Ulf Thewalt

The crystal structure of guanosine dihydrate and inosine dihydrate

Crystals of the dihydrates of guanosine (C_(10)H_(13)N_5O_5) and inosine (C_(10)H_(12)N_4O_5) are nearly isostructural. They are monoclinic, space group P2_1, with cell dimensions ɑ = 17·518, b = 11 ·502, c = 6·658 A, β = 98·17° (guanosine) and ɑ = 17·573, b =11·278, c=6-654 A, β = 98·23° (inosine). There are two nucleoside molecules and four water molecules per asymmetric unit. Data were collected on an automated diffractometer; the structures were solved by Patterson and trial-and-error methods and refined to R indices of about 0·035. The structure features hydrogen bonding between purine bases to form ribbons parallel to b and parallel stacking of purine bases along c; the separation between adjacent rings within a stack is 3·3 A. The conformations about the glycosidic C-N bond and the puckerings of the sugar rings arc quite different for the two molecules in the asymmetric unit.

Effects of halogen substituents on base stacking in nucleic acid components: the crystal structure of 8-bromoguanosine.

Abstract The crystal structure of 8-Bromoguanosine dihydrate was determined from three-dimensional diffractometer data. Base stacking in the structure involves close contacts between the bromine atom and the purine moiety of a crystallographically related nucleoside. Comparison with the crystal structure of guanosine suggests that halogen substituents may modify solid state base stacking patterns.

Die Struktur von dl-μ-hydroxo-di-μ-nitro-bis(triamminkobalt)(3+)-trichlorid-hydrat

DL-μ-Hydroxo-di-μ-nitro-bis(triamminecobalt)(3 + )-trichloride hydrate, [(NH_3)_3Co(OH)(N0_2hCo(NH_3)_3]Cl_3. H_20, crystallizes in the monoclinic space group P2_1/c with ɑ = 9·70, b = 6-73, c = 24·57 A and β = 104·3°; there are four formula units in the cell. The structure was determined by the heavy-atom method and refined by three-dimensional least-squares calculations. The final R index for 1397 observed reflections of non-zero weight is 0·067.