Search

This paper presents the design and implementation of a multivariable system control for a productive process of drying of wet product on a Jet dryer, using PI controllers and simplified decoupling. The main goal of this implementation is to reduce the amount of non-compliant product that is generated at a company in the mining sector, for manual manipulation of input and output variables, by the strong interaction between them and the effect of the disturbances in the process that generated losses both in time and in the product. For the design, an identification of the process was carried out, then the PI controllers were estimated offline and finally the decoupling design was made. The results yielded from the simulation and the implementation in the process demonstrated the effectiveness of the designed control system. En este articulo se presenta el diseno e implementacion de un sistema de control multivariable para un proceso productivo de secado de producto humedo en un secador a chorro, utilizando controladores PI y desacopladores de tipo simplificado. El objetivo principal de esta implementacion es reducir la cantidad de producto no conforme que se genera en una compania del sector minero, por la manipulacion manual de las variables de entrada y de salida, por la fuerte interaccion entre ellas y por el efecto de las perturbaciones en el proceso que generan perdidas tanto en tiempo como en el producto. Para el diseno se realizo la identificacion del proceso, se estimaron los controladores PI fuera de linea y, finalmente se realizo el diseno de los desacopladores. Los resultados obtenidos a escala de simulacion y en el proceso real demostraron la efectividad del sistema de control disenado.

En este artículo se presenta el diseño e implementación de un sistema de control multivariable para un proceso productivo de secado de producto húmedo en un secador a chorro, utilizando controladores PI y desacopladores de tipo simplificado. El objetivo principal de esta implementación es reducir la cantidad de producto no conforme que se genera en una compañía del sector minero, por la manipulación manual de las variables de entrada y de salida, por la fuerte interacción entre ellas y por el efecto de las perturbaciones en el proceso que generan pérdidas tanto en tiempo como en el producto. Para el diseño se realizó la identificación del proceso, se estimaron los controladores PI fuera de línea y, finalmente se realizó el diseño de los desacopladores. Los resultados obtenidos a escala de simulación y en el proceso real demostraron la efectividad del sistema de control diseñado.

The alkane hydroxylase system of Pseudomonas putida GPo1 allows it to use alkanes as the sole source of carbon and energy. Bacterial alkane hydroxylases have tremendous potential as biocatalysts for the stereo- and regioselective transformation of a wide range of chemically inert unreactive alkanes into valuable reactive chemical precursors. We have produced and characterized the first 2-dimensional crystals of the integral membrane component of the P. putida alkane hydroxylase system, the nonheme di-iron alkane monooxygenase AlkB. Our analysis reveals for the first time that AlkB reconstituted into a lipid bilayer forms trimers. Addition of detergents that do not disrupt the AlkB oligomeric state (decyl maltose neopentyl glycol [DMNG], lauryl maltose neopentyl glycol [LMNG], and octaethylene glycol monododecyl ether [C 12 E 8 ]) preserved its activity at a level close to that of the detergent-free control sample. In contrast, the monomeric form of AlkB produced by purification in n -decyl-β- d -maltopyranoside (DM), n -dodecyl-β- d -maltopyranoside (DDM), octyl glucose neopentyl glycol (OGNG), and n -dodecyl- N , N -dimethylamine- N -oxide (LDAO) was largely inactive. This is the first indication that the physiologically active form of membrane-embedded AlkB may be a multimer. We present for the first time experimental evidence that 1-octyne acts as a mechanism-based inhibitor of AlkB. Therefore, despite the lack of any significant full-length sequence similarity with members of other monooxygenase classes that catalyze the terminal oxidation of alkanes, AlkB is likely to share a similar catalytic mechanism.

In photosynthesis Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) catalyses the often rate limiting CO2-fixation step in the Calvin cycle. This makes Rubisco both the gatekeeper for carbon entry into the biosphere and a target for functional improvement to enhance photosynthesis and plant growth. Encumbering the catalytic performance of Rubisco is its highly conserved, complex catalytic chemistry. Accordingly, traditional efforts to enhance Rubisco catalysis using protracted “trial and error” protein engineering approaches have met with limited success. Here we demonstrate the versatility of high throughput directed (laboratory) protein evolution for improving the carboxylation properties of a non-photosynthetic Rubisco from the archaea Methanococcoides burtonii. Using chloroplast transformation in the model plant Nicotiana tabacum (tobacco) we confirm the improved forms of M. burtonii Rubisco increased photosynthesis and growth relative to tobacco controls producing wild-type M. burtonii Rubisco. Our findings indicate continued directed evolution of archaeal Rubisco offers new potential for enhancing leaf photosynthesis and plant growth.

