Fatty acid flip-flop and proton transport determined by short-circuit current in planar bilayers.
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.
Brunaldi
Kellen
K
Department of Physiology and Biophysics, Biomedical Sciences Institute, University of São Paulo, São Paulo, Brazil 05435040.
Miranda
Manoel Arcisio
MA
Abdulkader
Fernando
F
Curi
Rui
R
Procopio
Joaquim
J
D001669:Biochemical Phenomena; D001671:Biochemistry; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism; D004566:Electrodes; D004594:Electrophysiology; D005227:Fatty Acids / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism*; D046911:Macromolecular Substances / Q000378:metabolism; D019301:Oleic Acid / Q000737:chemistry / Q000378:metabolism; D009829:Oleic Acids / Q000494:pharmacology; D019308:Palmitic Acid / Q000737:chemistry; D010169:Palmitic Acids / Q000494:pharmacology; D010743:Phospholipids / Q000737:chemistry; D011522:Protons; D013025:Glycine max / Q000378:metabolism
D005227:Fatty Acids; D008051:Lipid Bilayers; D046911:Macromolecular Substances; D009829:Oleic Acids; D010169:Palmitic Acids; D010743:Phospholipids; D011522:Protons; D019301:Oleic Acid; D019308:Palmitic Acid; D002784:Cholesterol