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Selective antibacterial activity of the cationic peptide PaDBS1R6 against Gram-negative bacteria
(2019) Fensterseifer, Isabel Cristina Marques; Felício, Mário Romão; Alves, Eliane Santana Fernandes; Cardoso, Marlon Henrique e Silva; Torres, Marcelo Der Torossian; Matos, Carolina Oliveira; Silva, Osmar Nascimento; Lu, Timothy K. T.; Freire, Maurício Vilela; Neves, Natan de Carvalho; Liao, Luciano Morais
Infections caused by Gram-negative bacteria, Escherichia coli and Pseudomonas aeruginosa foremost among them, constitute a major worldwide health problem. Bioinformatics methodologies are being used to rationally design new antimicrobial peptides, a potential alternative for treating these infections. One of the algorithms used to develop antimicrobial peptides is the Joker, which was used to design the peptide PaDBS1R6. This study evaluates the antibacterial activities of PaDBS1R6 in vitro and in vivo, characterizes the peptide interaction to target membranes, and investigates the PaDBS1R6 structure in contact with mimetic vesicles. Moreover, we demonstrate that PaDBS1R6 exhibits selective antimicrobial activity against Gram-negative bacteria. In the presence of negatively charged and zwitterionic lipids the structural arrangement of PaDBS1R6 transits from random coil to α-helix, as characterized by circular dichroism. The tertiary structure of PaDBS1R6 was determined by NMR in zwitterionic dodecylphosphocholine (DPC) micelles. In conclusion, PaDBS1R6 is a candidate for the treatment of nosocomial infections caused by Gram-negative bacteria, as template for producing other antimicrobial agents.
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Fast and potent bactericidal membrane lytic activity of PaDBS1R1, a novel cationic antimicrobial peptide
(2019) Irazazabal, Luz Noemí; Porto, William Farias; Fensterseifer, Isabel Cristina Marques; Alves, Eliane Santana Fernandes; Matos, Carolina Oliveira; Menezes, Antônio Severo; Felício, Mário Romão; Gonçalves, Sónia; Santos, Nuno C.; Ribeiro, Suzana Meira; Humblot, Vincent; Liao, Luciano Morais; Ladram, Ali; Franco, Octávio Luiz
Antimicrobial peptides (AMPs) are promising candidates for the development of future antibiotics. In an attempt to increase the efficacy of therapeutic AMPs, computer-based design methods appear as a reliable strategy. In this study, we evaluated the antimicrobial efficiency and mechanism of action of a novel designed AMP named PaDBS1R1, previously designed by means of the Joker algorithm, using a fragment of the ribosomal protein L39E from the archaeon Pyrobaculum aerophilum as a template. PaDBS1R1 displayed low micromolar broad-spectrum antimicrobial activity against Gram-negative (MIC of 1.5 μM) and Gram-positive (MIC of 3 μM) bacteria, including carbapenem-resistant Klebsiella pneumoniae (MIC of 6.25 μM) and methicillin-resistant Staphylococcus aureus (MIC of 12.5 μM), without cytotoxicity towards HEK-293 cells. In addition, membrane permeabilization and depolarization assays, combined with time-kill studies and FEG-SEM imaging, indicated a fast membrane permeation and further leakage of intracellular content. Biophysical studies with lipid vesicles show a preference of PaDBS1R1 for Gram-negative bacteria-like membranes. We investigated the three-dimensional structure of PaDBS1R1 by CD and NMR analyses. Our results suggest that PaDBS1R1 adopts an amphipathic α-helix upon interacting with hydrophobic environments, after an initial electrostatic interaction with negative charges, suggesting a membrane lytic effect. This study reveals that PaDBS1R1 has potential application in antibiotic therapy.
