It was reported that the a-helix of protein molecules could be destroyed when they were exposed to the electromagnetic field(EMF) and finally the signal transduction could be affected.To study this effect,one signal molecule,insulin,was exposed to electromagnetic fields at different combinations of the field strength,repetition rate and exposure time.For the first time,structural biology approach was used to detect the EMF effect.The results of a series of measurements on the interaction of electromagnetic fields with insulin in vitro are described.Under our experimental conditions,no effects of electromagnetic field exposure were observed on the molecular conformation.