Chemistry Reference
In-Depth Information
LUMO
(+n)
∆
E
(N:
-
)
HOMO
(-n)
E
(N-Hg
II
)
∆
O
Stabilization by
N-Hg
II
bonding
N
N
∆
E
(N-H)
O
Stabilization by
N-H bonding
HOMO
(-n)
O
O
O
NHg
II
NHg
II
NH
N
N
N
O
O
O
HOMO
(-n)
Figure 16.6
Theoretical explanation for the
15
N chemical shifts
(
)
<∆
∆−
E
NHg
II
E
(
NH
−
)
(16.7)
This would be probably caused by a smaller binding energy for Hg
II
to N3 than the
proton-N3 binding energy (Figure 16.6). Interestingly, this interpretation is consist-
ent with a reversible Hg
II
-DNA interaction, since the activation energy (the energy
for the Hg
II
-N3 dissociation in this case) must be small enough for reversible
transitions.
16.6 Applications of the T - H g
II
- T Base Pair
Since the T - Hg
II
-T base pair is a rather irregular base pair with extraordinary stabil-
ity and Hg
II
specifi city, it can be applied to biochemical tools or in devices for nan-
otechnology.
92 - 99
For example, the T-Hg
II
-T base pair can be used as a nanowire
made of a DNA molecule with T-Hg
II
-T base pairs. Indeed, short DNA duplexes
have been made of only T-Hg
II
- T base pairs.
81
Since DNA itself is a weak conductor,
a metallated DNA duplex might be a good conductor. To shed light on this issue,
Joseph and Schuster examined the hole-transport activity of a DNA molecule with
T - Hg
II
- T base pairs.
92
From their studies, it was determined that a DNA molecule
with T - Hg
II
-T base pairs is also a hole transporter with similar activity to that of
normal DNA molecules. However, it is also true that a DNA molecule with T-Hg
II
- T
base pairs is not as good a hole transporter. Theoretical calculations (DFT calcula-
tions) on the charge transfer through the DNA duplex with T-Hg
II
- T base pairs were
performed by Voityuk, in 2006.
93
From his data, no obvious Hg
II
- Hg
II
interaction
was found within HOMO or HOMO-n. Interestingly, this calculation result is con-
sistent with the experimental data of Joseph and Schuste.
92
It was, however, found
that an Hg
II
- Hg
II
interaction was able to be seen in the LUMO, which suggested
