title: Strong binding of single-stranded DNA by stem-loop oligonucleotides.
abstract: We report that oligodeoxynucleotides which form stem-loop hairpin structures and which have pyrimidine-rich loops can form strong complexes with complementary single-stranded DNA sequences. Stem-loop oligonucleotides were constructed with a 25-nt T-rich loop and with variable Watson-Crick stems. The complexes of these oligomers with the sequence dA8 were studied by thermal denaturation. Evidence is presented that the complexes are one-to-one, bimolecular complexes in which the pyrimidine loop bases comprise the outer strands in a pyr.pur.pyr triplex, in effect chelating the purine strand in the center of the loop. Melting temperatures for the loop complexes are shown to be up to 29 degrees C higher than Watson-Crick duplex of the same length. It is shown that the presence of a stem increases stability of the triplex relative to an analogous oligomer without a stem. The effect of stem length on the stability of such a complex is examined. Such hairpin oligomers represent a new approach to the sequence-specific binding of single-stranded RNA and DNA. In addition, the finding raises the possibility that such a complex may exist in natural RNA folded sequences.
authors.affiliation: Department of Chemistry, University of Rochester, New York 14627.
authors.forename: D J
authors.initials: DJ
authors.lastname: D'Souza
authors.forename: E T
authors.initials: ET
authors.lastname: Kool
mesh_terms: D001483:Base Sequence; D004277:DNA, Single-Stranded / Q000378:metabolism*; D006358:Hot Temperature; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009691:Nucleic Acid Denaturation; D009838:Oligodeoxyribonucleotides / Q000378:metabolism*
chemical_list: D004277:DNA, Single-Stranded; D009838:Oligodeoxyribonucleotides