title: Bis-intercalation of a homodimeric thiazole orange dye in DNA in symmetrical pyrimidine-pyrimidine-purine-purine oligonucleotides.
abstract: 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.
authors.affiliation: Department of Chemistry, Odense University, Denmark.
authors.forename: L F
authors.initials: LF
authors.lastname: Hansen
authors.forename: L K
authors.initials: LK
authors.lastname: Jensen
authors.forename: J P
authors.initials: JP
authors.lastname: Jacobsen
mesh_terms: D001483:Base Sequence; D052160:Benzothiazoles; D004247:DNA / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry; D008969:Molecular Sequence Data; D009841:Oligonucleotides / Q000737:chemistry*; D011687:Purines; D011743:Pyrimidines; D011804:Quinolines; D013844:Thiazoles / Q000737:chemistry*
chemical_list: D052160:Benzothiazoles; D005456:Fluorescent Dyes; D009841:Oligonucleotides; D011687:Purines; D011743:Pyrimidines; D011804:Quinolines; D013844:Thiazoles; C051000:thiazole orange; D004247:DNA; C030986:pyrimidine; C030985:purine