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Weak Acid Permeation in Synthetic Lipid Vesicles and Across the Yeast Plasma Membrane.

Biophysical journal (2019-12-18)
Matteo Gabba, Jacopo Frallicciardi, Joury van 't Klooster, Ryan Henderson, Łukasz Syga, Robert Mans, Antonius J A van Maris, Bert Poolman
ABSTRACT

We present a fluorescence-based approach for determination of the permeability of small molecules across the membranes of lipid vesicles and living cells. With properly designed experiments, the method allows us to assess the membrane physical properties both in vitro and in vivo. We find that the permeability of weak acids increases in the order of benzoic > acetic > formic > lactic, both in synthetic lipid vesicles and the plasma membrane of Saccharomyces cerevisiae, but the permeability is much lower in yeast (one to two orders of magnitude). We observe a relation between the molecule permeability and the saturation of the lipid acyl chain (i.e., lipid packing) in the synthetic lipid vesicles. By analyzing wild-type yeast and a manifold knockout strain lacking all putative lactic acid transporters, we conclude that the yeast plasma membrane is impermeable to lactic acid on timescales up to ∼2.5 h.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Sodium L-lactate, ≥99.0% (NT)
Sigma-Aldrich
Calcein, Used for the fluorometric determination of calcium and EDTA titration of calcium in the presence of magnesium.
Sigma-Aldrich
8-Hydroxypyrene-1,3,6-trisulfonic acid trisodium salt, ≥96%
Sigma-Aldrich
Sodium benzoate, BioXtra, ≥99.5%
Sigma-Aldrich
1,2-Dipalmitoyl-sn-glycero-3-phosphoethanolamine, ≥97%
CellCrown inserts, 6 well plate inserts with 1.0 μm polycarbonate filter, sterile