″S; 41°44′. 80″W). At least eight masses (total ~3.5 kg) were recovered. Most are totally covered by fusion crust. The exposed interior is of light-grey colour with a few dark shock veins. Five thin polished and etched sections were prepared from a slice weighing 35 g on deposit at the National Museum/UFRJ. It consists mostly of chondrules ranging in size from 0.35 to ~2.2 mm, and chondrule fragments enclosed in a crystalline matrix. The matrix consists of tiny isolated subhedral and anhedral crystals and opaque minerals that are intergrown with broken chondrules. The chondritic texture is poorly defined with chondrule textures that vary from non-porphyritic to porphyritic ones. The essential minerals are olivine (Fa25±0.2) and low-Ca pyroxene (Fa21.66±0.2Wo1.4). Accessory minerals are plagioclase, apatite, Fe-Ni metal phases, troilite, chromite and magnetite. Mössbauer spectroscopy analysis confirms that the mineral phases are olivine, pyroxene, troilite and kamacite/taenite. Chemical data indicate that Varre-Sai is a member of the low iron L chondrite group. The observed texture and mineral phases led us to classify Varre-Sai as an equilibrated petrologic type 5. The shock features of the minerals (undulatory extinction, planar structure and numerous cracks), as well as plagioclase partial or totally transformed to maskelynite, suggest a shock stage S4. Also, some post-impact metamorphic processes could be inferred from the meta-sulfide conjoint grains that show complex mixtures of kamacite-taenite-tetrataenite and troilite. The occurrence of veins crosscutting the studied sections indicates that Varre-Sai was affected by a late fracturing event. Sealing of these fractures must have been a fast process, as shown by troilite globule textures pointing towards rapid solidification. The meteorite name was approved by the Nomenclature Committee of the Meteoritical Society (Meteoritic Bulletin, no 99).Fil: Zucolotto, M. E.. Universidade Federal Do Rio de Janeiro. Museu Nacional; BrasilFil: Antonello, L. L.. Centro Brasileiro de Pesquisas Físicas; BrasilFil: Varela, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; ArgentinaFil: Scorzelli, R. B.. Centro Brasileiro de Pesquisas Físicas; BrasilFil: Munayco, P.. Centro Brasileiro de Pesquisas Físicas; BrasilFil: dos Santos, E.. Centro Brasileiro de Pesquisas Físicas; BrasilFil: Ludka, Isabel P.. Universidade Federal do Rio de Janeiro; Brasi