T. Peleg-shulman et al., Effects of monofunctional platinum binding on the thermal stability and conformation of a self-complementary 22-mer, J INORG BIO, 81(4), 2000, pp. 313-323
We investigated the effect of various monofunctional platinum complexes on
the thermal stability and conformation of a self-complementary 22-mer duple
x oligonucleotide by means of CD and UV melting profiles. We studied severa
l families of triamine complexes of the general formula PtA(2)AmCl where A(
2)=(NH3)(2) and ethylenediamine and where Am=N1-4-methyl-pyridine, N7-guano
sine, and 9-ethyl-guanine. Platination by the N1-4-methyl-pyridine and 9-et
hyl-guanine complexes led to a decrease in the T-m of the oligonucleotide b
y 2-11.5 degreesC while platination with the N7-guanosine complexes led to
a rise in the melting temperature of the oligonucleotides by 4.5 degreesC.
A similar inverse correlation between the two groups of platinum compounds
was found in the CD spectra. In all cases, the cis isomer had a more pronou
nced effect on both the melting curve and the CD spectrum. The cis isomer w
as found to have a more destabilizing effect than its trans counterpart. Th
is indicates that the cis geometry in fact forces a greater structural cons
traint on the backbone of the double helix. We have also found that the sug
ar of the guanosine has a significant influence on both the T-m and CD spec
tra; the sugar moiety contributes to the stability of the double helix, pro
bably through the formation of hydrogen bonds. (C) 2000 Elsevier Science S.
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