Chemistry Reference
In-Depth Information
a
b
4
G4 H8
10
G3 H8
G4 H8
8
3
6
G5 H8
2
A5 H8
4
1
G2 H8
2
G12 H8
G10 H8
A11 H2
0
0
0
5
10
15 20
r*10
4
25
30
0
5
10
15 20
r*10
4
25
30
Figure 1.8
Plot of
T
1
−
1
versus
r
= [Ni(II)]/[Phosphate] at 312 K for G-H8 and A-H8 resonances
of selected residues along the sequences: (a) [d(C
1
G
2
C
3
G
4
A
5
A
6
T
7
T
8
C
9
G
10
C
11
G
12
)]
2
; (b) [d(A
1
T
2
G
3
G
4
G
5
T
6
A
7
C
8
C
9
C
10
A
11
T
12
)]
2
. (Reprinted from
Inorg. Chim. Acta
,
273
, 1-2, E. Moldrheim,
B. Andersen, N. A. Froystein, E. Sletten, Interaction of manganese (II), cobalt (II) and nickel
(II) with DNA oligomers studied by 1H NMR spectroscopy, 6. Copyright 1998, with permis-
sion from Elsevier.)
to stabilize the double-helical structure, Cu
2+
salts were shown to induce a dramatic
lowering of the melting temperature (Figure 1.1). Recent NMR studies of Cu
2+
and
Cu en
(
)
2
+
binding to the Dickerson-Drew duplex show the same selectivity pattern
as for the other transition metals.
47
The increase in line width at an
r
= [Cu
2+
]/
[Phosphate] of 2.5
2
10
− 3
was approximately 10 Hz, a corresponding increase in line
width for [Cu(en)
2
]
2+
was obtained at
r
= 15
×
10
− 3
.
Oikawa and Kawanishi have investigated the telomere shortening induced by
H
2
O
2
plus Cu
2+
and found predominant DNA damage at the 5
×
in a 48-base fragment of the telomere duplex.
48
In contrast, when single-stranded
DNA was used, the damage induced by oxidative stress occurred at every guanine.
The difference in site specifi city of DNA damage between double-stranded DNA
and single-stranded DNA could be explained in terms of the lower ionization
potentials of stacked guanine base pairs in double-stranded DNA, on the basis of
theoretical calculations.
′
- site of 5
′
- GGG - 3
′
Zn
2+
Ions
UV spectroscopic titration studies of ctDNA by ZnCl
2
indicate that Zn
2+
ions bind
both to phosphate groups and base nitrogen atoms.
3
Marzilli and coworkers carried
out Zn
2+
titration of duplex d(ATG
3
G
4
G
5
TACCCAT) (VII) containing a GGG
triplet, and found the chemical shift variation for the G-H8 in the order
G
4
G
5
.
49
Zn
2+
titration experiments analogous to those using Mn
2+
(see above) have
been carried out for sequences III, IV and V.
10
In contrast to paramagnetic metal
systems, where very low metal/DNA ratios were employed, excess salt was added
to the duplex solutions until an upper limit of Zn
2+
- induced chemical shift changes
>
G
3
>>
