Reproduction of bacterial chemotaxis by a non-living self-propelled object.

Taxic behavior as a response to an external stimulus is a fundamental function of living organisms. Some bacteria successfully implement chemotaxis without directly controlling the direction of movement. They periodically alternate between run and tumble, i.

Reduced model of a reaction-diffusion system for the collective motion of camphor boats.

The unidirectional motion of a camphor boat along an annular water channel is observable. When camphor boats are placed in a water channel, both homogeneous and inhomogeneous states occur as collective motions, depending on the number of boats. The inhomogeneous state is a type of congestion, that is, the velocities of the boats change with temporal oscillation, and the shock wave appears along the line of travel of the boats.

Another interpretation of the Goldman-Hodgkin-Katz equation based on Ling's adsorption theory.

According to standard membrane theory, the generation of membrane potential is attributed to transmembrane ion transport. However, there have been a number of reports of membrane behavior in conflict with the membrane theory of cellular potential. Putting aside the membrane theory, we scrutinized the generation mechanism of membrane potential from the view of the long-dismissed adsorption theory of Ling.

Generation of membrane potential beyond the conceptual range of Donnan theory and Goldman-Hodgkin-Katz equation.

Donnan theory and Goldman-Hodgkin-Katz equation (GHK eq.) state that the nonzero membrane potential is generated by the asymmetric ion distribution between two solutions separated by a semipermeable membrane and/or by the continuous ion transport across the semipermeable membrane. However, there have been a number of reports of the membrane potential generation behaviors in conflict with those theories.

Ling's Adsorption Theory as a Mechanism of Membrane Potential Generation Observed in Both Living and Nonliving Systems.

The potential between two electrolytic solutions separated by a membrane impermeable to ions was measured and the generation mechanism of potential measured was investigated. From the physiological point of view, a nonzero membrane potential or action potential cannot be observed across the impermeable membrane. However, a nonzero membrane potential including action potential-like potential was clearly observed.

Potential-dependent adsorption/desorption behavior of perfluorosulfonated ionomer on a gold electrode surface studied by cyclic voltammetry, electrochemical quartz microbalance, and electrochemical atomic force microscopy.

Potential-dependent adsorption/desorption behavior of perfluorosulfonated ionomer (PFSI) on a gold electrode was investigated by cyclic voltammetry (CV), electrochemical quartz crystal microbalance (EQCM), and electrochemical atomic force microscopy (EC-AFM) in a Nafion (i.e., PFSI) dispersed aqueous solution without any other electrolyte.