title: A note on crystal packing and global helix structure in short A-DNA duplexes.
abstract: A simple relation exists between the packing density in crystals of short A-DNA duplexes and their global double-helical structure. The volume per nucleotide pair shows a linear inverse correlation with the mean displacement of base pairs from the best straight helix axis. The mean displacement is a measure of major groove depth and varies between -3.3 A and -4.9 A in A-form oligonucleotides analysed in the crystalline state. Since the mean displacement of base pairs from the helix axis determines other helical parameters such as base-pair longitudinal slide, its correlation with crystal packing is of considerable interest. The displacement-packing correlation is very clear for octamer duplexes which crystallize in three different lattices. Longer A-helical fragments sometimes deviate from the rule. It may be speculated whether A-form duplexes not completing a full helical turn are especially prone to distortions due to packing in crystals or arising from intermolecular contacts in solution.
authors.affiliation: Abteilung Saenger, Institut für Kristallographie, Freie Universität Berlin, FRG.
authors.forename: U
authors.initials: U
authors.lastname: Heinemann
mesh_terms: D001483:Base Sequence; D003460:Crystallization; D004247:DNA / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D014961:X-Ray Diffraction
chemical_list: D004247:DNA