title: [Effect of temperature on the acid-base equilibrium in a DNA molecule].
abstract: The influence of temperature on structural transitions in a protonated DNA molecule has been studied by means of circular dichroism (CD). The measurements were carried at continuos heating over a temperature range from 288 to 343 K at an average rate of (15-30) x 10(-4) K/sec. The objects were diluted DNA solutions (30.3 microM (P)) with supporting electrolyte (NaCl) concentration 1 and 10 mM and pH varying over the range 6.50-3.81 and 6.10-3.66, respectively. The ellipticity was monitored at lambda-245 nm of the negative CD band, which proved to be the most sensitive to the structural transitions in the DNA molecule from the B form to the weakly protonated B+, and then to the S form presumably characterized by Hoogsteen (synGC)+ base pairs. It was shown that the increase of temperature had no effect on the B-->B+-->S transitions in the systems under investigation, although the latter proved to be incomplete because of DNA denaturation. On the basis it was concluded that the enthalpy of the B-->B+-->S transitions in double-stranded DNA is rather small.
authors.forename: S V
authors.initials: SV
authors.lastname: Slonitskiĭ
authors.forename: V Iu
authors.initials: VIu
authors.lastname: Kuptsov
mesh_terms: D000818:Animals; D001483:Base Sequence; D002417:Cattle; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D013696:Temperature
chemical_list: D004247:DNA
vernacular_title: Vliianie temperatury na kislotno-osnovnoe ravnovesie v molekule DNK.