Rafael Gonçalves - Academia.edu (original) (raw)
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Papers by Rafael Gonçalves
... Murillo Cavalleiro de Macedo Paulo Vitor Silva Borges Rafael Anderson Gonçalves Suelen Ramona... more ... Murillo Cavalleiro de Macedo Paulo Vitor Silva Borges Rafael Anderson Gonçalves Suelen Ramona de Souza Cunha Heriberto Wagner Amanajás Pena UEPA ... Estes fatores estão ligados, principalmente, ao interesse das pessoas em relação ao produto ou serviço ofertado. ...
Journal of Materials Science, 2008
Electrodes modified with electropolymerized films have received considerable attention in the dev... more Electrodes modified with electropolymerized films have received considerable attention in the development of catalysts and sensors, and their use is rapidly increasing. This work reports modification of the surface of graphite electrodes by electrochemical polymerization of tyramine. These modified electrodes were used to nickel incorporation and hydrogen evolution. Tyramine electrooxidation, in acid and basic media, yielded polymeric films onto graphite surface. In ferrocyanide/ferricyanide solution, the electrodes modified in acid medium showed higher electron transfer efficiency. Impedance studies indicated higher charge transfer resistance to electrodes modified with Ptyr prepared in basic pH. Scanning electron microscopy showed that the formed films present different morphology for the several pH values studied. Interferometry and scanning electron microscopy analysis showed higher coverage to films formed in acid medium. Polymers produced in more alkaline medium present growth self-limited. Nickel was incorporated in the films through immersion of the modified electrodes in solution of potassium hexafluoronickelate, followed of electrochemical reduction of the metal. The electrocatalytic activity of the modified electrodes with nickel incorporated was tested for hydrogen evolution reaction. The amount of nickel mass incorporated as well as the current density of hydrogen evolution reaction was higher in electrodes modified with polytyramine produced in acid medium.
Macromolecular Symposia, 2006
It was observed the formation of polymeric films derived from 4-aminophenol on the graphite elect... more It was observed the formation of polymeric films derived from 4-aminophenol on the graphite electrode in aqueous medium (pH 0.5, 8.0 and 12.0). The electrochemical behavior of formed films was studied by voltammetry cyclic and impedance. These analyses indicate that the preparation in acid medium favors the charge transfer rate of the polymer. Polymers formed at pH 8.0 present higher coverage of the electrode surface and impedance increase. Scanning electron microscopy showed that the formed polymer present globular morphology.
Materials Chemistry and Physics, 2008
Polymer Engineering and Science, 2008
This work describes the preparation of polymers potentiodynamically formed on surface of graphite... more This work describes the preparation of polymers potentiodynamically formed on surface of graphite electrode by anodic oxidation of 2, 3, or 4-aminophenol monomers, as well as incorporation and detection of purine and pyrimidine bases on these modified electrodes. The electrochemical behavior of the formed films was studied by cyclic voltammetry and electrochemical impedance spectroscopy. These analyses indicate that poly-4-aminophenol presents the highest charge transfer rate. The surface morphology was studied by SEM and AFM. These analyses showed that the polymers present globular morphology. The immobilization and detection of purines and pyrimidines on graphite electrodes modified with poly-aminophenols was studied by differential pulse voltammetry. It was possible to show, for the first time, that the oxidation of purine and pyrimidine bases and their mixtures takes place on modified electrodes covered with polymeric films. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Our objective was to analyze the logical articulation between the problem and the theoretical-met... more Our objective was to analyze the logical articulation between the problem and the theoretical-methodological proposal of studies in the field of Special Education, focusing on the epistemological issues. We based our study on the empiric-analytical tendencies, phenomenology-hermeneutic, critical-dialectical and the complexity paradigm. The procedure that was adopted was interpreting all dissertations/thesis produced in Post-Graduate programs in Education and Special Education in Brazil, which focus on Special Education, produced in 2001, 2002 and 2003, available online at CAPES' thesis database. We found empirical, phenomenological and dialectic tendencies. The errors encountered included the failure to include the research among the productions in the field; lack of critical approach; lack of making explicit what educational conception the study was based on; theoretical construction based on different conceptions; lack of coherence in the theoretical-methodological proposals; lack of methodological specification; absence of ethical procedural descriptions; and poorly written abstracts. We came to the conclusion that improvements in theses /dissertations are necessary so as to continually move forward in the production of knowledge in the field of Special Education.
