Interaction between Neisseria gonorrhoeae bacterial peroxidase and its electron donor, the lipid-modified azurin

cofinanced by the ERDF under the PT2020 Partnership Agreement (POCI-01-0145-FEDER-007728).The Neisseria gonorrhoeae bacterial cytochrome c peroxidase plays a key role in detoxifying the cells from H2O2 by reducing it to water using the lipid-modified azurin, LAz, a small type 1 copper protein, as electron donor. Here, the interaction between these two proteins was characterized by steady-state kinetics, two-dimensional NMR and molecular docking simulations. LAz is an efficient electron donor capable of activating this enzyme. This electron transfer complex is weak with a hydrophobic character, with LAz binding close to the electron transferring heme of the enzyme. The high catalytic rate (39 ± 0.03 s−1) is explained by the LAz pre-orientation, due to a positive dipole moment, and by the fast-dynamic ensemble of orientations, suggested by the small chemical shifts.publishersversionpublishe

YhjA - An Escherichia coli trihemic enzyme with quinol peroxidase activity

Belgian Federal Science Policy Office (Belspo) (grant to BD, IAP7/44, iPROS project). co-financed by the ERDF under the PT2020 Partnership Agreement (POCI-01-0145-FEDER-007728).The trihemic bacterial cytochrome c peroxidase from Escherichia coli, YhjA, is a membrane-anchored protein with a C-terminal domain homologous to the classical bacterial peroxidases and an additional N-terminal (NT) heme binding domain. Recombinant YhjA is a 50 kDa monomer in solution with three c-type hemes covalently bound. Here is reported the first biochemical and spectroscopic characterization of YhjA and of the NT domain demonstrating that NT heme is His63/Met125 coordinated. The reduction potentials of P (active site), NT and E hemes were established to be −170 mV, +133 mV and +210 mV, respectively, at pH 7.5. YhjA has quinol peroxidase activity in vitro with optimum activity at pH 7.0 and millimolar range KM values using hydroquinone and menadiol (a menaquinol analogue) as electron donors (KM = 0.6 ± 0.2 and 1.8 ± 0.5 mM H2O2, respectively), with similar turnover numbers (kcat = 19 ± 2 and 13 ± 2 s−1, respectively). YhjA does not require reductive activation for maximum activity, in opposition to classical bacterial peroxidases, as P heme is always high-spin 6-coordinated with a water-derived molecule as distal axial ligand but shares the need for the presence of calcium ions in the kinetic assays. Formation of a ferryl Fe(IV) = O species was observed upon incubation of fully oxidized YhjA with H2O2. The data reported improve our understanding of the biochemical properties and catalytic mechanism of YhjA, a three-heme peroxidase that uses the quinol pool to defend the cells against hydrogen peroxide during transient exposure to oxygenated environments.publishersversionpublishe

Avaliação da interface de colisão e reação (CRI) na remoção de interferentes originados no preparo de amostras de solo por extração sequencial.

A extração sequencial de amostras de solo fornece informações importantes sobre a disponibilidade e mobilidade de elementos traço. A espectrometria de massa com plasma acoplado indutivamente (ICP-MS) é uma técnica analítica adequada para a determinação de elementos presentes em baixas concentrações, porém podem ocorrer interferências severas em meios complexos devido à formação de espécies poliatômicas. Visando corrigir ou eliminar esses efeitos algumas estratégias podem ser adotadas, tais como seleção de isótopos alternativos, correção pelo branco analítico, uso de plasma frio e introdução de gases reacionais e/ou colisionais, como H2 ou He, em celas ou na interface. O objetivo deste trabalho foi avaliar a interface de colisão e reação (CRI) na remoção de interferentes poliatômicos formados a partir do plasma de Ar e dos reagentes utilizados na extração sequencial (BCR) para a determinação de As, Cr e V

Sequential Extraction of Cr, Cu anel V in Soil anel Determination Using ICP·MS.

Among the instrumental techniques that can be useel for eletermination of trace elements in soils inductively coupled plaSl1la mass spectroscopy (ICP-MS) presents aelvantages such as multielemental character and superb sensitivity. However, aspects such as the content of total e1issolveel solids anel the polyatomic íons formeel in complex matrices may limit its application. The determination of Cr. Cu and V may suffer from polyatomic intelierences either originated in the argon plasma 01' in the matrix. In the case of 65Cu+ the main interferents are 23Na40Ar+ anel 23Na40Ca+ The eletermination of 52Cr+ is affecteel by 40Ar12C+ and 51V+ is affected by 35Cl16O+. Notwithstanding, all these elements also have less abundant isotopes not affected by severe interference processes

Prototype and methodology for the characterization of the polymer-calibrator interface heat transfer coefficient

