Measuring and modelling electrostatic and electro-conductive properties of cytoskeletal protein filaments: Physical Force, Energy, Power and Information Considerations
We provide an overview of the modeling performed at both atomistic and coarse-grained levels in order to gain insight into electrostatic and electro-conductive properties of the cytoskeleton. Computer simulations and experimental measurements carried out for microtubules and actin filaments are presented. Charge and dipole values for monomers and dimers as well as polymerized forms of these proteins are summarized. Continuum approximations for cable equations describing actin filaments and microtubules compare favorably to measurements in buffer solutions showing soliton waves and transistor-like amplification of ionic signals. In addition, experimental evidence for memristive behavior of microtubules supports their hypothesized role in memory storage and information processing. Conductivity and capacitance of tubulin and microtubules have been measured and modeled. A dramatic change in conductivity occurs when tubulin forms microtubules. In living cells, this signals a conductive phase transition coinciding with mitosis in dividing cells.
Finally, we provide estimates of the forces, energies and power involved in the action of electric fields on microtubules and kinesin motors. These calculations are compared and contrasted with typical values experienced at a cell level. We will also discuss how cytoskeleton can electromagnetically interact with the cells exterior via its coupling with the ion channels and other membrane proteins.