ABSTRACT
As confirmed in Chapter 2, natural DNA is a semiconducting
material, and as discussed in Chapter 4, the electrical conduction
of DNA with macroscopic scale is mainly carried out by the proton
conduction of water molecules contained in the double-helical DNA.
One of the attempts to inject electronic charge carriers into DNA
is the insertion of a divalent metal ion between the bases of a
base pair of DNA, as first reported by Lee et al. [16], which is introduced in Section 1.2.2. After that, Rakitin et al. measured the I-V characteristics of Zn-DNA with nanotechnology and found the disappearance of the characteristic feature of semiconducting
materials: the threshold voltage against the current flow, which has
been observed in B-DNA [17]. Thus, they concluded that Zn-DNAwas
a promising candidate for conducting nanowires. Following their
report, many researches on Zn-DNA and other M-DNAs have been
carried out experimentally [19, 24, 25, 27, 28, 46, 93-95, 144, 157,
175, 176, 251-253] and theoretically [21-23]. Does Zn-DNA really
have metallic nature? The valence of Zn ions in Zn-DNA is known
to be 2+, that is, charge transfer from Zn to DNA does not occur. Nanotechnological measurement of electrical conduction [17] is
affected by several factors, which are sometimes difficult to control.
Thus, it is meaningful to study the electronic states of M-DNA by means of other techniques, especially non-contact techniques, such
as optical absorption and magnetic property. On the other hand,
does M-DNA have the same electronic structure even with the samples synthesized by different methods? These points on M-DNA will be described in Section 7.2. In this chapter, UV/Vis absorption
and the magnetic property of M-DNA will be discussed.