Improving global yields of important agricultural crops is a complex challenge. Enhancing yield and resource use by engineering improvements to photosynthetic carbon assimilation is one potential solution. During the last 40 million years C 4 photosynthesis has evolved multiple times, enabling plants to evade the catalytic inadequacies of the CO 2 -fixing enzyme, ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco). Compared with their C 3 ancestors, C 4 plants combine a faster rubisco with a biochemical CO 2 -concentrating mechanism, enabling more efficient use of water and nitrogen and enhanced yield. Here we show the versatility of plastome manipulation in tobacco for identifying sequences in C 4 -rubisco that can be transplanted into C 3 -rubisco to improve carboxylation rate ( V C ). Using transplastomic tobacco lines expressing native and mutated rubisco large subunits (L-subunits) from Flaveria pringlei (C 3 ), Flaveria floridana (C 3 -C 4 ), and Flaveria bidentis (C 4 ), we reveal that Met-309-Ile substitutions in the L-subunit act as a catalytic switch between C 4 ( 309 Ile; faster V C , lower CO 2 affinity) and C 3 ( 309 Met; slower V C , higher CO 2 affinity) catalysis. Application of this transplastomic system permits further identification of other structural solutions selected by nature that can increase rubisco V C in C 3 crops. Coengineering a catalytically faster C 3 rubisco and a CO 2 -concentrating mechanism within C 3 crop species could enhance their efficiency in resource use and yield.

Bacterial alkane hydroxylases are of high interest for bioremediation applications as they allow some bacteria to grow in oil-contaminated environments. Furthermore, they have tremendous biotechnological potential as they catalyse the stereo- and regio-specific hydroxylation of chemically inert alkanes, which can then be used in the synthesis of pharmaceuticals and other high-cost chemicals. Despite their potential, progress on the detailed characterization of these systems has so far been slow mainly due to the lack of a robust procedure to purify its membrane protein component, monooxygenase AlkB, in a stable and active form. This study reports a new method for isolating milligramme amounts of recombinant Pseudomonas putida GPo1 AlkB in a folded, catalytically active form to purity levels above 90%. AlkB solubilised and purified in the detergent lauryldimethylamine oxide was demonstrated to be active in catalysing the epoxidation reaction of 1-octene with an estimated K (m) value of 0.2 mM.

There is a growing impetus in developing novel strategies to address global concerns regarding food security. As crop productivity gains through traditional breeding begin to lag and arable land becomes scarcer, it seems that we are heading for unsustainable global populations. It has been

Like many enzymes, the biogenesis of the multi-subunit CO(2)-fixing enzyme ribulose-1,5-bisphosphate (RuBP) carboxylase/oxygenase (Rubisco) in different organisms requires molecular chaperones. When expressed in Escherichia coli, the large (L) subunits of the Rubisco from the archaeabacterium Methanococcoides burtonii assemble into functional dimers (L(2)). However, further assembly into pentamers of L(2) (L(10)) occurs when expressed in tobacco chloroplasts or E. coli producing RuBP. In vitro analyses indicate that the sequential assembly of L(2) into L(10) (via detectable L(4) and L(6) intermediates) occurs without chaperone involvement and is stimulated by protein rearrangements associated with either the binding of substrate RuBP, the tight binding transition state analog carboxyarabinitol-1,5-bisphosphate, or inhibitory divalent metal ions within the active site. The catalytic properties of L(2) and L(10) M. burtonii Rubisco (MbR) were indistinguishable. At 25 degrees C they both shared a low specificity for CO(2) over O(2) (1.1 mol x mol(-1)) and RuBP carboxylation rates that were distinctively enhanced at low pH (approximately 4 s(-1) at pH 6, relative to 0.8 s(-1) at pH 8) with a temperature optimum of 55 degrees C. Like other archaeal Rubiscos, MbR also has a high O(2) affinity (K(m)(O(2)) = approximately 2.5 microM). The catalytic and structural similarities of MbR to other archaeal Rubiscos contrast with its closer sequence homology to bacterial L(2) Rubisco, complicating its classification within the Rubisco superfamily.

