title: Crystallographic and spectroscopic studies of d(CCGGTACCGG).
abstract: The decanucleotide sequence d(CCGGTACCGG) crystallizes as a four-way junction at low cobalt ion concentrations (i.e., 1 mM). When the cobalt concentration in the crystallization solution is increased to 5 mM, the sequence crystallizes as resolved B-DNA duplexes. Gel retardation studies of the decamer show both a faint slow-moving band and a much thicker fast-moving band at low cobalt ion concentrations, and only the intense fast-moving band at higher ion concentration. Circular dichroism (CD) spectroscopy of the decamer indicates a structural transition as the cobalt ion concentration in the solution is increased, probably from B-type to A-type DNA. These studies revealed that the oligomer sequence has several conformations and structures accessible to it, in a manner dependent on sequence, ion concentration, and DNA concentration.   [Supplementary materials are available for this article. Go to the publisher's online edition of Nucleosides, Nucleotides & Nucleic Acids for the following free supplemental resources(s): Supplementary Figures 1, 2, and 3.].
authors.affiliation: CAS in Crystallography and Biophysics, University of Madras, Guindy Campus, Chennai, India.
authors.forename: S
authors.initials: S
authors.lastname: Venkadesh
authors.forename: P K
authors.initials: PK
authors.lastname: Mandal
authors.forename: N
authors.initials: N
authors.lastname: Gautham
mesh_terms: D002942:Circular Dichroism; D003035:Cobalt; D003461:Crystallography; D024202:Electrophoretic Mobility Shift Assay; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry*
chemical_list: D009838:Oligodeoxyribonucleotides; D003035:Cobalt