title: Molecular beacons as probes of RNA unfolding under native conditions.
abstract: Hybridization of fluorescent molecular beacons provides real-time detection of RNA secondary structure with high specificity. We used molecular beacons to measure folding and unfolding rates of the Tetrahymena group I ribozyme under native conditions. A molecular beacon targeted against 15 nt in the 5' strand of the P3 helix specifically hybridized with misfolded forms of the ribozyme, without invading the native tertiary structure. The beacon associated with the misfolded ribozyme 300 times more slowly than with an unstructured oligonucleotide containing the same target sequence, suggesting that the misfolded ribozyme core remains structured in the absence of Mg2+. The rate of beacon hybridization under native conditions revealed a linear relationship between the free energy of unfolding and Mg2+ concentration. A small fraction of the RNA population unfolded very rapidly, suggesting parallel unfolding in one step or through misfolded intermediates.
authors.affiliation: Cell, Molecular and Developmental Biology and Biophysics Program, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218-2685, USA. jfhopkins@jhu.edu
authors.forename: Julia F
authors.initials: JF
authors.lastname: Hopkins
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Woodson
mesh_terms: D004591:Electrophoresis, Polyacrylamide Gel; D005456:Fluorescent Dyes / Q000737:chemistry*; D007700:Kinetics; D008274:Magnesium / Q000737:chemistry; D009690:Nucleic Acid Conformation; D009693:Nucleic Acid Hybridization; D009838:Oligodeoxyribonucleotides / Q000737:chemistry*; D015345:Oligonucleotide Probes / Q000737:chemistry*; D012313:RNA / Q000737:chemistry*; D016337:RNA, Catalytic / Q000737:chemistry; D004124:p-Dimethylaminoazobenzene / Q000031:analogs & derivatives* / Q000737:chemistry
chemical_list: D005456:Fluorescent Dyes; C504807:MB-P3 molecular beacon; D009838:Oligodeoxyribonucleotides; D015345:Oligonucleotide Probes; D016337:RNA, Catalytic; D012313:RNA; D004124:p-Dimethylaminoazobenzene; D008274:Magnesium