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De Souza C.E.,Laboratorio Nacional Of Computac Ao Cientifica | Coutinho D.,Federal University of Santa Catarina
IEEE International Conference on Control and Automation, ICCA

This paper deals with the problem of local stabilization, with a guaranteed stability domain and performance, of open-loop unstable quadratic discrete-time systems. For some polyhedral region of the state-space containing the origin, a method is derived for designing a nonlinear static state feedback controller that ensures an enlarged stability domain for the closed-loop system. The stabilization method is then extended to ensure a quadratic performance for a set of admissible initial states. The controller designs are tailored via finite sets of state-dependent linear matrix inequalities. Numerical examples are presented to illustrate the proposed control designs. © 2011 IEEE. Source

Capriles P.V.S.Z.,Laboratorio Nacional Of Computac Ao Cientifica | Capriles P.V.S.Z.,Federal University of Juiz de fora | Baptista L.P.R.,Laboratorio Nacional Of Computac Ao Cientifica | Baptista L.P.R.,Instituto Oswaldo Cruz | And 5 more authors.
Journal of Molecular Graphics and Modelling

Leishmaniases are caused by protozoa of the genus Leishmania and are considered the second-highest cause of death worldwide by parasitic infection. The drugs available for treatment in humans are becoming ineffective mainly due to parasite resistance; therefore, it is extremely important to develop a new chemotherapy against these parasites. A crucial aspect of drug design development is the identification and characterization of novel molecular targets. In this work, through an in silico comparative analysis between the genomes of Leishmania major and Homo sapiens, the enzyme ribose 5-phosphate isomerase (R5PI) was indicated as a promising molecular target. R5PI is an important enzyme that acts in the pentose phosphate pathway and catalyzes the interconversion of D-ribose-5-phosphate (R5P) and D-ribulose-5-phosphate (5RP). R5PI activity is found in two analogous groups of enzymes called RpiA (found in H. sapiens) and RpiB (found in L. major). Here, we present the first report of the three-dimensional (3D) structures and active sites of RpiB from L. major (LmRpiB) and RpiA from H. sapiens (HsRpiA). Three-dimensional models were constructed by applying a hybrid methodology that combines comparative and ab initio modeling techniques, and the active site was characterized based on docking studies of the substrates R5P (furanose and ring-opened forms) and 5RP. Our comparative analyses show that these proteins are structural analogs and that distinct residues participate in the interconversion of R5P and 5RP. We propose two distinct reaction mechanisms for the reversible isomerization of R5P to 5RP, which is catalyzed by LmRpiB and HsRpiA. We expect that the present results will be important in guiding future molecular modeling studies to develop new drugs that are specially designed to inhibit the parasitic form of the enzyme without significant effects on the human analog. © 2014 Elsevier Inc. All rights reserved. Source

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