An optimization model for metabolic pathways

This article is available open access through the publisher’s website through the link below. Copyright @ The Author 2009.Motivation: Different mathematical methods have emerged in the post-genomic era to determine metabolic pathways. These methods can be divided into stoichiometric methods and path finding methods. In this paper we detail a novel optimization model, based upon integer linear programming, to determine metabolic pathways. Our model links reaction stoichiometry with path finding in a single approach. We test the ability of our model to determine 40 annotated Escherichia coli metabolic pathways. We show that our model is able to determine 36 of these 40 pathways in a computationally effective manner. Contact: [email protected] Supplementary information: Supplementary data are available at Bioinformatics online (http://bioinformatics.oxfordjournals.org/cgi/content/full/btp441/DC1)

Enhancing Metalating Efficiency of the Sodium Amide NaTMP in Arene Borylation Applications

Though LiTMP (TMP=2,2',6,6'-tetramethylpiperidide) is a commonly used amide, surprisingly the heavier NaTMP has hardly been utilised. Here, by mixing NaTMP with tridentate donor PMDETA (N,N,N',N'',N''-pentamethyldiethylenetriamine), we provide structural, and mechanistic insights into the sodiation of non-activated arenes (e.g. anisole and benzene). While these reactions are low yielding, adding B(OiPr)3 has a profound effect, not only by intercepting the CAr -Na bond, but also by driving the metalation reaction towards quantitative formation of more stabilized sodium aryl boronates. Demonstrating its metalating power, regioselective C2-metalation/borylation of naphthalene has been accomplished contrasting with single-metal based protocols which are unselective and low yielding. Extension to other arenes allows for in situ generation of aryl boronates which can then directly engage in Suzuki-Miyaura couplings, furnishing a range of biaryls in a selective and efficient manner

Assessing Alkali-Metal Effects in the Structures and Reactivity of Mixed-Ligand Alkyl/Alkoxide Alkali-Metal Magnesiates

Advancing the understanding of using alkali‐metal alkoxides as additives to organomagnesium reagents in Mg−Br exchange reactions, a homologous series of mixed‐ligand alkyl/alkoxide alkali‐metal magnesiates [MMg(CH(2)SiMe(3))(2)(dmem)](2) [dmem=2‐{[2‐(dimethylamino)ethyl]methylamino} ethoxide; M=Li, 1; Na, 2; (THF)K, 3] has been prepared. Structural and spectroscopic studies have established the constitutions of these heteroleptic/heterometallic species, which are retained in arene solution. Evaluation of their reactivity towards 2‐bromoanisole has uncovered a marked alkali‐metal effect with potassium magnesiate 3 being the most efficient of the three ate reagents. Studies probing the constitution of the exchange product from this reaction suggest that the putative [KMgAr(2)(dmem)](2) (Ar=o‐OMe−C(6)H(4)) intermediate undergoes redistribution into its single metal components [KAr](n) and [MgAr(dmem)](2) (5). This process can be circumvented by using a different potassium alkoxide containing an aliphatic chain such as KOR’ (R’=2‐ethylhexyl) which undergoes co‐complexation with Mg(CH(2)SiMe(3)) to give [KMg(CH(2)SiMe(3))(2)(OR’)](2) (7). This ate, in turn, reacts quantitatively with 2‐bromoanisole furnishing [KMgAr(2)(OR’)](2) (9) which is stable in solution as a bimetallic compound. Collectively this work highlights the complexity of these alkali‐metal mediated Mg−Br exchange reactions, where each reaction component can have a profound effect not only on the success of the reaction; but also the stability of the final metalated intermediates prior to their electrophilic interception

Microwave-assisted synthesis and electrochemical evaluation of VO2 (B) nanostructures

Understanding how intercalation materials change during electrochemical operation is paramount to optimizing their behaviour and function and in situ characterization methods allow us to observe these changes without sample destruction. Here we first report the improved intercalation properties of bronze phase vanadium dioxide VO2 (B) prepared by a microwave-assisted route which exhibits a larger electrochemical capacity (232 mAh g-1) compared with VO2 (B) prepared by a solvothermal route (197 mAh g-1). These electrochemical differences have also been followed using in situ X-ray absorption spectroscopy allowing us to follow oxidation state changes as they occur during battery operation

Hydrophosphinylation of Styrenes Catalysed by Well‐Defined s‐Block Bimetallics

Advancing the applications of s-block heterobimetallic complexes in catalysis, we report the use of potassium magnesiate (PMDETA)2K2Mg(CH2SiMe3)4 [PMDETA=N,N,N’,N’,N’’-pentamethyldiethylenetriamine] for the catalytic hydrophosphinylation of styrenes under mild conditions. Exploiting chemical cooperation, this bimetallic approach offers greater catalytic activity and chemoselectivity than the single-metal components KCH2SiMe3 and Mg(CH2SiMe3)2. Stoichiometric studies between (PMDETA)2K2Mg(CH2SiMe3)4 and Ph2P(O)H help to elucidate the constitution of the active catalytic species, and illustrate the influence of donors on the potassium cation coordination, and how this may impact catalytic activity. Mechanistic investigations support that the rate determining step is the insertion of the olefinic substrate

pParticipación ciudadana institucionalizada y organizaciones civiles en Brasil: articulaciones horizontales y verticales en la política de asistencia social

