A novel method for the study of fluorescent probes in biological material during exposure to microwave radiation

Instrumentation has been developed which allows the monitoring of fluorescence in erythrocyte ghost membranes before, during, and after exposure to microwave radiation. Using non-fluorescent, UV-transmitting fiber optic cables, excitation light of specific wavelengths was delivered to a stirred sample undergoing irradiation (2450 MHz, CW) within a fluid-filled, temperature-controlled waveguide. Fluorescence was collected using an identical cable and transferred through appropriate filters to standard detecting, amplification and recording devices. We have used the fluorescent probe, 1-anilino-8-naphthalene sulfonate (ANS) to monitor the effect of microwave radiation on the binding of calcium to erythrocyte ghosts. Microwave radiation at specific absorption rates of 10 and 200 mW/g had no effect on the binding of ANS to the membranes. Dose-response curves also showed no influence of microwaves on calcium binding between 2.0 and 10.0 x 10(-4) M. In addition, experiments studying fluorescence energy transfer between intrinsic tryptophan residues and membrane bound ANS showed that intermolecular distances between donor and acceptor are also unaffected by microwave radiation. We have thus shown that 2450 MHz microwave radiation at the specific absorption rates used does not interfere with the binding of calcium to erythrocyte ghosts or alter intermolecular distances between intrinsic molecules and bound ANS.