Biological Chemistry, 2008
Lactoferrin (LF) is an iron-binding protein present in several secreted substances, such as milk,... more Lactoferrin (LF) is an iron-binding protein present in several secreted substances, such as milk, and has broad antimicrobial and physiological properties. Because high temperatures may affect protein stability and its functional properties, we investigated the effect of heat on bovine LF structure and stability. The effects of temperatures used during the pasteurization process on LF and its relationship to protein functionality were studied. Conformational changes were monitored using spectroscopic techniques, such as circular dichroism (CD) and fluorescence spectroscopy. The CD data at 70 degrees C showed that LF's secondary structure is drastically and irreversibly affected when the temperature is gradually increased. The same effect is observed when the temperature is gradually raised from 25 degrees C to 105 degrees C and changes are monitored by tryptophan fluorescence emission. We also verified the effects of simulating the pasteurization process; LF remained well structured during the entire process and this result was not time-dependent. Owing to preservation of the secondary structure with changes in the tertiary structure, we thus believe that pasteurization might cause LF to change into an intermediate partially folded state. A better understanding of heat stability is important for the use of LF as a bioactive component in food.
Biochemistry, 2008
Apoptosis is an essential mechanism of cell death required for normal development and homeostasis... more Apoptosis is an essential mechanism of cell death required for normal development and homeostasis of all multicellular organisms. Smac/DIABLO is a dimeric protein important in the control of apoptosis by removing the inhibitory activity of IAPs (inhibitor of apoptosis proteins). In vitro studies reveal that dimerization is required for its function. Here we investigate the structural and thermodynamic features of folding and dimerization of Smac/DIABLO. To disturb the folded, dimeric structure, we used high hydrostatic pressure, low and high temperatures, and chemical denaturing agents. Conformational changes were monitored using spectroscopic techniques such as fluorescence and circular dichroism (CD) as well as gel filtration chromatography. Our data show that Smac/DIABLO is very stable under pressures up to 3.1 kbar, even at subzero temperatures. A complete denaturation/dissociation process is obtained when we use high concentrations of urea, which affect its secondary structure as assessed by CD. The association of pressure and subdenaturing urea concentrations also results in complete denaturation/dissociation of the protein. Under these conditions, unfolding of the protein shows concentration dependence that is in accordance with the dimer-monomer dissociation equilibrium, confirming Smac/DIABLO dissociation. These results suggest that most of the treatments lead to a reversible disruption of the dimeric structure with a dissociation constant ( K d) of 34 x 10 (-21) M (34 zM). This tight dimer is biologically relevant, considering that monomeric mutants bind IAP with low affinity. The extremely high stability of the dimeric form of Smac/DIABLO also implies that once expressed in the cell the protein has a low probability of dissociation and, consequently, loss of function. In addition, the stability in the zeptomolar range is the highest so far measured for a dimeric protein. It also indicates that under most circumstances Smac/DIABLO does not exist as a monomer in the cell and suggests that the dimer-to-monomer equilibrium does not play a regulatory role in the Smac/DIABLO-IAP interaction.
Journal of Molecular Biology, 2007
Biophysical Journal, 1999
Journal of Virological Methods, 2008
Biophysical Chemistry, 2010
The XIAP-BIR3 domain blocks a substantial portion of the apoptosis pathway and is an attractive t... more The XIAP-BIR3 domain blocks a substantial portion of the apoptosis pathway and is an attractive target for novel anticancer agents. The tetrapeptide AVPI, from the protein Smac/DIABLO, binds to the XIAP-BIR3 domain, allowing the cancer cells to die. Here we characterize the binding parameters of AVPI to XIAP-BIR3 and analyze its effects on the thermodynamic stability of this domain. XIAP-BIR3 was exceptionally stable against physical and chemical treatments and became even more stable by interaction with AVPI. Nuclear magnetic resonance experiments demonstrated that conformational selection is taking place upon AVPI interaction with XIAP-BIR3. Molecular dynamics simulations corroborate that the flexibility of XIAP-BIR3 is significantly reduced. The positive binding entropy associated with a loss of conformational entropy involved in the binding indicates that hydrophobic interactions play an important role in the interaction and domain stabilization. The mechanism of XIAP-BIR3 stabilization and its implications for drug affinity optimization are discussed.
