Response to alternating electric fields of tubulin dimers and microtubule ensembles in electrolytic solutions

Microtubules (MTs), which are cylindrical protein filaments that play crucial roles in eukaryotic cell functions, have been implicated in electrical signalling as biological nanowires. We report on the small-signal AC (\u201calternating current\u201d) conductance of electrolytic solutions containing MTs and tubulin dimers, using a microelectrode system. We find that MTs (212\u2009nM tubulin) in a 20-fold diluted BRB80 electrolyte increase solution conductance by 23% at 100\u2009kHz, and this effect is directly proportional to the concentration of MTs in solution. The frequency response of MT-containing electrolytes exhibits a concentration-independent peak in the conductance spectrum at 111\u2009kHz (503\u2009kHz FWHM that decreases linearly with MT concentration), which appears to be an intrinsic property of MT ensembles in aqueous environments. Conversely, tubulin dimers (42\u2009nM) decrease solution conductance by 5% at 100\u2009kHz under similar conditions. We attribute these effects primarily to changes in the mobility of ionic species due to counter-ion condensation effects, and changes in the solvent structure and solvation dynamics. These results provide insight into MTs\u2019 ability to modulate the conductance of aqueous electrolytes, which in turn, has significant implications for biological information processing, especially in neurons, and for intracellular electrical communication in general.Peer reviewed: YesNRC publication: Ye