title: Probing conformational isomerizations of double-stranded poly(dA-dT) by a substitution of minor amounts of the thymine methyls with bulky hydrophobic isopropyl groups.
abstract: We probed conformational polymorphism of a synthetic DNA poly(dA-dT) by introducing various small amounts of bulky spherical hydrophobic isopropyl groups into the polynucleotide primary structure. For this purpose, three mixed copolymers of poly(dA-dT,ip5dU) were synthesized in which 2.6%, 8.6% or 14.2% of the polynucleotide pyrimidine bases had the isopropyl group in position 5. The isopropyls made the formation of both A-form and X-form incomplete, and this effect increased with the increasing isopropyl amount in the polynucleotide. However, the polynucleotide isomerization into the A-form was hindered by the isopropyls while the isomerization into the X-form was rather promoted. This observation indicates that, unlike the A-form, the X-form has the base pairs shifted towards the double helix major groove. Z-form was also promoted by the lowest concentration of the isopropyl groups while the most isopropylated poly(dA-dT) aggregated under the Z-form inducing conditions.
authors.affiliation: Institute of Biophysics, Academy of Sciences of the Czech Republic, Brno.
authors.forename: M
authors.initials: M
authors.lastname: Vorlícková
authors.forename: J
authors.initials: J
authors.lastname: Sági
authors.forename: J
authors.initials: J
authors.lastname: Chládková
authors.forename: J
authors.initials: J
authors.lastname: Kypr
mesh_terms: D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry*; D009690:Nucleic Acid Conformation; D011067:Poly dA-dT / Q000737:chemistry*; D013941:Thymine / Q000737:chemistry*
chemical_list: D011067:Poly dA-dT; D004247:DNA; D013941:Thymine