Este artículo se concentra en el impacto de los dispositivos institucionales de participación en las articulaciones entre diversas organizaciones sociales y civiles en Brasil. Tomando el caso de la asistencia social, se argumenta que diversos mecanismos de participación ciudadana institucionalizada, tales como las conferencias y los consejos gestores, impactan positivamente en la generación de una red sectorial “vertical”, donde puede controlarse la política pública desde la federación hasta las localidades, pasando por estados y municipios, y de una red territorial “horizontal”, donde se activan diversas temáticas sectoriales en un mismo territorio. Esta doble articulación permite mayor densidad asociativa, que las redes territoriales tengan mejor conocimiento sobre las políticas sectoriales implementadas en sus ciudades y que las redes sectoriales puedan, además de participar en todos los eslabones de la cadena de la ejecución de la política, conocer sus impactos nacionales y locales.This article focuses on the impact of institutional arrangements for joint participation between different social and civil organizations in Brazil. Taking as a case study the social assistance field, it is argued that various institutionalized mechanisms for citizen participation, such as conferences and management councils tips on generating positive impact of a “vertical” network where public policy can be controlled from the federation to the towns, passing by states and municipalities, and a “horizontal” territorial network where they activate various sectoral themes in the same territory. The double joint allows for greater density of association; to the regional networks have better knowledge on specific policies implemented in their cities and participating in all links of the chain of policy implementation, to know their impacts on the local level.Este artigo se concentra no impacto dos dispositivos institucionais de participação nas articulações entre diversas organizações sociais e civis no Brasil. Tomando o caso da assistência social, argumenta-se que diversos mecanismos de participação cidadã institucionalizada, tais como as conferências e os conselhos gestores, impactam positivamente na geração de uma rede setorial “vertical”, onde pode se controlar a política pública desde a federação até as localidades, passando por estados e municípios, e de uma rede territorial “horizontal”, onde se ativam diversas temáticas setoriais em um mesmo território. Esta dupla articulação permite maior densidade associativa, que as redes territoriais tenham melhor conhecimento sobre as políticas setoriais implementadas em suas cidades e que as redes setoriais possam, além de participar em todos os elos da cadeia da execução da política, conhecer seus impactos nacionais e locais

In situ surface coverage analysis of RuO₂-catalysed HCl oxidation reveals the entropic origin of compensation in heterogeneous catalysis

In heterogeneous catalysis, rates with Arrhenius-like temperature dependence are ubiquitous. Compensation phenomena, which arise from the linear correlation between the apparent activation energy and the logarithm of the apparent pre-exponential factor, are also common. Here, we study the origin of compensation and find a similar dependence on the rate-limiting surface coverage term for each Arrhenius parameter. This result is derived from an experimental determination of the surface coverage of oxygen and chlorine species using temporal analysis of products and prompt gamma activation analysis during HCl oxidation to Cl2 on a RuO2 catalyst. It is also substantiated by theory. We find that compensation phenomena appear when the effect on the apparent activation energy caused by changes in surface coverage is balanced out by the entropic configuration contributions of the surface. This result sets a new paradigm in understanding the interplay of compensation effects with the kinetics of heterogeneously catalysed processes

Incorporation of Non-metal Impurities at the Anatase TiO2_2(001)-(1×\times4) Surface

We use first-principles calculations to investigate the adsorption and incorporation of non-metal impurities (N, C) at the anatase TiO$_2$(001)-(1$\times$4) reconstructed surface. We analyze in detail the influence of the surface structure and local strain on the impurity binding sites and incorporation pathways and identify important intermediates which facilitate impurity incorporation. We find various subsurface interstitial binding sites and corresponding surface $\rightarrow$ subsurface penetration pathways on the reconstructed surface. This surface also favors the presence of subsurface oxygen-vacancies, to which adsorbed species can migrate to form substitutional impurities. Most notably, we show that the non-exposed oxygen sites just below the surface have a key role in the incorporation of nitrogen and carbon in TiO$_2$(001).Comment: 5 figure

Magnesium-mediated arylation of amines via C-F bond activation of fluoroarenes

A series of new Mg(II) amides featuring a bulky β-diketiminate backstop ligand, has been synthesised. These complexes are demonstrated to be excellent sources of nucleophilic amides that can participate in rapid C–F activation of several fluoroarenes at room temperature or using microwave assistance, leading to the installment of synthetically important C–N bonds via nucleophilic substitution

Tasa de éxito subjetivo y objetivo en pacientes operados con cinta suburetral transobturatriz: ocho años de seguimiento

Indexación: Scopus; Scielo.Antecedentes: La Incontinencia Urinaria de Esfuerzo (IOE) representa el 50% de las incontinencias urinarias en la mujer, produciendo un gran impacto en su calidad de vida. Actualmente el TOT es una de las técnicas quirúrgicas más utilizadas para su tratamiento. Objetivos: Determinar la tasa de éxito objetiva y subjetiva de las pacientes operadas por IOE e incontinencia de orina mixta (IOM) mediante TOT, y determinar la tasa de complicaciones perioperatorias. Métodos: Se realizó un estudio retrospectivo de cohorte de 8 años de seguimiento, en el que se evaluó mediante anamnesis, examen físico y protocolos quirúrgicos la tasa de éxito objetivo y subjetivo del TOT. Resultados: La tasa de éxito objetivo y subjetivo fue 92% y 76% respectivamente. El 8,3% de las pacientes presentó alguna complicación y la tasa de exposición de malla fue de 1,2%. Conclusiones: El TOT es una excelente alternativa para el tratamiento de la IOE en el Hospital de Quilpué.http://ref.scielo.org/6tnxn