title: When pseudosymmetry and merohedral twinning come across: the case of the d(ApTpApTpApT) oligonucleotide in a hexagonal lattice.
abstract: The d(ApTpApTpApT) deoxyhexanucleotide packs in two different lattice systems: monoclinic and hexagonal. In this study, it is shown that in the hexagonal crystals twinning and pseudosymmetry coexist. The presence of both components resulted in a puzzling space-group determination. Only when a correct model became available [Hoogsteen-DNA; Abrescia et al. (2002), Proc. Natl Acad. Sci. USA, 99, 2806-2811] was it possible to discriminate between twinning and pseudosymmetry. Here, the steps that led to a correct space-group assignment and to the solution of the oligonucleotide structure in the hexagonal lattice by molecular replacement are described.
authors.affiliation: Departament d'Enginyeria Química, Universitat Politècnica de Catalunya, Avenida Diagonal 647, E-080028 Barcelona, Spain. nicola@strubi.ox.ac.uk
authors.forename: Nicola G A
authors.initials: NG
authors.lastname: Abrescia
authors.forename: Juan A
authors.initials: JA
authors.lastname: Subirana
mesh_terms: D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D009841:Oligonucleotides / Q000737:chemistry*
chemical_list: D009841:Oligonucleotides