Complex microwave conductivity of Na-DNA powders

We report the complex microwave conductivity, sigma = sigma(1) - i sigma(2), of Na-DNA powders, which was measured from 80 to 300 K by using a microwave cavity perturbation technique. We found that the magnitude of sigma(1) near room temperature was much larger than the contribution of the surrounding water molecules, and that the decrease of sigma(1) with decreasing temperature was sufficiently stronger than that of the conduction of counterions. These results clearly suggest that the electrical conduction of Na-DNA is intrinsically semiconductive.