title: Triple-helix formation in the antiparallel binding motif of oligodeoxynucleotides containing N(9)- and N(7)-2-aminopurine deoxynucleosides.
abstract: Triplex-forming oligodeoxynucleotide 15mers, designed to bind in the antiparallel triple-helical binding motif, containing single substitutions (Z) of the four isomeric alphaN(7)-, betaN(7)-, alphaN(9)- and betaN(9)-2-aminopurine (ap)-deoxyribonucleosides were prepared. Their association with double-stranded DNA targets containing all four natural base pairs (X-Y) opposite the aminopurine residues was determined by quantitative DNase I footprint titration in the absence of monovalent metal cations. The corresponding association constants were found to be in a rather narrow range between 1.0 x 10(6) and 1.3 x 10(8) M(-1). The following relative order in Z x X-Y base-triple stabilities was found: Z = alphaN(7)ap: T-A > A-T> C-G approximately G-C; Z = betaN(7)ap: A-T > C-G > G-C > T-A; Z = alphaN(9)ap: A-T = G-C > T-A > C-G; and Z = betaN(9)ap: G-C > A-T > C-G > T-A.
authors.affiliation: Department of Chemistry and Biochemistry, University of Berne, Freiestrasse 3, CH-3012 Berne, Switzerland.
authors.forename: S P
authors.initials: SP
authors.lastname: Parel
authors.forename: C J
authors.initials: CJ
authors.lastname: Leumann
mesh_terms: D015075:2-Aminopurine / Q000737:chemistry; D018983:DNA Footprinting; D003850:Deoxyribonuclease I / Q000378:metabolism; D009690:Nucleic Acid Conformation; D009691:Nucleic Acid Denaturation; D009841:Oligonucleotides / Q000737:chemistry* / Q000235:genetics; D011684:Purine Nucleosides / Q000737:chemistry* / Q000235:genetics; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics
chemical_list: D009841:Oligonucleotides; D011684:Purine Nucleosides; D015075:2-Aminopurine; D003850:Deoxyribonuclease I