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      Molecularly imprinted sol-gel silica for solid phase extraction of phenobarbital

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          Abstract

          A molecularly imprinted organically modified silica was prepared through a simple sol-gel procedure, and evaluated as specific sorbent for solid-phase extraction (SPE) of phenobarbital from aqueous and forensic samples. The analytical properties of the molecularly imprinted silica (MIS, non-imprinted sílica) were initially evaluated and the MIS was found to be specific towards the target species: the imprinting factor IF, measured as the ratio between phenobarbital peak areas in the MIS and NIS chromatograms, was estimated as 58. This value is considerably higher than those usually found for conventional methacrylate-based molecularly imprinted sorbents and suggests that non-specific analyte/sorbent interactions are insignificant in the MIS. This material is applied to the isolation of phenobarbital from aqueous samples and plasma; detection limit of 10 and 62 µg mL-1 was achieved for the former samples, respectively.

          Translated abstract

          Sílica organicamente modificada e molecularmente impressa foi preparada através de um procedimento sol-gel simples, e avaliada como sorvente específico para extração em fase sólida (Solid Phase Extraction, SPE) de fenobarbital em amostras aquosas e forenses. As propriedades analíticas dessa sílica molecularmente impressa (MIS, molecularly imprinted silica) foram inicialmente avaliadas e o material determinado como específico para as espécies-alvo: o fator de impressão IF, medido como a razão entre o pico do fenobarbital em cromatogramas de MIS e NIS (sílica não-impressa) foi estimado como 58. Este valor é consideravelmente maior que aquele apresentado normalmente para sorventes de impressão convencional baseados em metacrilatos e sugere que interações não-específicas analito/sorvente são insignificantes no MIS. O material foi aplicado no isolamento de fenobarbital de amostras aquosas e plasma; limites de detecção de 10 e 62 µg mL-1, respectivamente, foram encontrados para essas amostras.

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          Characterization of the FKBP.rapamycin.FRB ternary complex.

          Rapamycin is an important immunosuppressant, a possible anticancer therapeutic, and a widely used research tool. Essential to its various functions is its ability to bind simultaneously to two different proteins, FKBP and mTOR. Despite its widespread use, a thorough analysis of the interactions between FKBP, rapamycin, and the rapamycin-binding domain of mTOR, FRB, is lacking. To probe the affinities involved in the formation of the FKBP.rapamycin.FRB complex, we used fluorescence polarization, surface plasmon resonance, and NMR spectroscopy. Analysis of the data shows that rapamycin binds to FRB with moderate affinity (K(d) = 26 +/- 0.8 microM). The FKBP12.rapamycin complex, however, binds to FRB 2000-fold more tightly (K(d) = 12 +/- 0.8 nM) than rapamycin alone. No interaction between FKBP and FRB was detected in the absence of rapamycin. These studies suggest that rapamycin's ability to bind to FRB, and by extension to mTOR, in the absence of FKBP is of little consequence under physiological conditions. Furthermore, protein-protein interactions at the FKBP12-FRB interface play a role in the stability of the ternary complex.
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            Spectators Control Selectivity in Surface Chemistry: Acrolein Partial Hydrogenation Over Pd

            We present a mechanistic study on selective hydrogenation of acrolein over model Pd surfaces—both single crystal Pd(111) and Pd nanoparticles supported on a model oxide support. We show for the first time that selective hydrogenation of the C=O bond in acrolein to form an unsaturated alcohol is possible over Pd(111) with nearly 100% selectivity. However, this process requires a very distinct modification of the Pd(111) surface with an overlayer of oxopropyl spectator species that are formed from acrolein during the initial stages of reaction and turn the metal surface selective toward propenol formation. By applying pulsed multimolecular beam experiments and in situ infrared reflection–absorption spectroscopy, we identified the chemical nature of the spectator and the reactive surface intermediate (propenoxy species) and experimentally followed the simultaneous evolution of the reactive intermediate on the surface and formation of the product in the gas phase.
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              Modern Practice of Liquid Chomatography

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                Author and article information

                Journal
                jbchs
                Journal of the Brazilian Chemical Society
                J. Braz. Chem. Soc.
                Sociedade Brasileira de Química (São Paulo, SP, Brazil )
                0103-5053
                1678-4790
                2008
                : 19
                : 6
                : 1136-1143
                Affiliations
                [01] Campinas SP orgnameUniversidade Estadual de Campinas orgdiv1Instituto de Química Brazil
                Article
                S0103-50532008000600013 S0103-5053(08)01900613
                10.1590/S0103-50532008000600013
                5e19dfcd-46a8-4818-84d4-c8a58ded3391

                This work is licensed under a Creative Commons Attribution 4.0 International License.

                History
                : 18 July 2008
                : 06 September 2007
                Page count
                Figures: 0, Tables: 0, Equations: 0, References: 40, Pages: 8
                Product

                SciELO Brazil

                Categories
                Articles

                SPE,phenobarbital,ormosils,sol-gel,molecularly imprinted silica

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