Key to the virulence of apicomplexan parasites is their ability to move through tissue and to invade and egress from host cells. Apicomplexan motility requires the activity of the glideosome, a multicomponent molecular motor composed of a type XIV myosin, MyoA. Here we identify a novel glideosome component, essential light chain 2 (ELC2), and functionally characterize the two essential light chains (ELC1 and ELC2) of MyoA in Toxoplasma. We show that these proteins are functionally redundant but are important for invasion, egress, and motility. Molecular simulations of the MyoA lever arm identify a role for Ca2+ in promoting intermolecular contacts between the ELCs and the adjacent MLC1 light chain to stabilize this domain. Using point mutations predicted to ablate either the interaction with Ca2+ or the interface between the two light chains, we demonstrate their contribution to the quality, displacement, and speed of gliding Toxoplasma parasites. Our work therefore delineates the importance of the MyoA lever arm and highlights a mechanism by which this domain could be stabilized in order to promote invasion, egress, and gliding motility in apicomplexan parasites., IMPORTANCE Tissue dissemination and host cell invasion by apicomplexan parasites such as Toxoplasma are pivotal to their pathogenesis. Central to these processes is gliding motility, which is driven by an actomyosin motor, the MyoA glideosome. Others have demonstrated the importance of the MyoA glideosome for parasite motility and virulence in mice. Disruption of its function may therefore have therapeutic potential, and yet a deeper mechanistic understanding of how it works is required. Ca2+-dependent and -independent phosphorylation and the direct binding of Ca2+ to the essential light chain have been implicated in the regulation of MyoA activity. Here we identify a second essential light chain of MyoA and demonstrate the importance of both to Toxoplasma motility. We also investigate the role of Ca2+ and the MyoA regulatory site in parasite motility and identify a potential mechanism whereby binding of a divalent cation to the essential light chains could stabilize the myosin to allow productive movement.

The introduction and wide use of antibacterial drugs has resulted in the emergence of resistant organisms. DfrB dihydrofolate reductase (DHFR) is a bacterial enzyme that is uniquely associated with mobile gene cassettes within integrons, and confers resistance to the drug trimethoprim. This enzyme has intrigued microbiologists since it was discovered more than thirty years ago because of its simple structure, enzymatic inefficiency and its virtual insensitivity to trimethoprim. Here, for the first time, a comprehensive discussion of genetic, evolutionary, structural and functional studies of this enzyme is presented together. This information supports the ideas that DfrB DHFR is a poorly adapted catalyst and has recently been recruited to perform a novel enzymatic activity in response to selective pressure.

R67 dihydrofolate reductase (DHFR), a bacterial plasmid-encoded enzyme associated with resistance to the drug trimethoprim, shows neither sequence nor structural homology with the chromosomal DHFR. It presents a highly symmetrical toroidal structure, where four identical monomers contribute to the unique central active-site pore. Two reactants (dihydrofolate, DHF), two cofactors (NADPH) or one of each (R67*DHF*NADPH) can be found simultaneously within the active site, the last one being the reactive ternary complex. As the positioning of the ligands has proven elusive to empirical determination, we addressed the problem from a theoretical perspective. Several potential structures of the ternary complex were generated using the docking programs AutoDock and FlexX. The variability among the final poses, many of which conformed to experimental data, prompted us to perform a comparative scoring analysis and molecular dynamics simulations to assess the stability of the complexes. Analysis of ligand-ligand and ligand-protein interactions along the 4 ns trajectories of eight different structures allowed us to identify important inter-ligand contacts and key protein residues. Our results, combined with published empirical data, clearly suggest that multipe binding modes of the ligands are possible within R67 DHFR. While the pterin ring of DHF and the nicotinamide ring of NADPH assume a stacked endo-conformation at the centre of the pore, probably assisted by V66, Q67 and I68, the tails of the molecules extend towards opposite ends of the cavity, adopting multiple configurations in a solvent rich-environment where hydrogen-bond interactions with K32 and Y69 may play important roles.

