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Doctoral Thesis
DOI
10.11606/T.42.2007.tde-19102007-092737
Document
Author
Full name
Manoel de Arcisio Miranda Filho
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2007
Supervisor
Committee
Araujo Filho, Joaquim Procopio de (President)
Martins, Anna Karenina Azevedo
Nouailhetas, Viviane Louise Andree
Silveira, Leonardo dos Reis
Souza, Maria Oliveira de
Title in Portuguese
Efeitos elétricos de ácidos graxos livres em bicamadas lipídicas planas.
Keywords in Portuguese
Ácidos graxos
Bicamada lipídica
Condutância
Medidas elétricas
Permeabilidade
Protón
Abstract in Portuguese
Ácidos graxos livres (FFA) são importantes mediadores do transporte de prótons através de membranas. Porém, pouco se sabe sobre a influência estrutural tanto dos FFA como do ambiente lipídico na translocação de prótons através de membranas. Tanto os efeitos do comprimento da cadeia e número de insaturações dos FFA como a composição da membrana foram analisados por medidas elétricas em bicamadas lipídicas planas. Condutância a prótons (GH+) e condutância de vazamento (Gleak) foram calculadas a partir de medidas de voltagem em circuito aberto e de corrente de curto-circuito obtidas através de um eletrômetro ou um amplificador de patch-clamp (modo de voltage-clamp). Nossos resultados mostram que FFA com cis-insaturações causam um efeito mais pronunciado no transporte de próton quando comparados com FFA saturados ou trans-insaturação. Colesterol e cardiolipina diminuem Gleak de membranas. Cardiolipina também diminui GH+. Esses efeitos indicam uma dupla modulação do transporte de prótons: pelo mecanismo de flip-flop dos FFA e por uma via difusional simples adicional.
Title in English
Electrical effects of free fatty acids in planar lipid bilayers.
Keywords in English
Conductance
Eletrical measurements
Fatty acids
Lipid bilayer
Permeability
Proton
Abstract in English
Free fatty acids (FFA) are important mediatiors of proton transport across membranes. However, little is known about the structural influence of both FFA and the membrane environment have in proton translocation across phospholipid membranes and by which means this influence is brought about. Both the effects of FFA chain length and insaturation and membrane composition on proton transport have been addressed in this study by electrical measurements in planar lipid bilayers. Proton conductance (GH+) and leak conductance (Gleak) were calculated from open-circuit voltage and short-circuit current measurements obtained using either an electrometer or a patch-clamp amplifier (voltage-clamp mode). We found that cis-unsaturated FFA caused a more pronounced effect on proton transport as compared to saturated or trans-unsaturated FFA. Cholesterol and cardiolipin decreased Gleak. Cardiolipin also decreased GH+. These effects indicate a dual modulation of protein-independent proton transport by FFA through flip-flop and by an additional simple diffusional pathway.
 
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Publishing Date
2007-10-23
 
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