Background: This study was conducted to investigate the effects of continuous microwaves (2.45 GHz) of different field intensity on acetylcholinesterase activity and protein conformation in muscle fractions from frog skeletal muscles.
Materials/methods: [corrected] Acetylcholinesterase activity in samples from muscle homogenate fractions exposed for 30 min to microwaves of low (10 mW/cm2) or high (20 mW/cm2) intensity at almost constant temperature (1.8 degrees - 2.0 degrees C) was measured by spectrophotometry for three consecutive days after irradiation and compared with the activity in a sham-exposed fraction. Infrared spectroscopy (between 1400 cm(-1)-1800 cm(-1) was performed on the lyophilised fractions using Bruker IFS 113 v.
Results: A significant decrease in enzyme activity on the day of exposure (by 8.4% and 13.6% at high and low field intensity, respectively) was observed. Forty-eight hours later the decrease in enzyme activity in samples exposed to both high- and low-intensity microwaves was less than that in sham-exposed samples. Infrared spectroscopy data showed the Amide I band to be negligibly affected and the absorption maximum in the Amide II band to be significantly shifted from 1540 cm-' (shamexposed) to 1559 cm(1) (exposed) after irradiation.
Conclusions: Exposure to microwaves results in non-thermal, intensity-dependent, prolonged modification of acetylcholinesterase activity in frog skeletal muscles traced up to 48 hrs after exposure. Infrared spectroscopy data argue for induced conformational changes in the secondary structure of muscle proteins: increased content of beta-structures, random coils, and amorphous structures, which were more expressed at low field intensity.