Chemistry Reference
In-Depth Information
chelating proteins). Furthermore, in the case of eukaryotic cells, genomic DNA is
surrounded by a nuclear membrane and is shielded from Hg
II
attack. Therefore,
effects of Hg
II
on the genetic mutations might be evident in prokaryotes. In addition,
intrinsic genetic effects of Hg
II
could be studied by using PCR as the simplest model
replication system.
16.8 Concluding Remarks
The structure of the T-Hg
II
-T base pair, once one of the mysteries of Hg
II
- DNA
interaction modes in DNA duplexes, was determined from
15
N NMR spectra. Espe-
cially,
15
N -
15
N
J
- coupling across Hg
II
(
2
J
NN
:
15
N
- Hg
II
-
15
N
) provided defi nite evidence
of the N-Hg
II
- N covalent linkage in the T - Hg
II
-T base pair. Interestingly, its structure
was fully consistent with the structural model proposed by Katz in 1963. It is aston-
ishing that even in the early stages of these studies, the correct structure of the T-
Hg
II
-T base pair was suggested from limited data. It is also interesting to note that
the lower - fi eld shifts of
15
N NMR chemical shifts upon Hg
II
binding are consistent
with the reversibility of the N-Hg
II
bond formation. Therefore, the N-Hg
II
bond
might be classifi ed into a relatively weak category among covalent bonds. However,
T - Hg
II
- T base pairs with N - Hg
II
bonds are suffi ciently stable to form a duplex that
is rather more stable than the Watson-Crick A-T base pair in some sequences. Fur-
thermore, its association/dissociation kinetics are slow relative to an NMR timescale.
Such characteristics of the T-Hg
II
-T base pair would promote irregular DNA struc-
tures. However, little is known about the weak interatomic interactions within the
T - Hg
II
-T base pair and interactions between neighbouring T-Hg
II
- T base pairs. These
residual issues need attention as the next targets in this fi eld.
References
1.
Katz , S. ; The reversible reaction of sodium thymonucleate and mercuric chloride ;
J. Am.
Chem. Soc.
, 1952 ,
74
, 2238 - 2245 .
Thomas , C.A. ; The Interaction of HgCl
2
with Sodium Thymonucleate ;
J. Am. Chem. Soc.
,
1954 ,
76
, 6032 - 6034 .
Dove , W.F. ; Yamane , T.; The complete retention of transforming activity after reversal
of the interaction of DNA with mercuric ion;
Biochem. Biophys. Res. Commun.
, 1960 ,
3
, 608 .
Yamane , T. ; Davidson , N.; On the complexing of desoxyribonucleic acid (DNA) by
mercuric ion;
J. Am. Chem. Soc.
, 1961 ,
83
, 2599 - 2607 .
Yamane , T. ; Davidson , N. ; Note on spectra of mercury(II) and silver(I) complexes of
some polyribonucleotides and ribonucleic acid;
Biochim. Biophys. Acta
, 1962 ,
55
,
780 - 782 .
Katz ,
2.
3.
4.
5.
Hg
II
;
6.
S. ;
Mechanism
of
reaction
of
polynucleotides
and
Nature
,
1962 ,
194
,
569 .
Katz , S. ; Reversible reaction of double -stranded polynucleotides and Hg
II
: Separation
of the strand;
Nature
, 1962 ,
195
, 997 - 998 .
Katz , S. ; Reversible reaction of Hg(II) and double - stranded polynucleotides: A step -
function theory and its signifi cance;
Biochim. Biophys. Acta
, 1963 ,
68
, 240 - 253 .
7.
8.
