title: Crystalline A-dna: the X-ray analysis of the fragment d(G-G-T-A-T-A-C-C).
abstract: An A-DNA type double helical conformation was observed in the single crystal X-ray structure of the octamer d(G-G-T-A-T-A-C-C), 1, and its 5-bromouracil-containing analogue, 2. The structure of the isomorphous crystals (space group P61) was solved by a search technique based on packing criteria and R-factor calculations, with use of only low order data. At the present stage of refinement the R factors are 31% for 1 and 28% for 2 at a resolution of 2.25 A (0.225 nm). The molecules interact through their minor grooves by hydrogen bonding and base to sugar van der Waals contacts. The stable A conformation observed in the crystal may have some structural relevance to promoter regions where the T-A-T-A sequence is frequently found.
mesh_terms: D001483:Base Sequence; D003461:Crystallography; D004247:DNA; D006860:Hydrogen Bonding; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000138:chemical synthesis; D009841:Oligonucleotides / Q000138:chemical synthesis
chemical_list: D009838:Oligodeoxyribonucleotides; D009841:Oligonucleotides; D004247:DNA