title: Evidence of 2-aminopurine-cytosine base mispairs involving two hydrogen bonds.
abstract: It is shown that the mutagen base analogue 2-aminopurine is hydrogen-bonded at its 1-ring position when annealed with cytosine in DNA. The presence of stably hydrogen-bonded regions proximal to the 2-aminopurine-cytosine base mispair is a prerequisite for the occurrence of two hydrogen bonds coupling the bases at their 1-3- and 2-2-positions. We consider the possibility that, in the resulting heteroduplex base mispair, 2-aminopurine or cytosine may be present as a disfavored imino tautomer.
mesh_terms: D015075:2-Aminopurine; D000225:Adenine / Q000031:analogs & derivatives; D001482:Base Composition; D003596:Cytosine; D004247:DNA; D006860:Hydrogen Bonding; D009690:Nucleic Acid Conformation; D009691:Nucleic Acid Denaturation; D011089:Polydeoxyribonucleotides; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature; D013941:Thymine
chemical_list: D011089:Polydeoxyribonucleotides; D015075:2-Aminopurine; D003596:Cytosine; D004247:DNA; D000225:Adenine; D013941:Thymine