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Redesign da Petrobras: uma abordagem para reconstrução da confiança e da reputação da marca
(Universidade Federal de Goiás, 2024-01-15) Venâncio Filho, André Pereira; Rocha, Marcio Alves da; Rocha, Marcio Alves da; Oliveira, Flavio Gomes de; Canfield, Daniel de Salles
This capstone project seeks to comprehend the pivotal role of a designer in a redesign initiative that is in harmony with crisis management, aiming to rejuvenate a brand’s reputation. The endeavor integrates the application of time-honored theories of brand design and participatory design techniques, intending to forge a bond with the target demographic, spanning millions of individuals in Brazil and beyond. In essence, this study advocates for the rebranding of Petrobras, the preeminent corporation in the oil and derivatives sector in Latin America.
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Membrane interactions of the anuran antimicrobial peptide HSP1-NH2: different aspects of the association to anionic and zwitterionic biomimetic systems
(2021) Gomes, Isabela Pereira; Santos, Talita Lopes dos; Souza, Amanda Neves de; Nunes, Lúcio Otávio; Cardoso, Gabriele de Azevedo; Matos, Carolina Oliveira; Torres, Lívia Mara Fontes Costa; Liao, Luciano Morais; Resende, Jarbas Magalhães; Verly, Rodrigo Moreira
Studies have suggested that antimicrobial peptides act by different mechanisms, such as micellisation, self-assembly of nanostructures and pore formation on the membrane surface. This work presents an extensive investigation of the membrane interactions of the 14 amino-acid antimicrobial peptide hylaseptin P1-NH2 (HSP1-NH2), derived from the tree-frog Hyla punctata, which has stronger antifungal than antibacterial potential. Biophysical and structural analyses were performed and the correlated results were used to describe in detail the interactions of HSP1-NH2 with zwitterionic and anionic detergent micelles and phospholipid vesicles. HSP1-NH2 presents similar well-defined helical conformations in both zwitterionic and anionic micelles, although NMR spectroscopy revealed important structural differences in the peptide N-terminus. 2H exchange experiments of HSP1-NH2 indicated the insertion of the most N-terminal residues (1–3) in the DPC-d38 micelles. A higher enthalpic contribution was verified for the interaction of the peptide with anionic vesicles in comparison with zwitterionic vesicles. The pore formation ability of HSP1-NH2 (examined by dye release assays) and its effect on the size and surface charge as well as on the lipid acyl chain ordering (evaluated by Fourier-transform infrared spectroscopy) of anionic phospholipid vesicles showed membrane disruption even at low peptide-to-phospholipid ratios, and the effect increases proportionately to the peptide concentration. On the other hand, these biophysical investigations showed that a critical peptide-to-phospholipid ratio around 0.6 is essential for promoting disruption of zwitterionic membranes. In conclusion, this study demonstrates that the binding process of the antimicrobial HSP1-NH2 peptide depends on the membrane composition and peptide concentration.
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Influence of spin glass-like magnetic relaxation on the zero-field-cooled exchange bias effect
(2018) Bufaiçal, Leandro Felix de Sousa; Bittar, Eduardo Matzenbacher; Garcia, Flávio; Bufaiçal, Leandro Felix de Sousa
The zero-field-cooled exchange bias (ZEB) effect is a remarkable phenomenon recently reported for some reentrant spin glass-like compounds. In this work, the time evolution of magnetization is thoroughly investigated for two ZEB materials in order to figure out the role played by the spin glass-like phase on such effect. La1.5Sr0.5CoMnO6 and La1.5Ca0.5CoMnO6 were chosen as representative samples of ZEB systems, since the former compound presents the largest ZEB reported so far, while the second has a much smaller effect, despite being structurally/chemically similar. Comprehensive magnetic measurements were carried on both samples, and the results are discussed in terms of the amount and time evolution of the spin glass-like phase under the influence of a varying field. We also propose a phenomenological model, based on the pinning of spin glass-like moments and on the dynamics of their magnetic relaxation, to explain the asymmetry observed in the hysteresis loops. The good agreement between the simulated and experimental results confirms our hypothesis that the spin glass-like phase is key to the ZEB effect.