... Murillo Cavalleiro de Macedo Paulo Vitor Silva Borges Rafael Anderson Gonçalves Suelen Ramona... more ... Murillo Cavalleiro de Macedo Paulo Vitor Silva Borges Rafael Anderson Gonçalves Suelen Ramona de Souza Cunha Heriberto Wagner Amanajás Pena UEPA ... Estes fatores estão ligados, principalmente, ao interesse das pessoas em relação ao produto ou serviço ofertado. ...
Journal of Materials Science, 2008
Electrodes modified with electropolymerized films have received considerable attention in the dev... more Electrodes modified with electropolymerized films have received considerable attention in the development of catalysts and sensors, and their use is rapidly increasing. This work reports modification of the surface of graphite electrodes by electrochemical polymerization of tyramine. These modified electrodes were used to nickel incorporation and hydrogen evolution. Tyramine electrooxidation, in acid and basic media, yielded polymeric films onto graphite surface. In ferrocyanide/ferricyanide solution, the electrodes modified in acid medium showed higher electron transfer efficiency. Impedance studies indicated higher charge transfer resistance to electrodes modified with Ptyr prepared in basic pH. Scanning electron microscopy showed that the formed films present different morphology for the several pH values studied. Interferometry and scanning electron microscopy analysis showed higher coverage to films formed in acid medium. Polymers produced in more alkaline medium present growth self-limited. Nickel was incorporated in the films through immersion of the modified electrodes in solution of potassium hexafluoronickelate, followed of electrochemical reduction of the metal. The electrocatalytic activity of the modified electrodes with nickel incorporated was tested for hydrogen evolution reaction. The amount of nickel mass incorporated as well as the current density of hydrogen evolution reaction was higher in electrodes modified with polytyramine produced in acid medium.
Macromolecular Symposia, 2006
It was observed the formation of polymeric films derived from 4-aminophenol on the graphite elect... more It was observed the formation of polymeric films derived from 4-aminophenol on the graphite electrode in aqueous medium (pH 0.5, 8.0 and 12.0). The electrochemical behavior of formed films was studied by voltammetry cyclic and impedance. These analyses indicate that the preparation in acid medium favors the charge transfer rate of the polymer. Polymers formed at pH 8.0 present higher coverage of the electrode surface and impedance increase. Scanning electron microscopy showed that the formed polymer present globular morphology.
Materials Chemistry and Physics, 2008
Polymer Engineering and Science, 2008
This work describes the preparation of polymers potentiodynamically formed on surface of graphite... more This work describes the preparation of polymers potentiodynamically formed on surface of graphite electrode by anodic oxidation of 2, 3, or 4-aminophenol monomers, as well as incorporation and detection of purine and pyrimidine bases on these modified electrodes. The electrochemical behavior of the formed films was studied by cyclic voltammetry and electrochemical impedance spectroscopy. These analyses indicate that poly-4-aminophenol presents the highest charge transfer rate. The surface morphology was studied by SEM and AFM. These analyses showed that the polymers present globular morphology. The immobilization and detection of purines and pyrimidines on graphite electrodes modified with poly-aminophenols was studied by differential pulse voltammetry. It was possible to show, for the first time, that the oxidation of purine and pyrimidine bases and their mixtures takes place on modified electrodes covered with polymeric films. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Our objective was to analyze the logical articulation between the problem and the theoretical-met... more Our objective was to analyze the logical articulation between the problem and the theoretical-methodological proposal of studies in the field of Special Education, focusing on the epistemological issues. We based our study on the empiric-analytical tendencies, phenomenology-hermeneutic, critical-dialectical and the complexity paradigm. The procedure that was adopted was interpreting all dissertations/thesis produced in Post-Graduate programs in Education and Special Education in Brazil, which focus on Special Education, produced in 2001, 2002 and 2003, available online at CAPES' thesis database. We found empirical, phenomenological and dialectic tendencies. The errors encountered included the failure to include the research among the productions in the field; lack of critical approach; lack of making explicit what educational conception the study was based on; theoretical construction based on different conceptions; lack of coherence in the theoretical-methodological proposals; lack of methodological specification; absence of ethical procedural descriptions; and poorly written abstracts. We came to the conclusion that improvements in theses /dissertations are necessary so as to continually move forward in the production of knowledge in the field of Special Education.
