title: Conformation of d(GGGATCCC)2 in crystals and in solution studied by X-ray diffraction, Raman spectroscopy and molecular modelling.
abstract: In the crystal, d(GGGATCCC)2 forms an A-DNA double helix as known from a single crystal X-ray diffraction study. Accordingly, in the Raman spectra of crystals the A-family marker bands at 664, 705, 807 and 1101 cm-1 and the spectral characteristics in the region 1200 to 1500 cm-1 clearly demonstrate the A-form as the dominant conformation. Bands at 691, 850, and 1080 cm-1, however, indicate that a minor fraction of the octamer molecules in the crystal is in an unusual, still not unequivocally identified conformation possibly belonging to the B-family. In solution, the octamer is in B-like conformation as shown by the presence of B-DNA Raman marker bands at 685, 837, 1094 and 1421 cm-1. Molecular modelling techniques lead to three structures with slightly different B-form geometries as the lowest energies models when a sigmoidal dielectric function with the bulk dielectric constant epsilon = 78 and the value q = -0.5e for the effective phosphate charges was used in the calculations. An A-form structure bearing a strong resemblance to the experimentally determined crystal structure becomes the lowest energy model structure when the electrostatic parameters are changed to epsilon = 30 and q = -0.25e, respectively.
authors.affiliation: Max-Delbrück-Center for Molecular Medicine, Berlin-Buch, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Fabian
authors.forename: W
authors.initials: W
authors.lastname: Hölzer
authors.forename: U
authors.initials: U
authors.lastname: Heinemann
authors.forename: H
authors.initials: H
authors.lastname: Sklenar
authors.forename: H
authors.initials: H
authors.lastname: Welfle
mesh_terms: D001483:Base Sequence; D003198:Computer Simulation; D003460:Crystallization; D004247:DNA / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D012996:Solutions; D013059:Spectrum Analysis, Raman; D014961:X-Ray Diffraction
chemical_list: D009838:Oligodeoxyribonucleotides; D012996:Solutions; D004247:DNA