title: Rupture force between the third strand and the double strand within a triplex DNA.
abstract: The rupture force to separate the third strand and the duplex within a triplex DNA was measured by means of atomic force spectroscopy. The tip and the sample surfaces were functionalized by oligodeoxyribonucleotides 5'-TTCTTCTTTCTTTTCCTTTTCTTTCTTCTTACTTCTCTCTCTC TCTCTCT-SH-3'. The sample surface was hybridized with 5'-AAGAAGAAAGAAAAGGAAAAGAAAGAAGAA-3' to form a double strand DNA on the surface prior to the force measurements. These sequences form triple helices with 30 base pairs under a pH of 5.8 and in the presence of 2.0 mM spermine. Signals of rupture of single and multiple triplex DNA were observed in the force distance curves. Rupture force histograms revealed a force of 42.6 +/- 1.9 pN from 24 independent measurements at a tip velocity of 400 nm/s to separate the third strand from duplex DNA. The velocity dependence of the rupture force quantum indicates a thermal dissociation process similar to that of rupturing a ds-DNA. The number of rupture events was controlled by adding oligonucleotides 5'-AAGAAGAAAGAAAAGGAAAAGAAAGAAGAA-3' either to reduce or to initiate triplex formation.
authors.affiliation: Max-Planck Institute for Polymer Research, Mainz 55128, Germany.
authors.forename: Liansheng
authors.initials: L
authors.lastname: Ling
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Butt
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Berger
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000138:chemical synthesis / Q000737:chemistry*; D004277:DNA, Single-Stranded / Q000138:chemical synthesis / Q000737:chemistry; D006046:Gold / Q000737:chemistry; D018625:Microscopy, Atomic Force; D009690:Nucleic Acid Conformation; D009841:Oligonucleotides / Q000138:chemical synthesis / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D004277:DNA, Single-Stranded; D009841:Oligonucleotides; C051802:triplex DNA; D006046:Gold; D004247:DNA