(65m) Understanding Electrochemical Dynamics Near Biological Membrane Interfaces

Electrochemical phenomena are observed in diverse biological processes such as neuronal signaling, cardiac electrophysiology, and ATP synthesis. Classical approaches are based on simplified equivalent-circuit models, which overlook intricate coupling of electrochemical interactions at the microscopic level. With advancements in electrophysiological and microscopic techniques enabling enhanced spatiotemporal resolution, theoretical models capable of interpreting nanoscale data and guiding experimental strategies are required. The overarching goal of my research is to understand the electrochemical dynamics of soft and living systems, which can fill this gap.

In this talk, I will present our recent works that seek to understand the electrochemical response of biological membranes to spatially localized ionic currents, such as those through ion channels or transporters. By combining analytical theory and computer simulations, we show that transmembrane ionic fluxes induce transient long-range electric fields that exhibit power-law decays in unbounded electrolyte solutions. Our results reveal that the electric fields drive propagation of electrochemical signals with remarkably fast speeds (~40 m/s under physiological conditions) along the membrane, which cannot be achieved by bare diffusion. We also investigate the effects of confining the membrane between electrodes applying external electric potential, mimicking a membrane patch-clamp experiment setup. We show that the characteristic power-law decays remain near the pore, but the electrodes modulate ionic dynamics significantly by screening the electrostatic effects at large distances from the pore. Our analysis indicates that the resulting ion dynamics resemble classical poor-conductor models, providing an intuitive perspective on the electrochemical behaviors. Overall, our works not only provide a bridge between electrochemical transport theory and advanced experimental approaches but also open exciting avenues for exploring multi-channel cooperation, electrokinetic flows, membrane electromechanics, and electrophoresis of charged biomolecules in biological systems.