title: An alteration in the structure of the minor groove of duplex DNA induced by the formation of an intermolecular d(GA)n:d(GA)n.d(TC)n triplex.
abstract: A simple homopolymeric purine:purine.pyrimidine, d(GA)n:d(GA)n.d(TC)n, triplex DNA was generated in the presence of magnesium ion at neutral pH. Hydrogen bonding of the N7 positions of guanines and adenines was investigated by 7-deaza base substitutions and protection from chemical modification by dimethyl sulfate (DMS). Chemical modification of this triplex with DMS revealed an unexpected triplex specific hypermodification in the N3 positions of the adenines in addition to the protection in the N7 positions of the guanines. The significance of this increase in the chemical accessibility of the N3 positions of adenines in the minor groove and possible relevance of dehydration to the mechanism of triplex formation and stability is discussed.
authors.affiliation: Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD 20892-0420, USA.
authors.forename: M G
authors.initials: MG
authors.lastname: Kim
authors.forename: R D
authors.initials: RD
authors.lastname: Camerini-Otero
mesh_terms: D000225:Adenine; D001482:Base Composition; D002413:Cations, Divalent; D003596:Cytosine; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D018983:DNA Footprinting; D019175:DNA Methylation; D006147:Guanine; D006863:Hydrogen-Ion Concentration; D008274:Magnesium; D009690:Nucleic Acid Conformation; D009692:Nucleic Acid Heteroduplexes / Q000737:chemistry* / Q000378:metabolism; D011687:Purines; D011743:Pyrimidines; D013941:Thymine; D014867:Water
chemical_list: D002413:Cations, Divalent; D009692:Nucleic Acid Heteroduplexes; D011687:Purines; D011743:Pyrimidines; C051802:triplex DNA; D014867:Water; D006147:Guanine; D003596:Cytosine; D004247:DNA; D008274:Magnesium; D000225:Adenine; D013941:Thymine