title: Effect of flanking sequences on the right- to left-handed transition of a (dA-dT)n tract in supercoiled DNA.
abstract: Alternating (dA-dT)n sequences in supercoiled DNA may undergo a transition to a left-handed conformation in the presence of Ni2+ ions and high NaCl concentration (Nejedlý, K., Klysik, J. and Palecek, E., FEBS Lett. 243, 313-317 (1989)). In this work we have found that ionic conditions necessary for the B-to-Z transition are strongly dependent on the sequences flanking the (dA-dT)n tract. In particular, the presence of 5'-homopyrimidine (C3) and 3'-homopurine (G4) blocks adjacent to the tract were found to facilitate the transition to the left-handed form. Within a constant sequence context it was found that the ionic strength required to promote the transition was inversely proportional to the length of the (dA-dT)n sequence.
authors.affiliation: Institute of Biophysics, Academy of Sciences of the Czech Republic, Brno, Czech Republic.
authors.forename: K
authors.initials: K
authors.lastname: Nejedlý
authors.forename: D M
authors.initials: DM
authors.lastname: Lilley
authors.forename: E
authors.initials: E
authors.lastname: Palecek
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000737:chemistry*; D007477:Ions; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D010957:Plasmids / Q000737:chemistry; D012689:Sequence Homology, Nucleic Acid
chemical_list: D007477:Ions; D004247:DNA