Spontaneous Assembly of an Organic-Inorganic Nucleic Acid Z-DNA Double-Helix Structure.

Herein, we report a hybrid polyoxometalate organic-inorganic compound, Na2 [(HGMP)2 Mo5 O15 ]⋅7 H2 O (1; where GMP=guanosine monophosphate), which spontaneously assembles into a structure with dimensions that are strikingly similar to those of the naturally occurring left-handed Z-form of DNA. The helical parameters in the crystal structure of the new compound, such as rise per turn and helical twist per dimer, are nearly identical to this DNA conformation, allowing a close comparison of the two structures. Solution circular dichroism studies show that compound 1 also forms extended secondary structures in solution. Gel electrophoresis studies demonstrate the formation of non-covalent adducts with natural plasmids. Thus we show a route by which simple hybrid inorganic-organic monomers, such as compound 1, can spontaneously assemble into a double helix without the need for a covalently connected linear sequence of nucleic acid base pairs.

Theobrominium perchlorate dibenzo-18-crown-6 3.25-hydrate.

The co-crystal, C7H9N4O2 (+)·ClO4 (-)·C20H24O6·3.25H2O, consists of theobrominium (3,7-di-methyl-2,6-dioxo-1H-purin-9-ium) cations, perchlorate anions and dibenzo-18-crown-6 and water mol-ecules. The crown ether is in a bent conformation, in which the planes of the aromatic rings subtend an angle of 63.7 (1)°. Inter-molecular O-H⋯O hydrogen bonding between the water mol-ecules and the O atoms of the cyclic ether delimit an empty space reminiscent of a hollow cage. The water mol-ecules are additionally linked to the cations by N-H⋯O hydrogen bonding. One of the positions of the water molecules is occupied only fractionally (25%) and is located outside this framework.

Dihydro-nium tetra-chromate(VI), (H(3)O)(2)Cr(4)O(13).

The crystal structure of (H(3)O)(2)Cr(4)O(13) is isotypic with K(2)Cr(4)O(13). The finite tetra-chromate anion in the title structure consists of four vertex-sharing CrO(4) tetra-hedra and exhibits a typical zigzag arrangement. The crystal packing is stabilized by hydrogen bonds between these anions and hydro-nium cations. The two different hydro-nium cations are surrounded by nine O atoms of tetra-chromate anions, with O⋯O distances ranging between 2.866 (8) and 3.282 (7) Å.