title: Crystal structure of an intermolecular 2:1 complex between adenine and thymine. Evidence for both Hoogsteen and 'quasi-Watson-Crick' interactions.
abstract: The titled complex, obtained by co-crystallization (EtOH/25 degrees C), is apparently the only known complex of the free bases. Its crystal structure, as determined by X-ray diffraction at both 90 K and 313 K, showed that one A-T pair involves a Hoogsteen interaction, and the other a Watson-Crick interaction but only with respect to the adenine unit. The absence of a clear-cut Watson-Crick base pair raises intriguing questions about the basis of the DNA double helix.
authors.affiliation: Department of Organic Chemistry, Indian Institute of Science, Bangalore, India. sosale@orgchem.iisc.ernet.in
authors.forename: Sosale
authors.initials: S
authors.lastname: Chandrasekhar
authors.forename: Tangali R Ravikumar
authors.initials: TR
authors.lastname: Naik
authors.forename: Susanta K
authors.initials: SK
authors.lastname: Nayak
authors.forename: Tayur N Guru
authors.initials: TN
authors.lastname: Row
mesh_terms: D000225:Adenine / Q000737:chemistry*; D020029:Base Pairing; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry; D013696:Temperature; D013941:Thymine / Q000737:chemistry*
chemical_list: D004247:DNA; D000225:Adenine; D013941:Thymine