Estudos das interações do peptídeo antimicrobiano Polybia MP1 com membranas modelo: mecanismo de ação e especificidade

• Ano de defesa: 2014
• Autor(a) principal: Slade, Natália Bueno Leite [UNESP]
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Estadual Paulista (Unesp)
• Palavras-chave em Português: Biologia molecular; Biofísica; Peptídeos antobióticos; Dicronísmo circular; Microscopia confocal; Membranas (Biologia)
• Link de acesso: http://hdl.handle.net/11449/127560

Bioactive peptides are of high interest as substitutes of conventional drugs since some of them present antimicrobial, antifungal and/or anticancer action. They are predominantly cationic and it has been shown that their activity is modulated by electrostatic interactions, hydrophobic contributions and the elastic features of the membranes their target. The mastoparan peptide Polybia MP1 (MP1) possesses two acidic residues (D2 and D8) and three basic ones (K4, K5 and K11), which together with the amidation of the C-terminal confers to it a relatively low net charge Q=+2. In this thesis, we analyzed the importance of the MP1 amino acid sequence, charge and hidrophobicity to the interaction with distinct model membranes, since the presence of acidic residues is a rare characteristic among the bioactive peptides and, beyond this, MP1 presents high antimicrobial and anticancer activities without being hemolytic. In search of understand its specificity and mechanism of action for bacteria and cancer cells, the activity and affinity of MP1 was assessed through circular dichroism and fluorescence spectroscopy, electrophoretic and dynamic light scattering measurements, and confocal microscopy. These techniques allowed the observation of the peptide structuration, the peptide partitioning from water to the model membranes interface, the peptide lytic activity, and the liposome aggregation due to peptide addition. From this, it was possible estimate the energetic contributions involved in the system, besides the dimension of the damages caused by MP1 on the membranes surface. MP1 showed that its low net charge and the presence of two acidic residues play an important role in modulating its structuration and activity in a wide range of lipid compositions, by equilibrating electrostatic and non-electrostatic contributions giving basis to understand its action as bioactive...