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PhD Student, University of Massachusetts Medical School


Cells use plasma membrane proton fluxes to maintain cytoplasmic and extracellular pH and to mediate the co-transport of metabolites and ions. Because proton-coupled transport often involves movement of multiple substrates, traditional electrical measurements provide limited information about proton transport at the cell surface. My research is focused on developing an optical method to visualize proton fluxes at the cell surface through ion channels or transporters. To visualize proton fluxes over the entire landscape of a cell, I covalently attached small molecule fluorescent pH sensors to the cell surface. I found that the extracellularly facing sensors enable real-time detection of proton accumulation and depletion at the plasma membrane, providing an indirect readout of channel and transporter activity that correlated with whole-cell proton current. Moreover, the proton wavefront emanating from one cell was readily visible as it crossed over nearby cells. Given that any small-molecule fluorescent sensor can be covalently attached to the cell surface. The approach I developed is readily adaptable to visualize most electrogenic and non-electrogenic transport events at the plasma membrane.