title: Origins of high sequence selectivity: a stopped-flow kinetics study of DNA/RNA hybridization by duplex- and triplex-forming oligonucleotides.
abstract: Stopped-flow UV kinetics and thermal denaturation experiments are used to examine the origins of high sequence selectivity and binding affinity of circular triplex-forming oligonucleotides with single-stranded DNA/RNA targets. These 34-nt probes are hybridized to a series of 12-nt target sequences which are fully complementary or which contain a single mismatch. Also studied for comparison are standard 12-nt Watson-Crick DNA or RNA complements. Several novel findings are described: (1) Circular triplex-forming oligomers bind targets with very high thermodynamic selectivity (up to 8-10 kcal/mol against a single-nucleotide mismatch), while linear strands show only 2-3 kcal/mol selectivity. (2) Rates for triplex formation by circular ligands are much greater than other reported triplex formation modes and are nearly the same as for Watson-Crick duplex formation. (3) DNA-DNA and RNA-RNA hybridization rates are similar for both duplex and triplex formation. (4) For both modes of binding, hybridization rates do not vary when a mismatch is introduced into the target, and, therefore, binding selectivity is reflected in large variations in dissociation, rather than association rates. Finally, (5) binding selectivity of circular ligands becomes significantly greater as pH is lowered; results indicate that the high sequence selectivity of the circular DNA ligand is due in large part to the special stability of the protonated C+G-C triad relative to unprotonated mismatched triads. The results are useful in the understanding of properties of nucleic acid complexes in general and give insight into optimum design for synthetic DNA-binding ligands.
authors.affiliation: Department of Chemistry, University of Rochester, New York 14627, USA.
authors.forename: S
authors.initials: S
authors.lastname: Wang
authors.forename: A E
authors.initials: AE
authors.lastname: Friedman
authors.forename: E T
authors.initials: ET
authors.lastname: Kool
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D004270:DNA, Circular / Q000737:chemistry / Q000378:metabolism; D005434:Flow Cytometry; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D009691:Nucleic Acid Denaturation; D009693:Nucleic Acid Hybridization; D015345:Oligonucleotide Probes / Q000737:chemistry* / Q000378:metabolism; D012313:RNA / Q000737:chemistry* / Q000378:metabolism; D000079962:RNA, Circular; D013816:Thermodynamics
chemical_list: D004270:DNA, Circular; D046911:Macromolecular Substances; D015345:Oligonucleotide Probes; D000079962:RNA, Circular; D012313:RNA; D004247:DNA