title: Effect of a 5'-phosphate on the stability of triple helix.
abstract: An effect of 5'-phosphorylation on the stability of triple helical DNA containing pyrimidine:purine:pyrimidine strands has been demonstrated by both gel electrophoresis and UV melting. A 5'-phosphate on the purine-rich middle strand of a triple helix lowers the stability of triple helix formation by approximately 1 kcal/mol at 25 degrees C. The middle strand is involved in both Watson-Crick and Hoogsteen base pairing. In contrast, a 5'-phosphate on the pyrimidine-rich strands, which are involved in either Watson-Crick or Hoogsteen base pairing, has a smaller effect on the stability of triple helix. The order of stability is: no phosphate on either strand > phosphate on both pyrimidine strands > phosphate on purine strand > phosphate on all three strands. Differential stability of triple helix species is postulated to stem from an increase in rigidity due to steric hindrance from the 5'-phosphate. This result indicates that labelling with 32P affect equilibrium in triplex formation.
authors.affiliation: Department of Molecular Biology, Sterling Winthrop Pharmaceuticals Research Division, Malvern, PA 19355.
authors.forename: K
authors.initials: K
authors.lastname: Yoon
authors.forename: C A
authors.initials: CA
authors.lastname: Hobbs
authors.forename: A E
authors.initials: AE
authors.lastname: Walter
authors.forename: D H
authors.initials: DH
authors.lastname: Turner
mesh_terms: D004247:DNA / Q000737:chemistry*; D004591:Electrophoresis, Polyacrylamide Gel; D009690:Nucleic Acid Conformation; D009691:Nucleic Acid Denaturation; D010710:Phosphates / Q000737:chemistry*; D010766:Phosphorylation; D013816:Thermodynamics
chemical_list: D010710:Phosphates; D004247:DNA