Chemistry Reference
In-Depth Information
Figure 1.9
Chemical shift versus Zn
2+
/duplex ratio plots for the H8 resonances of 5
′
-G4 (
*
)
and 3
-G5 (
), with the terminal adenine H8 protons (o) for comparison: (A)
d(TATGGTACCATA)
2
; (B) d(TATGGATCCATA)
2
; (C) d(TATGGCCATA)
2
. (J. Vinje, J. A.
Parkinson, P.J. Sadler, T. Brown, E. Sletten, Sequence-selective metalation of double-helical
oligodeoxyribonucleotides with PtII, MnII and ZnII ions.
Chem. Eur. J.
, 2003,
9
, 1620-1630.
Copyright Wiley-VCH Verlag GmbH & Co. KGaA. Reproduced with permission.)
′
was reached. This upper level was observed at
r
= [Zn
2+
]/[duplex]
≈
5, which cor-
responds to a [Zn
2+
]/[G] value of
1.2. Plots of chemical shifts versus
r
exhibit the
same trend as for the Mn
2+
titration data (Figure 1.9 ).
In a recent multinuclear NMR study on Zn
2+
binding to oligonucleotides the
variation in
1
H,
15
N and
31
P chemical shifts was monitored as a function of added
ZnCl
2
.
36
Measurements for three different sequences were carried out: d(GGCGCC)
(III); d(GGTACCGGTACC)
2
(VIII); d(GGTATATATACCGGTATA) (IX). The
chemical shift pattern for sequence III followed closely the line-broadening pattern
determined for Mn
2+
(see above
)
. For sequence VIII large chemical
15
N shift effects
were observed for G
7
-N7 at natural abundance, a clear proof of direct metal binding
to this site.
31
P spectra also show large chemical shifts for the central G
7
residue
indicating that at excess ZnCl
2
concentration the Zn
2+
ions have direct contact
with the G
7
phosphate group and/or that a change in the phosphodiester backbone
conformation has occurred.
36
≈
