Microtubules in biological cells as circular waveguides and resonators

The microtubules in the cellular cytoskeleton have a fundamental role in th e living processes of biological cells. They are hollow cylinders which res emble circular waveguides or cylindrical resonators. The cutoff and resonan t frequencies of the transverse magnetic and transverse electric modes of t he microtubule cavities are in the band of soft x-rays. This suggests the p ossibility of interaction of electromagnetic cavity modes with inner electr ons in atoms (e.g., in carbon, nitrogen, and oxygen). Biological cells (e.g ., the yeast cells of spherical shape) may also represent cavity resonators . In this case, the resonant frequencies may be in the infrared region.