Excitable artificial cells of proteinoid.

The proteinoid cells are assembled of thermal polymers of amino acids. Typically, an appropriate mixture of amino acids containing aspartic or glutamic acid is heated at 190 degrees C for 6 h, stirred with water for 2 h, dialyzed during 2 d, and lyophilized. Spheroidal cells are made from such polymer by dissolving it in the water by boiling, and then cooling. Many of them can be made by sonication at room temperature. These artificial cells, ranging from microns to tens of microns in diameter (depending on composition and preparation), have double membranes and various internal compositions. The spherules can microencapsulate dyes, oxidant-reductant compounds or acceptor-donor substances, and can be packed together. Such spherules display electrical polarization and electrical discharges and respond to intra- and extracellular ionic and electric influence upon membrane and action potential. These properties arise from the double membrane structure, asymmetric membrane permeability, and channeling phenomena. Such features as exponential dependence of the steady-state conductance and capacitance as well as negative resistance of the membrane seem to be responsible for the flip-flop alternations of the membrane polarization, rhythmic electric oscillations, and all-or-none action potentials. The presence of such chromophores as pteridine and flavin in polymers constituting these cells is responsible for their photosensitivity.