Nucleic Acids Research, Vol 24, Issue 5 859-867, Copyright © 1996 by Oxford University Press
LF Hansen, LK Jensen and JP Jacobsen
One- and two-dimensional 1H NMR spectroscopy were used to characterize the
binding of a homodimeric thiazole orange dye, 1,1'-(4,4,8,8-
tetramethyl-4,8-diazaundecamethylene)-bis-4-(3 -methyl-2,3-dihydro- (benzo-
1,3-thiazole)-2-methylidene)-quinolinium tetraiodide (TOTO), to various
double-stranded DNA oligonucleotides containing symmetric (5'-
pyr-pyr-pu-pu-3')2 or (5'-pu-pu-pyr-pyr-3')2 sequences. It was found that
TOTO binds preferentially to oligonucleotides containing a (5'- CTAG-3')2
or a (5'-CCGG-3')2 sequence. Binding to the (5'-CCGG-3')2 sequence is less
favored than to the (5'-CTAG-3')2 sequence. The complexes of TOTO with
d(CGCTAGCGCTAGCG)2 (10) and d(CGCTAGCCGGCG):d(CGCCGGCTAGCG) (11)
oligonucleotides, each containing two preferential binding sites, was also
examined. In both cases TOTO forms mixtures of 1:1 and 1:2 dsDNA-TOTO
complexes in ratios dependent on the relative amount of TOTO and the
oligonucleotides in the sample. Binding of TOTO to the two oligonucleotides
is sequence selective at the (5'-CTAG-3')2 and (5'-CCGG-3')2 sites. The 1H
NMR spectra of both the 1:2 complexes and the three different 1:1 complexes
have been assigned. A slight negative cooperativity is observed in
formation of the 1:2 complexes. The ratio between the two different 1:1
complexes formed with oligonucleotide 11 is 2.4 in favor of binding to the
(5'- CTAG-3')2 site. This is very similar to results obtained when the two
sites are in different oligonucleotides. Thus the distribution of TOTO
among the (5'-CTAG-3')2 and (5'-CCGG-3')2 sites is independent of whether
the two sites are in the same or two different oligonucleotides.
ARTICLES
Bis-intercalation of a homodimeric thiazole orange dye in DNA in symmetrical pyrimidine-pyrimidine-purine-purine oligonucleotides
Department of Chemistry, Odense University, Denmark.
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