The extrusion of technical thermoplastics profiles generally uses a dry calibration/cooling system, composed by one or several calibrators in series. One of the major difficulties to be faced when modelling this important stage is an adequate prescription of the heat transfer coefficient, hinterface, between the plastic profile surface and the cooling medium, which must include the effect of the interface contact resistance. This is the motivation that led the present research team to develop a prototype calibration system and respective methodology for the characterization of hinterface values which is able to consider a variety of conditions that can be found in extrusion practice. A modular construction was adopted for the calibration system, which allows studying easily the effect of several process parameters. In this work, the developed prototype system is described and its use is illustrated in the determination of hinterface for the production of a polystyrene tape, under specific processing conditions.The authors gratefully acknowledge funding from Fundacao para a Ciencia e a Tecnologia, FCT (COMPETE Program) under the projects FCOMP-01-0124 - FEDER-010190 (Ref. PTDC/EME - MFE1102729/2008) and FCOMP-01-0124 - FEDER-015126 (Ref. FCT PEst-EME-MFE/113988/2009), and FEDER, via FCT, under the PEstC/CTM/LA0025/2011 (Strategic Project - LA 25 - 2011-2012)

Incorporating tool deformation in the design of extrusion dies for complex hollow profiles

The potential of OpenFOAM to design extrusion dies, incorporating the Fluid Structure Interaction (FSI)Fundação para a Ciência e a Tecnologia (FCT) - FCOMP-01-0124-FEDER-015126 (Refª. FCT PTDC/EMEMFE/ 113988/2009), FCOMP-01-0124-FEDER-010190 (Refª. FCT PTDC/EME-FME/102729/2008) and PEst-C/CTM/LA0025/2011 (Strategic Project - LA 25 – 2011-2012), SFRH/BD43632/2008, FCT-SFRH/ BPD/ 77467/ 201

Composition of brazilian phosphate rocks used for cattle feed supplement.

Pbospbate rocks cünstitute lhe bulk of the raw materiaIs for the manufacture fertilizers and some phosphorus b-ased chemicals. !t is well known that natural pbosphate a great varíation of heavy melaIs, and some of lhem, depending of tlleir cOllcentratÍon, present nutritional lmd environmental problems [1]

Extrusion of poly(vinylidene fluoride) recycled filaments : effect of the processing cycles on the degree of crystallinity and electroactive phase content

This study analyses the possibility of reprocessing used poly(vinylidene fluoride), PVDF, maintaining the main properties critical for its use in piezoelectric sensor/actuator applications. The influence of multiple reprocessing cycles of PVDF on crystallinity and ß-phase content fundamental for its electroactive behaviour, was studied. Nine reprocessing cycles were completed and it was found that the material preserved the characteristics required for its use as piezoelectric polymer without significant degradation.The authors thank the Portuguese Foundation for Science and Technology (FCT) (gs1) for financial support under Project Piezotex - PTDC (PTDC/CTM/108801/2008) and in the framework of the Strategic Project PEst-C/FIS/ UI607/20112011, PEst-C/CTM/LA0025/2011 and PEst-C/CTM/UI0264/2011. MPS thanks the FCT for financial support under grant SFRH/BD/70303/2010

Effect of the processing conditions on the mechanical and electrical properties of extruded conductive PP tape and filament

Polypropylene (PP) shows a number of desirable properties that make it a versatile material among thermoplastic polymers. Due to its low cost and density, it is an excellent resin for conductive polymer composites (CPCs).[1] CPCs mainly consist on a polymer matrix with incorporated carbonaceous fillers. These multifunctional materials are routinely employed in various commercial applications due to their good electrical conductivity, corrosion resistance, light weight and enhanced mechanical properties. [2] The filler content is the crucial aspect in conductive polymer composites fabrication: due to mechanical behaviour it must be as low as possible but enough to allow fulfilling the electrical requirements.[2] In this work commercial conductive master batch PP was extruded in the form of tape and filament using different processing conditions, namely different draw ratios and temperatures. In order to tailor the mechanical performance of the material, different several amounts of PP homopolymer were added to the commercial conductive resin. The results show that the amount of homopolymer directly influences mechanical and electrical performance of the material. Increasing homopolymer content yields a more stretchable, and mechanically resistant, material but, on the other hand, reduces its electrical conductivity. This study focuses on the optimization of the processing conditions and composition in order to tailor the mechanical and electrical properties of the material for specific applicationsFundação para a Ciência e a Tecnologia (FCT) - PTDC/CTM/108801/2008, POCI 2010, Pluriannual program

Characterization of the heat transfer coefficient in thermoplastic profile extrusion

The main objective of this work is to design a prototype system that will enable the determination of realistic values for h at the interface polymer-calibrator in real and varied extrusion conditions. The data obtained will allow improving the accuracy of the numerical codes that are being developed by the research team, through the implementation of realistic models for h.FC