Electronic states of natural and metal-ion doped DNA

Electronic states of pristine and metal ion doped salmon DNA’s are studied with EPR and SQUID. Intrinsically no EPR signal is observed in purified salmon DNA, consistent with a semiconducting nature of the pristine DNA, but inconsistent with a metal or a superconductor as reported previously. Although we obtained successfully the divalent metal ion-DNA complexes with one-dimensional array of ions located in between the bases of a base pair, substantial EPR signal except for the case of 3d transition metal ions is not observed. This leads to the conclusion that divalent metal ions counterbalances two phosphate anions instead of Na counter ions in B-DNA, which contradicts the metallic behavior reported previously (A. Rakitin, et al., PRL 86, 3670 (2001)). A comment will also be given on the recent report: “Intrinsic Low Temperature Paramagnetism in B-DNA” (S. Nakamae et al., PRL 94, 248102 (2005)).