O efeito da composição lipídica da membrana no estudo do mecanismo de ação do peptídeo antimicrobiano esculentina 1b (1-18)

• Autor(a) principal: Silva, Isabela Moreira [UNIFESP]
• Data de Publicação: 2019
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da UNIFESP
• dARK ID: ark:/48912/00130000133qd
• Texto Completo: https://sucupira.capes.gov.br/sucupira/public/consultas/coleta/trabalhoConclusao/viewTrabalhoConclusao.jsf?popup=true&id_trabalho=7778871; https://repositorio.unifesp.br/handle/11600/59620
• topic: Antimicrobial Peptide; Membrane; Electronic Paramagnetic Resonance; Calorimetry; Fluorescence; Peptídeo Antimicrobiano; Membrana; Ressonância Paramagnética Eletrônica; Calorimetria; Fluorescência

The antimicrobial peptides are part of innate immune system of several organisms. They are characterized by the presence of cationic and hydrophobic amino acids that assists in the interaction with plasma membranes. Esculentin 1b (1-18) is an antimicrobial peptide containing 46 amino acids, whose region composed of the first 18 amino acids residues presents bactericidal activity as the whole peptide, without hemolytic activity. The mode of action of antimicrobial peptide Esc 1b (1-18) was studied using mimetic membranes composed of zwitterionic and anionic phospholipids in different physical states. Measurements of carboxyfluorescein leakage, isothermal titration calorimetry and interaction measures using Lagmuir monolayers were made to verify the effect of the peptide on model membranes. To observe the influence of Esc 1b (1-18) in the bilayer, measurements of differential scanning calorimetry and electron paramagnetic resonance were made, and the effect of aggregation caused by the peptide in the membranes was verified using measures of static and dynamic light scattering and Zeta potential. Measurements of circular dichroism and polarization modulation infrared reflection-absorption spectroscopy were made to determine the secondary structure of Esc 1b (1-18) in the presence of vesicles and monolayers, respectively. In general, the results of carboxyfluorescein leakage, isothermal titration calorimetry and maximum insertion pressure show that the peptide interacts mainly with negatively charged and fluid state membranes. Furthermore, it was observed that Esc 1b (1-18) causes a larger influence in the phase transition on DPPG membranes and the peptide inserts deeply on negatively charged membranes. Lastly, it was observed that the peptide presents α-helical secondary structure in the presence of charged membranes. Therefore, the antimicrobial peptide Esculentin 1b (1-18) interacts selectively with negatively charged membranes.