DNA is an interesting material from the viewpoint of the materials science. This paper discusses the electronic
states of the metal incorporated M-DNA complexes with several species of metal ions. M-DNA prepared by the
ordinary methanol precipitation technique has been investigated with ESR, STM and optical absorption, and
concluded that the metal ion hydrated with several water molecules locates in between the bases of a base pair
and that the divalent metal ions are incorporated into DNA in place of two Na cations as the counter ion for PO<sup>-</sup><sub>4</sub>in the DNA backbones. Only in Fe-DNA, it was confirmed that the Fe2+ in the FeCl<sub>2</sub> aqueous solution reacts
with DNA to form Fe-DNA complex with Fe<sup>3+</sup>, where the charge would transfer to DNA. Within 30 min, the
hydrolysis of Fe<sup>2+</sup> to form Fe<sup>3+</sup>O(OH) did not occur in the FeCl<sub>2</sub> aqueous solution at room temperature. The
optical absorption spectra of Fe-DNA is similar to that for FeCl<sub>3</sub> with the ionic character, but definitely differs
from that of Fe<sup>3+</sup>O(OH) with the covalent bonding nature, suggesting the ionic character of Fe<sup>3+</sup> in Fe-DNA.
Finally, the possible two kinds of electronic states for Zn-DNA with different bonding nature will be discussed
in relation to the recent report on Zn-DNA.
DNA has attracted much interest as a material for nano science and technology. To unveil the intrinsic nature of
DNA both in natural form and modified forms of M-DNA with a variety of divalent metal ions. From the magnetic
and optical properties, it is concluded that the electronic states of natural salmon DNA is of semiconducting.
Thus, only the hopping transport via excited states or impurity site like oxygens is expected. One of the efforts
to introduce charge carriers into DNA, insertion of divalent metal ions, has been studied from magnetic, optical
and structural aspects. It was concluded that the divalent metal ions are inserted in between the bases of a base
pair, in place of hydrogen bonds, and the charge transfer from the metal ions to DNA occurs only in the case of
DNA has attracted much interest as a material for nano science and technology. We have studied DNA both
in natural forms and modified forms M-DNA by insertion of a variety of metal ions. On the ground of basic
science, we tried to unveil the intrinsic physical properties, especially magnetic properties of natural DNA and a
possibility of charge carrier doping by the metal ion insertion. Diamagnetic nature of natural DNA and a variety
of features in M-DNA will be presented.