Pseudomonas putida GPo1 alkane hydroxylase (AlkB) is an integral membrane protein that catalyses the hydroxylation of medium-chain alkanes (C3–C12). 1-Octyne irreversibly inhibits this non-haem di-iron mono-oxygenase under turnover conditions, suggesting that it acts as a mechanism-based inactivator. Upon binding to the active site, 1-octyne is postulated to be oxidized to an oxirene that rapidly rearranges to a reactive ketene which covalently acylates nearby residues, resulting in enzyme inactivation. In analysis of inactivated AlkB by LC–MS/MS, several residues exhibited a mass increase of 126.1 Da, corresponding to the octanoyl moiety derived from oxidative activation of 1-octyne. Mutagenesis studies of conserved acylated residues showed that Lys18 plays a critical role in enzyme function, as a single-point mutation of Lys18 to alanine (K18A) completely abolished enzymatic activity. Finally, we present a computational 3D model structure of the transmembrane domain of AlkB, which revealed the overall packing arrangement of the transmembrane helices within the lipid bilayer and the location of the active site mapped by the 1-octyne modifications.

The CagA protein of Helicobacter pylori is associated with increased virulence and gastric cancer risk. CagA is translocated into the host cell by a H. pylori type IV secretion system via mechanisms that are poorly understood. Translocated CagA interacts with numerous host factors, altering a variety of host signalling pathways. The recently determined crystal structure of C-terminally-truncated CagA indicated the presence of two domains: the smaller, flexible N-terminal domain and the larger, middle domain. In this study, we have investigated the conformation, oligomeric state and stability of the N-terminal, middle and glutamate-proline-isoleucine-tyrosine-alanine (EPIYA)-repeats domains. All three domains are monomeric, suggesting that the multimerisation of CagA observed in infected cells is likely to be mediated not by CagA itself but by its interacting partners. The middle and the C-terminal domains, but not the N-terminal domain, are capable of refolding spontaneously upon heat denaturation, lending support to the hypothesis that unfolded CagA is threaded C-terminus first through the type IV secretion channel with its N-terminal domain, which likely requires interactions with other domains to refold, being threaded last. Our findings also revealed that the C-terminal EPIYA-repeats domain of CagA exists in an intrinsically disordered premolten globule state with regions in PPII conformation - a feature that is shared by many scaffold proteins that bind multiple protein components of signalling pathways. Taken together, these results provide a deeper understanding of the physicochemical properties of CagA that underpin its complex cellular and oncogenic functions.

Rubisco (ribulose-1,5-bisphosphate (RuBP) carboxylase/oxygenase) enables net carbon fixation through the carboxylation of RuBP. However, some characteristics of Rubisco make it surprisingly inefficient and compromise photosynthetic productivity. For example, Rubisco catalyses a wasteful reaction with oxygen that leads to the release of previously fixed CO(2) and NH(3) and the consumption of energy during photorespiration. Furthermore, Rubisco is slow and large amounts are needed to support adequate photosynthetic rates. Consequently, Rubisco has been studied intensively as a prime target for manipulations to 'supercharge' photosynthesis and improve both productivity and resource use efficiency. The catalytic properties of Rubiscos from diverse sources vary considerably, suggesting that changes in turnover rate, affinity, or specificity for CO(2) can be introduced to improve Rubisco performance in specific crops and environments. While attempts to manipulate plant Rubisco by nuclear transformation have had limited success, modifying its catalysis by targeted changes to its catalytic large subunit via chloroplast transformation have been much more successful. However, this technique is still in need of development for most major food crops including maize, wheat, and rice. Other bioengineering approaches for improving Rubisco performance include improving the activity of its ancillary protein, Rubisco activase, in addition to modulating the synthesis and degradation of Rubisco's inhibitory sugar phosphate ligands. As the rate-limiting step in carbon assimilation, even modest improvements in the overall performance of Rubisco pose a viable pathway for obtaining significant gains in plant yield, particularly under stressful environmental conditions.

