UCLA

The “Artificial Axon” (AA) is a synthetic excitable system developed in the Zocchi lab, constructedwith the minimal biological components. Based on traditional black lipid membrane setups, the AA is the first cell-free platform capable of producing action potentials (APs) in time. This dissertation details the results of my work with the AA, using the voltage gated potassium channel KvAP as the active ingredient. First, I report on experimental measurements with the AA near the threshold for firing APs, a critical point of the system. In particular, a delay in firing occurs due to the presence of a saddle node bifurcation, and a scaling exponent for this delay is measured. Supplemented by numerical results, I show that this behavior near the critical point has correspondence to the real neuron, due to the universal nature of the dynamics near a critical point. Next, I will characterize the AA in terms of its phenomenology. Using a minimal 3D model based on the Hodgkin-Huxley model, I construct a qualitative phase diagram in the parameter space of the system. The existence of limit cycle regions in this phase diagram indicates that the AA is capable of generating self sustaining AP trains with just a single ion channel. The analysis also shows that the AA, having just one channel species with inactivation, possesses all the same dynamics as a two ion species system without inactivation, such as the Morris-Lecar model for the muscle fiber of the giant barnacle. This result is followed by measurements of the effective inactivation and recovery rates for our minimal model, qualitatively placing the AA with KvAP on the phase diagram. Finally, I will present work on an experimental system consisting of two AA connected by electronic “synapses”, and explore the feasibility of constructing an autonomous oscillator with such a configuration. The connection of two AAs serves as a first step for our long term goal of AA based networks. The dissertation concludes with a short discussion on future directions for the Artificial Axon system.