title: Conformational transitions of poly(dA-bromo5dU) and poly(dA-iodo5dU) in solution.
abstract: Extensive circular dichroism studies have been conducted with the title polynucleotides under various solution conditions. The studies provided the following information: (i) The halogen atoms in place of thymine methyl hinder the isomerization into X-DNA. (ii) The brominated but not iodinated polynucleotide isomerizes into Z-DNA in concentrated NaCl+NiCl2. The transition takes place at lower NiCl2 concentrations than with poly(dA-dT). (iii) The iodinated polynucleotide forms an unusual conformation in aqueous solution in which it is very stable. It isomerizes from this conformer into the usual B-type double helix in concentrated ethanol solutions. The isomerization is a two-state cooperative process. (iv) Both title polynucleotides undergo still another two-state cooperative transition in trifluorethanol solutions presumably into A-DNA showing a rather unusual circular dichroism spectrum.
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: Chládková
authors.forename: J
authors.initials: J
authors.lastname: Kypr
mesh_terms: D002942:Circular Dichroism; D007065:Idoxuridine / Q000737:chemistry*; D009690:Nucleic Acid Conformation; D011063:Poly A-U / Q000737:chemistry*; D011067:Poly dA-dT / Q000737:chemistry; D013057:Spectrum Analysis
chemical_list: D011063:Poly A-U; D011067:Poly dA-dT; C018640:poly (dA-BrdU); C073619:poly(dA-IdU); D007065:Idoxuridine