Methyltetrahydrofolate:corrinoid/iron-sulfur protein methyltransferase (MeTr) catalyzes the transfer of the N5-methyl group from N5-methyltetrahydrofolate (CH(3)THF) to the cobalt center of a corrinoid/iron-sulfur protein, a reaction similar to that of cobalamin-dependent methionine synthase (MetH). For such a reaction to occur, CH(3)THF is expected to be activated by a stereospecific protonation at the N5 position. It has been shown experimentally that binding to MeTr is associated with a pK(a) increase and proton uptake. The enzyme could achieve this by binding the unprotonated form of CH(3)THF, followed by specific protonation at the correct orientation. Here we have used computational approaches to investigate the protonation state of the ligand and active-site residues in MeTr. First, quantum mechanical (QM) methods with the PCM solvation model were used to predict protonation positions and pK(a) values of pterin, folate, and their analogues in an aqueous environment. After a reliable calibration of computational and experimental results was obtained, the effect of the protein environment was then considered. Different protonation states of CH(3)THF and active-site aspartic residues (D75 and D160) were investigated using QM calculations of active-site fragment complexes and the perturbed quantum atom (PQA) approach within QM/MM simulations. The final free energy results indicate that the N5 position of the tetrahydropterin ring is the preferred protonation position of CH(3)THF when bound to the active site of MeTr, followed by Asp160. We also found that the active-site environment is likely to increase the pK(a) of N5 by about 3 units, leading to proton uptake upon CH(3)THF binding, as observed experimentally for MeTr. Some implications of the results are discussed for the MetH mechanism.

A rational approach is needed to maximize the chances of finding new drugs, and to exploit the opportunities of potential new drug targets emerging from genomic and proteomic initiatives, and from the large libraries of small compounds now readily available through combinatorial chemistry. Despite a shaky early history, computer-aided drug design techniques can now be effective in reducing costs and speeding up drug discovery. This happy outcome results from development of more accurate and reliable algorithms, use of more thoughtfully planned strategies to apply them, and greatly increased computer power to allow studies with the necessary reliability to be performed. Our review focuses on applications and protocols, with the main emphasis on critical analysis of recent studies where docking calculations and molecular dynamics (MD) simulations were combined to dock small molecules into protein receptors. We highlight successes to demonstrate what is possible now, but also point out drawbacks and future directions. The review is structured to lead the reader from the simpler to more compute-intensive methods. Thus, while inexpensive and fast docking algorithms can be used to scan large compound libraries and reduce their size, more accurate but expensive MD simulations can be applied when a few selected ligand candidates remain. MD simulations can be used: during the preparation of the protein receptor before docking, to optimize its structure and account for protein flexibility; for the refinement of docked complexes, to include solvent effects and account for induced fit; to calculate binding free energies, to provide an accurate ranking of the potential ligands; and in the latest developments, during the docking process itself to find the binding site and correctly dock the ligand a priori.

La profesión docente está profundamente afectada por los cambios científicos, tecnológicos, económicos, sociales y culturales que se dan en la sociedad actual1. Las escuelas de hoy exigen por parte del alumnado, de las familias, de las fuerzas sociales y de la administración constantes demandas. Todo esto conlleva a que los docentes se encuentren ante exigencias cada vez mayores y conflictivas, ya que, han de ser transmisores y a la vez críticos de la educación ante las nuevas generaciones. Se les pide integrar socialmente a los alumnos como miembros comprometidos y responsables en una sociedad que constantemente está cambiando y expuesta a continuas crisis económicas y sociales con altas tasas de competitividad, agresividad, injusticias y exclusión. También se pretende que los docentes sean agentes amortiguadores de las desigualdades sociales y de las deficiencias personales al integrar al alumnado con necesidades educativas especiales en un sistema único de enseñanza. Sumado a esto, que deben estar en permanente actualización2 Todo esto coloca al docente ante una situación de alto riesgo de estrés laboral que puede tener consecuencias para su salud. La enseñanza ha sido considerada como una ocupación particularmente estresante, pues, los riesgos psicosociales perjudican la salud de los trabajadores, causando estrés y a largo plazo problemas de salud reflejado en enfermedades, como problemas cardiovasculares, respiratorias, inmunitarias, gastrointestinales, dermatológicas, musculoesqueléticas, mentales, entre otras3. El estrés laboral se reconoce como un problema de gran magnitud que afecta el ámbito educativo y el desempeño de los docentes. Por tanto, es necesario identificar los factores de riesgo asociados a este, en el contexto de los docentes. Teniendo en cuenta la importancia que cobra cada vez más la afectación de los factores de riesgo psicosocial de trabajo en la salud de los docentes y el incremento gradual de los niveles de estrés en ellos, surge la motivación de conocer la posible relación que tienen los factores de riesgo psicosocial con los niveles de estrés en los docentes de una institución de educación pública ubicada en la ciudad de Palmira. Es fundamental brindar la atención necesaria a la seguridad, salud y bienestar de los docentes con el fin de que puedan ejercer sus funciones en un ambiente saludable que promueva el bienestar mental y físico previniendo el estrés inadecuado perjudicando la salud. Maestría MAGISTER EN SALUD OCUPACIONAL

