Chemistry Reference
In-Depth Information
phi
3+
NH
N
HN
phi
Rh
H
N
N
bpy
N
Asp Pro Asp Glu Leu Glu His Ala Ala
Lys His Glu Ala Ala Ala Lys CONH
2
O
HN
NH
N
N
Zn
2+
Figure 12.6
The Rh(III) complex-peptide conjugate, Rh(phi)
2
bpy
′
-Peptide (Rh-P
1
) with the
Zn(II) coordination site being illustrated
lytic activity of the native enzyme.
54
It must be emphasized that both appended
peptides did not contribute to the recognition properties of the sequence-neutral
metallointercalator [Rh(phi)
2
(bpy
′
)]
3+
but effi ciently delivered the metal ion to the
sugar - phosphate backbone.
12.4
A Critical Survey and Future Perspectives
Research on the development of artifi cial nucleases aims at high cleavage effi ciency,
DNA affi nity and sequence selectivity. Attempting to compare different transition
metal complex-peptide conjugates regarding their DNA cleavage effi ciency becomes
a rather diffi cult task due to the large variety of reaction conditions used. Therefore,
comparisons can be made tentatively under the concept that in most cases, reaction
conditions are optimized in order to give the best results. Furthermore, there is no
available data suffi cient for comparisons of kinetic parameters. Experimental data
derived from the studies already described are summarized in Table 12.2.
First of all, DNA binding by intercalation increases DNA binding affi nity by at
least two orders of magnitude compared to DNA groove binding. For example, for
the series [Ru(bpy)
3
]
2+
, [Ru(bpy)
2
(phen)]
2+
, [Ru(bpy)
2
(DIP)]
2+
and [Ru(bpy)
2
(phi)]
2+
,
K
b
values of 0.7
l0
5
M
− 1
, have been determined
respectively.
55
Given that increased DNA binding affi nity results, in most cases,
in high DNA cleavage effi ciency, it is clearly seen from Table 12.2 (cleavage effi -
ciency is compared as % formation of nicked and linear DNA from plasmid DNA
×
l0
3
, 0.7
×
l0
3
, 1.7
×
l0
3
, and 1.6
×
