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Journal of Lipid Research, Vol. 46, 245-251, February 2005
Copyright © 2005 by American Society for Biochemistry and Molecular Biology

Fatty acid flip-flop and proton transport determined by short-circuit current in planar bilayers

Kellen Brunaldi, Manoel Arcisio Miranda, Fernando Abdulkader, Rui Curi and Joaquim Procopio¹

Department of Physiology and Biophysics, Biomedical Sciences Institute, University of São Paulo, São Paulo, Brazil 05435040

¹ To whom correspondence should be addressed. e-mail: procopio{at}icb.usp.br

in re-

The effect of palmitic acid (PA) and oleic acid (OA) on electrical parameters of planar membranes was studied. We found a substantial difference between the effects of PA and OA on proton transfer. PA induced a small increase in conductance, requiring a new technique for estimating proton-mediated currents across low-conductance planar bilayers in which an electrometer is used to measure the transmembrane current under virtual short circuit (SCC). Open-circuit voltage and SCC were used to determine proton and leak conductances. OA caused a marked increase in membrane conductance, allowing the use of a voltage-clamp technique.

From SCC data, we were able to estimate the flip-flop rate constants for palmitate (1 x 10^–6 s^–1) and oleate (49 x 10^–6 s^–1) anions. Cholesterol, included in the membrane-forming solution, decreased importantly the leak conductance both in membranes unmodified by FA and in membranes modified by PA added to the bath.

Supplementary key words lipid membranes • cholesterol • electrometer

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