title: Circular dichroism spectra show that repeating dinucleotide DNAs may form helices in which every other base is looped out.
abstract: We have found that the CD spectrum of poly [d(C-T)] undergoes a marked change upon protonation, taking on the unmistakable features of the spectrum of poly[d(C) x d(C+)]. The acid poly[d9C-T)] structure appears to be one in which each of the T residues is individually looped out of a helix formed by stacked C x C+ base pairs. We also present data for poly[d(C-A)] and review data for the other four possible repeating DNA dinucleotide sequences. These data show that self-complexes in which up to 50% of the residues are extrahelical may be unexceptional.
mesh_terms: D002942:Circular Dichroism; D004247:DNA; D009690:Nucleic Acid Conformation; D011089:Polydeoxyribonucleotides; D012091:Repetitive Sequences, Nucleic Acid; D013329:Structure-Activity Relationship
chemical_list: D011089:Polydeoxyribonucleotides; D004247:DNA