Modelling oscillations of membrane potential difference

The oscillation of the membrane potential difference (PD) is considered in terms of one or more ion transporters changing their conductances. For slow oscillations (period greater than about one minute), the transporters could be identified by employing the currentvoltage (I/V) technique. The electrical characteristics of each transporter population were then modeled and the evolution of the model parameters with time obtained. Examples of single transporter type changing against a steady background conductance were the proton pump in the charophyte Chara australis and a putative potassium pump in Ventricaria ventricosa. A detailed modeling was done for the former, but it is in early development for the latter. The hypertonic regulation in the salt-tolerant charophyte Lamprothamnium spp., and an interaction of the proton pump and the proton channel in C. australis are given as examples of two transporters responding to a change in salinity and membrane PD, respectively. A detailed modeling was done for each response. The hypotonic regulation in Lamprothamnium involves a complex interaction of several transporters, initiated by the decrease of the medium salinity. Finally, spontaneous action potentials (APs) in C. australis are shown as the medium salinity is increased. The examples demonstrate the analytical and predictive power of the I/V methodology coupled with the systems biology modeling.