title: Dynamics of supercoiled and relaxed pTZ18U plasmids probed with a long-lifetime metal-ligand complex.
abstract: [Ru(bpy)2(dppz)](2+) (bpy = 2,2'-bipyridine, dppz = dipyrido- [3,2-a:2',3'-c]phenazine) (RuBD), a long-lifetime metalligand complex, displays favorable photophysical properties. These include long lifetime, polarized emission, but no significant fluorescence from the complex that is not bound to DNA. To show the usefulness of this luminophore (RuBD) for probing the bending and torsional dynamics of nucleic acids, its intensity and anisotropy decays when intercalated into supercoiled and relaxed pTZ18U plasmids were examined using frequency-domain fluorometry with a blue light-emitting diode (LED) as the modulated light source. The mean lifetimes for the supercoiled plasmids (< tau > = 148 ns) were somewhat shorter than those for the relaxed plasmids (< tau > = 160 ns). This suggests that the relaxed plasmids were shielded more efficiently from water. The anisotropy decay data also showed somewhat shorter slow rotational correlation times for supercoiled plasmids (288 ns) than for the relaxed plasmids (355 ns). The presence of two rotational correlation times suggests that RuBD reveals both the bending and torsional motions of the plasmids. These results indicate that RuBD can be useful for studying both the bending and torsional dynamics of nucleic acids.
authors.affiliation: Department of Oral Biochemistry and Molecular Biology, College of Dentistry and Research Institute for Oral Biotechnology, Pusan National University, Pusan 602-739, Korea. jsokang@pusan.ac.kr
authors.forename: Jung Sook
authors.initials: JS
authors.lastname: Kang
authors.forename: Omoefe O
authors.initials: OO
authors.lastname: Abugo
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Lakowicz
mesh_terms: D004278:DNA, Superhelical / Q000737:chemistry*; D004926:Escherichia coli / Q000737:chemistry; D005454:Fluorescence Polarization; D008024:Ligands; D015335:Molecular Probes; D009690:Nucleic Acid Conformation; D009942:Organometallic Compounds; D010957:Plasmids / Q000737:chemistry*; D012428:Ruthenium; D013816:Thermodynamics
chemical_list: D004278:DNA, Superhelical; D008024:Ligands; D015335:Molecular Probes; D009942:Organometallic Compounds; C413562:RB2Z ruthenium probe; D012428:Ruthenium