title: Single-molecule study of G-quadruplex disruption using dynamic force spectroscopy.
abstract: Guanine-rich sequences in nucleic acids can fold into G quadruplexes, in which four guanines on a single strand combine to form G-tetrad planes stabilized by metallic ions. Sequence motifs which are predicted to form a G quadruplex are found throughout the genome and are believed to regulate a variety of biological processes. Detailed knowledge of the kinetics of G-quadruplex folding and unfolding would provide critical insight into these processes. To probe its structural stability, we used optical tweezers to disrupt single molecules of a single-stranded DNA G4 quadruplex. Dynamic force spectroscopy was employed, in which the distribution of rupture forces was measured for different loading rates and used to infer the nature of the transition state barrier for unfolding of the structure. The distance and height of the energy barriers were extracted for two observed conformations. The energy barrier was found to be close to the folded conformation, resulting in a high disruption force despite the relatively low energy barrier height.
authors.affiliation: Department of Physics, Institute for Physical Science and Technology Biophysics Program, University of Maryland, College Park, 20742-0001, USA.
authors.forename: Michel
authors.initials: M
authors.lastname: de Messieres
authors.forename: Jen-Chien
authors.initials: JC
authors.lastname: Chang
authors.forename: Barbara
authors.initials: B
authors.lastname: Brawn-Cinani
authors.forename: Arthur
authors.initials: A
authors.lastname: La Porta
mesh_terms: D004277:DNA, Single-Stranded / Q000737:chemistry*; D054856:G-Quadruplexes; D006147:Guanine / Q000737:chemistry*; D009690:Nucleic Acid Conformation; D052898:Optical Tweezers; D013057:Spectrum Analysis / Q000379:methods*; D013816:Thermodynamics
chemical_list: D004277:DNA, Single-Stranded; D006147:Guanine