The effect of 2450-MHz microwave radiation during microtubular polymerization in vitro.

Exposure to 2450-MHz (cw) microwave radiation causes inhibition of cell division in intact cells and varied in vivo biological effects in both avian and mammalian species. Because these reported effects may result from alterations in the dynamics of microtubule formation, we studied the effects of simultaneous microwave exposure (2450 MHz, cw) during each of the three critical stages of the intracellar polymerization cycle. In addition, using circular dichroism spectroscopy, we studied the effect of microwave irradiation on the secondary structure of purified tubulin polypeptides. These studies were accomplished using specially constructed exposure systems that permit the continuous recording of turbidometric or circular dichroism measurements during simultaneous exposure to microwaves. The baseline turbidity of microtubular protein did not change under the influence of microwave radiation (20 or 200 mW/g SAR) and irradiation had no effect on the light-scattering properties of the depolymerized protein. EGTA-induced polymerization and cold-induced depolymerization patterns were also similar for both control and microwave-irradiated samples. The circular dichroism spectrum of purified tubulin also did not appear to be influenced by microwave irradiation, indicating a lack of effect on the protein secondary structure. The data suggest that the cellular effects of microwaves are not due to changes in microtubular proteins or their rate of polymerization.