title: Parallel purine-pyrimidine-purine triplex: experimental evidence for existence.
abstract: Oligonucleotides 5'-d(CT)5-L-d(AG)5-L-d(GA)5-3' and 5'-d(GA)5-L-d(TC)5-L-d(GA)5-3' [L = pO(CH2CH2O)3p] were studied by thermal denaturation, chemical modification and binding of fluorescent dyes. Both oligonucleotides are shown to fold back on itself twice forming at pH 7 a sufficiently stable triplex ether with antiparallel-oriented oligopurine strands (the first compound) or parallel-oriented oligopurine strands (the second compounds). The parallel triplex is significantly less stable than the antiparallel one. On the basis of conformational modeling, possible types of base tripling in the triplets are proposed. Thus our data provide the first convincingly evidence for the existence of a purine-pyrimidine-purine triplex with parallel orientation of identical strands.
authors.affiliation: V.A. Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow.
authors.forename: A K
authors.initials: AK
authors.lastname: Shchyolkina
authors.forename: O F
authors.initials: OF
authors.lastname: Borisova
authors.forename: E E
authors.initials: EE
authors.lastname: Minyat
authors.forename: E N
authors.initials: EN
authors.lastname: Timofeev
authors.forename: I A
authors.initials: IA
authors.lastname: Il'icheva
authors.forename: E B
authors.initials: EB
authors.lastname: Khomyakova
authors.forename: V L
authors.initials: VL
authors.lastname: Florentiev
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000737:chemistry*; D005456:Fluorescent Dyes; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009841:Oligonucleotides / Q000737:chemistry; D011687:Purines / Q000737:chemistry*; D011743:Pyrimidines / Q000737:chemistry*; D013696:Temperature
chemical_list: D005456:Fluorescent Dyes; D009841:Oligonucleotides; D011687:Purines; D011743:Pyrimidines; D004247:DNA; C030986:pyrimidine; C030985:purine