title: [Parallel double helical DNA. 1. Evidence for the existence of a spiral A-T-paired base].
abstract: The dependence of UV and CD spectra of oligonucleotide 3'-d(ApTpApTpApTpApTpApTp)-O(CH2)6O-5'-(pApTpApTpApTpApTp ApT) (eicosamer) in aqueous solution at pH 7 in the presence of 0.5 M NaCl on temperature and concentration was studied. It was shown that the eicosamer in concentrations below 5.10(-4) M forms a parallel stranded hairpin. From the thermal denaturation profile the thermodynamic parameters of parallel hairpin formation were determined. The values of delta H0, delta S0 and Tm were -90 +/- 8 kJ/mol, -300 +/- 20 J.mol-1.K-1 and 40.5 degrees C, respectively. The CD spectra of the parallel helix differ from those of B-form DNA by reduction of extreme magnitude at approximately 265 nm and appearance of a negative effect at approximately 285 nm.
authors.forename: A K
authors.initials: AK
authors.lastname: Shchelkina
authors.forename: Iu P
authors.initials: IuP
authors.lastname: Lysov
authors.forename: I A
authors.initials: IA
authors.lastname: Il'icheva
authors.forename: A A
authors.initials: AA
authors.lastname: Chernyĭ
authors.forename: Iu B
authors.initials: IuB
authors.lastname: Golova
mesh_terms: D001482:Base Composition; D002942:Circular Dichroism; D004278:DNA, Superhelical; D009690:Nucleic Acid Conformation; D013056:Spectrophotometry, Ultraviolet
chemical_list: D004278:DNA, Superhelical
vernacular_title: Parallel'nye dvoĭnye spirali DNK. 1. Dokazatelstvo sushchestvovaniaparallel'noĭ spirali s A-T-sparivaniem osnovaniĭ.