Nonlinear electric response of the diffuse double layer to an abrupt charge displacement inside a biological membrane.

• Abrupt, intramolecular charge displacement inside a biological membrane. • Electric response of the diffuse double layer. • Primary light-induced electric signals of bacteriorhodopsin. • Bipolar voltage decay as a consequence of capacity change of diffuse double layer. • Possible physiological consequences are discussed. In order to elucidate the old, still unsolved problem of how the diffuse electric double layer responds to an abrupt, intramolecular charge displacement inside a biological membrane, we investigated the fastest components of the light-induced electric signals of bacteriorhodopsin and its mutants, in numerous ionic and buffer solutions. The obtained data for temperature and solute concentration dependence were interpreted as a consequence of changes in the capacity of the diffuse double layer surrounding the purple membrane. The possible physiological consequences of this so far not demonstrated phenomenon are discussed. [ABSTRACT FROM AUTHOR]