title: Transitions of poly(dI-dC), poly(dI-methyl5dC) and poly(dI-bromo5dC) among and within the B-, Z-, A- and X-DNA families of conformations.
abstract: It is shown, using circular dichroism spectroscopy, that poly(dI-dC) is capable to isomerize into both Z-DNA and A-DNA in concentrated NaCl + NiCl2 and trifluoroethanol solutions, respectively. This polynucleotide also undergoes a cooperative, two-state transition in ethanol into a structure which most probably is a canonical B-DNA. This implies that the conformation of poly(dI-dC) is unusual in low-salt aqueous solution. The canonical B-DNA is also adopted by poly(dI-methyl5dC) in trifluoroethanol while this polynucleotide adopts Z-DNA not only in NaCl + NiCl2 but also in the presence of MgCl2. Poly(dI-methyl5dC) partially adopts X-DNA in concentrated CsF and mainly ethanolic solutions. Poly(dI-bromo5dC) isomerizes into Z-DNA not only in concentrated NaCl even in the absence of NiCl2 but also in concentrated MgCl2. This polynucleotide transforms between two distinct variants of Z-DNA in ethanol or trifluoroethanol solutions.
authors.affiliation: Institute of Biophysics, Czechoslovak Academy of Sciences, Brno.
authors.forename: M
authors.initials: M
authors.lastname: Vorlícková
authors.forename: J
authors.initials: J
authors.lastname: Sági
mesh_terms: D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry*; D007536:Isomerism; D015636:Magnesium Chloride; D009690:Nucleic Acid Conformation; D011089:Polydeoxyribonucleotides / Q000737:chemistry*; D012965:Sodium Chloride; D012996:Solutions
chemical_list: D011089:Polydeoxyribonucleotides; D012996:Solutions; D015636:Magnesium Chloride; C031156:poly d(I-C); C069081:polydeoxyinosinic-polydeoxy-(5-methylcytidylic)acid; D012965:Sodium Chloride; C043957:polydeoxyinosinic-polydeoxy-(5-bromocytidylic)acid; D004247:DNA