Estudos dos efeitos de carga e da hidrofobicidade na interação de peptídeos antimicrobianos e membranas modelo
Arquivos
Data
2010-08-24
Autores
Costa, Laiana Cristina da [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
Mastoparanos são uma família de peptídeos líticos, extraídos do saco de veneno de vespas sociais, que apresentam moderada a intensa atividade antimicrobiana e alguns são hemolíticos e citotóxicos. Embora o mecanismo de ação destes peptídeos não seja bem compreendido ainda, aceita-se que envolva desestabilização da fase lipídica da membrana celular. Acredita-se que a carga líquida do peptídeo e sua hidrofobicidade média contribuam na modulação da atividade lítica e na seletividade. Nesta dissertação apresentamos um estudo de quatro peptídeos mastoparanos que possuem resíduos ácidos e básicos resultando em uma carga elétrica líquida variando de +1 a +4. Este estudo envolve a análise conformacional destes peptídeos em vesículas zwitteriônicas e aniônicas por dicroísmo circular. Suas atividades líticas foram avaliadas usando espectroscopia de fluorescência monitorando a recuperação da intensidade de fluorescência devido à liberação de marcador fluorescente encapsulado em vesículas. As constantes de partição destes peptídeos em vesículas zwitteriônicas foram também determinadas por espectroscopia de fluorescência usando um método de análise que é independente de modelo. Com o objetivo de entender a influência de resíduos ácidos e a carga líquida dos peptídeos e sua hidrofobicidade na interação peptídeo-lipídio, foram estimadas as contribuições energéticas eletrostáticas e não eletrostática. Para alcançar este objetivo, os resultados obtidos nas isotermas de ligação por fluorescência foram associados com medidas de potencial zeta. Foi observado que a afinidade destes peptídeos em vesículas zwitteriônicas decresce com a carga líquida do peptídeo e as curvas de dose-resposta são mais cooperativas para os dois peptídeos com as cargas mais baixas. Os peptídeos com maior carga apresentaram uma maior afinidade...
Mastoparans are a family of lytic peptides extracted from the venom sac of wasps which present moderate to intense antimicrobial activity and some of them are hemolytic and cytotoxic. Although the mechanism of action of these peptides are still not completely understood, it is accepted that it involves the destabilization of the lipidic phase of the cell membrane. It is believed that both the peptide net electrical charge and its mean hydrophobicity contribute to modulate their lytic activity and selectivity. In this dissertation we present a study of four mastoparan peptides which have acidic and basic residues resulting in net electrical charges ranging from +1 to +4. This study involves the conformational analysis of these peptides in zwitterionic and anionic lipid vesicles by circular dichroism. Their lytic activities were evaluated using fluorescence spectroscopy by the release of fluorescent dye entrapped in these two types of vesicles. The partition constants of these peptides to zwitterionic vesicles were also determined by fluorescence spectroscopy using a method of analysis which is model independent. Aiming to understand the influence of acidic residues and of the peptides net charge and hydrophobocity on the peptide-lipid interaction, the electrostatic and non electrostatic energetic contributions were estimated. To achieve this goal it was used the association of the results of fluorescence binding isotherms and zeta potential measurements. It was observed that the affinity and lytic activity of these peptides in zwitterionic vesicles decrease with the peptides net electrical charges and the dose-response curves are more cooperative for the two peptides with lower net charges. The more charged peptides exhibit higher affinity and lytic activity in anionic vesicles. The most charged peptide displayed the higher selectivity for the vesicles studied. The present work... (Complete abstract click electronic access below)
Mastoparans are a family of lytic peptides extracted from the venom sac of wasps which present moderate to intense antimicrobial activity and some of them are hemolytic and cytotoxic. Although the mechanism of action of these peptides are still not completely understood, it is accepted that it involves the destabilization of the lipidic phase of the cell membrane. It is believed that both the peptide net electrical charge and its mean hydrophobicity contribute to modulate their lytic activity and selectivity. In this dissertation we present a study of four mastoparan peptides which have acidic and basic residues resulting in net electrical charges ranging from +1 to +4. This study involves the conformational analysis of these peptides in zwitterionic and anionic lipid vesicles by circular dichroism. Their lytic activities were evaluated using fluorescence spectroscopy by the release of fluorescent dye entrapped in these two types of vesicles. The partition constants of these peptides to zwitterionic vesicles were also determined by fluorescence spectroscopy using a method of analysis which is model independent. Aiming to understand the influence of acidic residues and of the peptides net charge and hydrophobocity on the peptide-lipid interaction, the electrostatic and non electrostatic energetic contributions were estimated. To achieve this goal it was used the association of the results of fluorescence binding isotherms and zeta potential measurements. It was observed that the affinity and lytic activity of these peptides in zwitterionic vesicles decrease with the peptides net electrical charges and the dose-response curves are more cooperative for the two peptides with lower net charges. The more charged peptides exhibit higher affinity and lytic activity in anionic vesicles. The most charged peptide displayed the higher selectivity for the vesicles studied. The present work... (Complete abstract click electronic access below)
Descrição
Palavras-chave
Biofísica, Biologia molecular, Biofísica molecular, Molecular biophysics
Como citar
COSTA, Laiana Cristina da. Estudos dos efeitos de carga e da hidrofobicidade na interação de peptídeos antimicrobianos e membranas modelo. 2010. 60 f. Dissertação (mestrado) - Universidade Estadual Paulista, Instituto de Biociências, Letras e Ciências Exatas, 2010.