The 1,4-bis(2′-deoxyadenosin-N 6 -yl)-2S,3S-butanediol intra-strand DNA cross-link arises from bisalkylation of tandem N 6 -dA sites in DNA by R,R-butadiene diepoxide (BDO 2 ). The oligodeoxynucleotide 5′-d(C 1 G 2 G 3 A 4 C 5 X 6 Y 7 G 8 A 9 A 10 G 11 )-3′·5′-d (C 12 T 13 T 14 C 15 T 16 T 17 G 18 T 19 C 20 C 21 G 22 )-3′ contains the BDO 2 cross-link between the second and third adenines of the codon 61 sequence (underlined) of the human N-ras protooncogene and is named the (S,S)-BD-(61-2,3) cross-link (X,Y = cross-linked adenines). NMR analysis reveals that the cross-link is oriented in the major groove of duplex DNA. Watson-Crick base pairing is perturbed at base pair X 6 ·T 17 , whereas base pairing is intact at base pair Y 7 ·T 16 . The cross-link appears to exist in two conformations, in rapid exchange on the NMR time scale. In the first conformation, the β-OH is predicted to form a hydrogen bond with T 16 O 4 , whereas in the second, the β-OH is predicted to form a hydrogen bond with T 17 O 4 . In contrast to the (R,R)-BD-(61-2,3) cross-link in the same sequence [Merritt, W.K., Nechev, L.V., Scholdberg, T.A., Dean, S.M., Kiehna, S.E., Chang, J.C., Harris, T.M., Harris, C.M., Lloyd, R.S., and Stone, M.P. (2005) Biochemistry 44, 10081-10092], the anti conformation of the two hydroxyl groups at C β and C γ with respect to the C β -C γ bond results in a decreased twist between base pairs X 6 ·T 17 and Y 7 ·T 16 , and an approximate 10° bending of the duplex. These conformational differences may account for the differential mutagenicity of the (S,S)-and (R,R)-BD-(61-2,3) cross-links, and suggest that stereochemistry plays a role in modulating biological responses to these cross-links [Kanuri, M., Nechev, L. V., Tamura, P. J., Harris, C. M., Harris, T. M., and Lloyd, R. S. (2002) Chem. Res. Toxicol. 15, 1572-1580.

Key indicatorsSingle-crystal X-ray study T = 295 K Mean (C-C) = 0.003 Å H-atom completeness 90% Disorder in solvent or counterion R factor = 0.043 wR factor = 0.142 Data-to-parameter ratio = 15.9For details of how these key indicators were automatically derived from the article, see Experimental A mixture of Co(CH 3 COO) 2 Á4H 2 O (0.062 g, 0.25 mmol), Hnorf (0.16 g, 0.5 mmol) and water (12 ml) was stirred for 20 min in air. The

The title compound, {[Zn(C14H16N5O3)2]·2H2O}n or [Zn(ppa)2]·2H2O}n, where ppa = 8-ethyl-5,8-dihydro-5-oxo-2-(1-piperazin­yl)-pyrido(2,3-d)-pyrimidine-6-carboxyl­ate, was synthesized under hydro­thermal conditions. The ZnII atom (site symmetry ) exhibits a distorted trans-ZnN2O4 octa­hedral geometry defined by two monodentate N-bonded and two bidentate O,O-bonded ppa monoanions. The extended two-dimensional structure arising from this connectivity is a square grid and the disordered uncoordinated water mol­ecules occupy cavities within the grid. An N—H⋯O hydrogen bond occurs.

Key indicatorsSingle-crystal X-ray study T = 298 K Mean (C-C) = 0.005 Å R factor = 0.037 wR factor = 0.099 Data-to-parameter ratio = 14.7For details of how these key indicators were automatically derived from the article, see

In the title compound, {[Ni(C16H17FN3O3)2]·2H2O}n, the NiII atom (site symmetry ) exists in a distorted trans‐NiN2O4 octahedral geometry defined by two monodentate N‐bonded and two bidentate O,O‐bonded 1‐ethyl‐6‐fluoro‐4‐oxo‐7‐(piperazin‐1‐yl)‐1,4‐dihydroquinoline‐3‐carboxylate (norf) monoanions. The extended two‐dimensional structure is a square grid. N—H...O hydrogen bonds are present in the crystal structure. The water O atom is disordered over two positions; the site occupancy factors are ca. 0.77 and 0.23.