Quantifying Ion Transport and Electrochemical Gradients in Synthetic Cell Membranes
Department of Chemical Engineering
Ben-Gurion University of the Negev, Israel
**Lecture will be given in English**
Abstract:
Living cells rely on the controlled movement of ions across their membranes to produce and store energy. In cellular membranes, ion fluxes generate electrochemical potential gradients that power essential processes such as ATP synthesis, nutrient uptake, and membrane potential maintenance. Reproducing these fundamental functions in synthetic membrane systems such as giant unilamellar vesicles (GUVs), micron-sized liposomes, is an important goal toward achieving artificial cells with life-like functionalities. However, achieving this objective remains challenging due to the lack of quantitative, single-compartment methods to measure ion fluxes and electrochemical gradient formation in such synthetic cell-like systems. Here, we present a fluorescence-based approach for quantifying ion fluxes and the resulting changes in electrochemical potential gradients across the membranes of individual GUVs. To achieve precise control over vesicle size and membrane composition, we developed an integrated microfluidic platform enabling high-throughput production and purification of monodisperse GUVs. By combining this platform with quantitative fluorescence analysis, we determined the permeation rates of two biologically important ions – protons (H⁺) and potassium (K⁺) – and directly correlated their fluxes with electrochemical gradient accumulation across the lipid bilayer of single vesicles. Using the same analytical framework, we quantified the ion selectivity of two archetypal ion channels, gramicidin A and outer membrane porin F (OmpF), by measuring the permeation rates of H⁺ and K⁺. We found that proton translocation through gramicidin A is four orders of magnitude faster than potassium transport, whereas OmpF exhibits comparable permeation rates for both ions. We expect that this quantitative approach can inform the design of GUV-based synthetic cells with more complex transport features and provide a versatile platform for exploring ion transport processes relevant to living cells.