Submitted by Francisco Batista de Medeiros (francisco.medeiros@ifrn.edu.br) on 2016-03-02T02:13:53Z No. of bitstreams: 1 FranciscoMedeiros_TESE.pdf: 1201195 bytes, checksum: c5f360d0b3f1e80e38f01dea5b13f747 (MD5) Approved for entry into archive by Jose Yvan Pereira Leite (jyp.leite@ifrn.edu.br) on 2016-03-02T09:30:00Z (GMT) No. of bitstreams: 1 FranciscoMedeiros_TESE.pdf: 1201195 bytes, checksum: c5f360d0b3f1e80e38f01dea5b13f747 (MD5) Made available in DSpace on 2016-03-02T09:30:00Z (GMT). No. of bitstreams: 1 FranciscoMedeiros_TESE.pdf: 1201195 bytes, checksum: c5f360d0b3f1e80e38f01dea5b13f747 (MD5) Previous issue date: 2014-11-28 Apresentamos neste trabalho uma definição de complexidade na categoria derivada de complexos (limitados superiormente) de módulos sobre uma k-álgebra de dimensão finita. Um dos resultados que conseguimos foi uma relação entre a complexidade de objetos indecomponíveis e a noção de dimensão global forte. Mais especificamente, mostramos que a existência de um objeto indecomponível na categoria derivada limitada superiormente com complexidade não nula é condição suficiente para que a respectiva álgebra tenha dimensão global forte infinita. Também investigamos se existe uma relação entre as dimensões global e global forte da classe das álgebras shod (Coelho e Lanzilotta, 2009). Fomos motivados pela caracterização da classe das álgebras quase inclinadas (Happel, Reiten e Smalo, 1996) em termos da sua dimensão global forte, dada por D. Happel e D. Zacharia (2008), e pelo fato das álgebras shod serem uma generalização das álgebras quase inclinadas. Nossa conclusão foi que não existe, em geral, uma caracterização das álgebras shod em termos de sua dimensão global forte. Isto é, mostramos que para cada inteiro d > 2 existe uma álgebra shod estrita cuja dimensão global forte é igual a d. We introduce in this thesis a definition of complexity in the derived category of bounded above complexes of modules over a finite dimensional k-algebra. One of our result shows a relationship between the complexity of indecomposable objects and the notion of strong global dimension. More specifically, we prove that the existence of an indecomposable object in the category derived bounded above whose complexity is not zero is a sufficient condition for corresponding algebra being of infinite strong global dimension. We also investigate the existence of a relationship between the global dimension and the strong global dimension of shod algebras (Coelho and Lanzilotta, 1999). Our motivation came from characterization of quasitilted algebras (Happel, Reiten and Smalo, 1996) by its strong global dimension, given by D. Happel and D. Zacharia (2008), and from the fact that shod algebras are a generalization of quasitilted algebras. Our conclusion was that there is not in general a characterization of shod algebras in terms of its strong global dimension. This conclusion comes from the fact that we showed that for each integer d > 2 there exists a strictly shod algebra whose strong global dimension is d.