Coupling of electrodynamic fields to vibrational modes in helical structures

Abstract

Helical structures like alpha helices, DNA, and microtubules have profound importance in biology. It has been suggested that these periodic arrangements of constituent units could support collective excitations similarly to crystalline solids. Here, we examine the interaction between such constructs and oscillating dipoles, and evaluate the role of the helicity in the coupling between electrodynamic fields and vibrations. Based on vibrational and eigenfunction analyses we identify a group of modes of coherent oscillations that give rise to a strong and delocalized response, selectivity in frequency, and a typical interaction range. To describe the field scattering due to the structure vibrations we consider an anisotropic permittivity with a helical periodicity, which applies to all vibration types and close dipole locations. The type of resonances identified here may help explain the role of electrodynamic fields in the diverse functionality of cytoskeletal microtubules in the cellular environment.