Self-Organizing Proteinoid–Actin Networks: Structure and Voltage Dynamics

Proteinoids are thermal proteins produced by heating amino acids to their melting point and initiation of polymerization to produce polymeric chains. Proteinoids swell in aqueous solution forming hollow microspheres, usually filled with aqueous solution. The microspheres produce spikes of electrical potential similar to the action potentials of living neurons. The cytoskeletal protein actin is known in its filamentous form as F-actin. Filaments are organized in a double helix structure consisting of polymerized globular actin monomers. Actin is a protein that is abundantly expressed in all eukaryotic cells and plays a crucial role in cellular functions by forming an intracellular scaffold, actuators, and pathways for information transfer and processing. We produce and study proteinoid-actin networks as physical models of primitive neurons. We look at their structure and electrical dynamics. We use scanning electron microscopy and multichannel electrical recordings to study microsphere assemblies. They have distinct surface features, including ion channel-like pores. The proteinoid-actin mixture exhibits enhanced electrical properties compared to its individual components. Its conductivity (σ = 4.68 × 10^-4 S/cm) is higher than those of both pure actin (σ = 1.23 × 10^-4 S/cm) and pure proteinoid (σ = 2.45 × 10^-4 S/cm). The increased conductivity and new oscillatory patterns suggest a synergy. They indicate a synergy between the proteinoid and actin components in the mixture. Multichannel analysis reveals type I regular spiking in proteinoid networks (Δ<i>V</i> ≈ 50 mV, τ = 52.4 s), type II excitability in actin (<i>V</i> _max ≈ 40 mV), and bistable dynamics in the mixture. These findings suggest that proteinoid-actin complexes can form primitive bioelectrical systems. This might lead to the better understanding of the evolution of the primordial neural system.