Biological Chemistry, 2008
Lactoferrin (LF) is an iron-binding protein present in several secreted substances, such as milk,... more Lactoferrin (LF) is an iron-binding protein present in several secreted substances, such as milk, and has broad antimicrobial and physiological properties. Because high temperatures may affect protein stability and its functional properties, we investigated the effect of heat on bovine LF structure and stability. The effects of temperatures used during the pasteurization process on LF and its relationship to protein functionality were studied. Conformational changes were monitored using spectroscopic techniques, such as circular dichroism (CD) and fluorescence spectroscopy. The CD data at 70 degrees C showed that LF's secondary structure is drastically and irreversibly affected when the temperature is gradually increased. The same effect is observed when the temperature is gradually raised from 25 degrees C to 105 degrees C and changes are monitored by tryptophan fluorescence emission. We also verified the effects of simulating the pasteurization process; LF remained well structured during the entire process and this result was not time-dependent. Owing to preservation of the secondary structure with changes in the tertiary structure, we thus believe that pasteurization might cause LF to change into an intermediate partially folded state. A better understanding of heat stability is important for the use of LF as a bioactive component in food.
Biochemistry, 2008
Apoptosis is an essential mechanism of cell death required for normal development and homeostasis... more Apoptosis is an essential mechanism of cell death required for normal development and homeostasis of all multicellular organisms. Smac/DIABLO is a dimeric protein important in the control of apoptosis by removing the inhibitory activity of IAPs (inhibitor of apoptosis proteins). In vitro studies reveal that dimerization is required for its function. Here we investigate the structural and thermodynamic features of folding and dimerization of Smac/DIABLO. To disturb the folded, dimeric structure, we used high hydrostatic pressure, low and high temperatures, and chemical denaturing agents. Conformational changes were monitored using spectroscopic techniques such as fluorescence and circular dichroism (CD) as well as gel filtration chromatography. Our data show that Smac/DIABLO is very stable under pressures up to 3.1 kbar, even at subzero temperatures. A complete denaturation/dissociation process is obtained when we use high concentrations of urea, which affect its secondary structure as assessed by CD. The association of pressure and subdenaturing urea concentrations also results in complete denaturation/dissociation of the protein. Under these conditions, unfolding of the protein shows concentration dependence that is in accordance with the dimer-monomer dissociation equilibrium, confirming Smac/DIABLO dissociation. These results suggest that most of the treatments lead to a reversible disruption of the dimeric structure with a dissociation constant ( K d) of 34 x 10 (-21) M (34 zM). This tight dimer is biologically relevant, considering that monomeric mutants bind IAP with low affinity. The extremely high stability of the dimeric form of Smac/DIABLO also implies that once expressed in the cell the protein has a low probability of dissociation and, consequently, loss of function. In addition, the stability in the zeptomolar range is the highest so far measured for a dimeric protein. It also indicates that under most circumstances Smac/DIABLO does not exist as a monomer in the cell and suggests that the dimer-to-monomer equilibrium does not play a regulatory role in the Smac/DIABLO-IAP interaction.
Journal of Molecular Biology, 2007
Biophysical Journal, 1999
Journal of Virological Methods, 2008
Biophysical Chemistry, 2010
The XIAP-BIR3 domain blocks a substantial portion of the apoptosis pathway and is an attractive t... more The XIAP-BIR3 domain blocks a substantial portion of the apoptosis pathway and is an attractive target for novel anticancer agents. The tetrapeptide AVPI, from the protein Smac/DIABLO, binds to the XIAP-BIR3 domain, allowing the cancer cells to die. Here we characterize the binding parameters of AVPI to XIAP-BIR3 and analyze its effects on the thermodynamic stability of this domain. XIAP-BIR3 was exceptionally stable against physical and chemical treatments and became even more stable by interaction with AVPI. Nuclear magnetic resonance experiments demonstrated that conformational selection is taking place upon AVPI interaction with XIAP-BIR3. Molecular dynamics simulations corroborate that the flexibility of XIAP-BIR3 is significantly reduced. The positive binding entropy associated with a loss of conformational entropy involved in the binding indicates that hydrophobic interactions play an important role in the interaction and domain stabilization. The mechanism of XIAP-BIR3 stabilization and its implications for drug affinity optimization are discussed.