This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This is a subproposal within one of the core aims of the Biocurrents Research Center. We are currently developing ion-selective electrodes (ISEs) with improved response time (<1ms) and signal-to-noise ratio in order to extract meaningful single ion channel characteristics from global extracellular ionic gradients. These characteristics include mean open time, conductance and channel density. Prior to collecting cellular data and testing the above hypothesis, it is necessary to determine the influence of diffusion processes on ion fluxes at a finite distance from the point of efflux or influx. Therefore, we have set out to model the 3D environment of the boundary layer of the cell and demonstrate whether the ISE can reliably resolve unitary ion currents from clusters of ion channels within the extracellular space.