Chain‐length‐dependent microwave absorption of DNA

Biological effects of low-level (producing nonsignificant thermal induction) microwave or radiofrequency radiation have been extensively r e p ~r t e d .l -~ Such low-level biological responses are suggestive of molecular or membrane interactions leading to disruption of function.This is particularly true for reported genetic effects including effects on spermat~genesis.~Chromosomal and genetic effects have been reviewed by Leach.6Although there has been no definitive theoretical work suggesting a linkage between molecular absorption of microwave energy, disruption of function, and reported genetic effects, calculations have been made which indicate that the DNA molecule may show strong resonant absorption a t microwave f r e q u e n c i e ~. ~, ~ These calculations considered longitudinal and transverse vibrational modes (acoustic or optical) in dehydrated double-stranded DNA of varying base pair numbers.The resonant modes were base-pair-number or chain-length-dependent, with the longitudinal acoustic vibrational modes being the most likely in the microwave frequency range.Van Zandt et al.9 recently extended this work to consider critically damped absorption of DNA in aqueous solutions.We previously reported microwave absorption of aqueous solution of DNA in the 8-12 GHz frequency rangelo using an optical heterodyne technique for detection.11J2Our work was in good agreement with the theoretical work of Van Zandt et aL9 Now we have extended this work using dielectrometric methods, first investigating commercially produced E. coli DNA13 and then highly purified ma-