title: Relative stabilities of triple helices composed of combinations of DNA, RNA and 2'-O-methyl-RNA backbones: chimeric circular oligonucleotides as probes.
abstract: Described is a systematic study of the effects of varied backbone structure on the stabilities of pyr.pur.pyr triple helices. The effects were measured using six circular 34 base oligonucleotides containing DNA (D), RNA (R) and/or 2'-O-methyl-RNA (M) residues designed to bind a complementary single-stranded purine target strand by triple helix formation. Eighteen different backbone combinations were studied at pH 5.5 and 7.0 by optical melting experiments and the results compared with the stabilities of the corresponding Watson-Crick duplexes. When the target purine strand is DNA, all circles form pH-dependent triple helical complexes which are considerably stronger than the duplexes alone. When RNA is the target, five of the nine complexes studied are of the pH-dependent triplex type and the other four complexes are not significantly stronger than the corresponding duplexes. The results are useful in the design of the highest affinity ligands for single- and double-stranded DNAs and RNAs and also point out novel ways to engender DNA- or RNA-selective binding.
authors.affiliation: Department of Chemistry, University of Rochester, NY 14627, USA.
authors.forename: S
authors.initials: S
authors.lastname: Wang
authors.forename: E T
authors.initials: ET
authors.lastname: Kool
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000737:chemistry*; D004355:Drug Stability; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008024:Ligands; D008745:Methylation; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009691:Nucleic Acid Denaturation; D015345:Oligonucleotide Probes / Q000138:chemical synthesis / Q000737:chemistry* / Q000235:genetics; D012313:RNA / Q000138:chemical synthesis / Q000737:chemistry* / Q000235:genetics; D000079962:RNA, Circular; D013816:Thermodynamics
chemical_list: D008024:Ligands; D015345:Oligonucleotide Probes; D000079962:RNA, Circular; D012313:RNA; D004247:DNA