title: Interguanine hydrogen-bonding patterns in adducts with water and Zn-purine complexes (purine is 9-methyladenine and 9-methylguanine). Unexpected preference of Zn(II) for adenine-N7 over guanine-N7.
abstract: Guanine-guanine hydrogen bonding involving the Watson-Crick edge [N(1)H, N(2)H2] of one base and the Hoogsteen edge (N7, O6) of the other is the dominant association pattern in the solid-state structures of two hydrates of 9-ethylguanine (9-EtGH), and in adducts of 9-methylguanine (9-MeGH) with the Zn compounds [ZnCl2(H2O)(9-MeGH-N7)]*(9-MeGH) as well as [ZnCl2(H2O)(9-MeA-N7)]*2(9-MeGH) (9-MeA is 9-methyladenine). The structures of 9-EtGH*2H2O and 9-EtGH*3.5H2O are dominated by polymeric tape structures of the guanine and extended water clusters. In [ZnCl2(H2O)(9-MeGH-N7)]*(9-MeGH) the metalated guanine is involved in hydrogen bonding (GG3 motif) with a free 9-MeGH, which in turn is centrosymmetrically related to itself via hydrogen bonds involving N2H2 and N3 (GG4 motif). In [ZnCl2(H2O)(9-MeA-N7)]*2(9-MeGH) the metalated adenine base interacts via its Watson-Crick edge [N1, N(6)H2] with the sugar edge [N(2)H2, N3] of one of the guanine nucleobases of the GG pair. Crystallization of [ZnCl2(H2O)(9-MeA-N7)]*2(9-MeGH) from an aqueous solution containing 9-MeGH, 9-MeA, and ZnCl2 is fully unexpected in that the anticipated preference of Zn(II) for guanine-N7 is not realized and instead coordination to adenine-N7 is observed. The relevance of [ZnCl2(H2O)(9-MeGH-N7)]*(9-MeGH) and [ZnCl2(H2O)(9-MeA-N7)]*2(9-MeGH) for metal-containing nucleic acid triplex structures is discussed.
authors.affiliation: Departamento de Tecnología Industrial, Universidad Alfonso X El Sabio, 28691 Villanueva de la Cañada, Madrid, Spain. pamochoa@uax.es
authors.forename: Pilar
authors.initials: P
authors.lastname: Amo-Ochoa
authors.forename: Pablo J
authors.initials: PJ
authors.lastname: Sanz Miguel
authors.forename: Oscar
authors.initials: O
authors.lastname: Castillo
authors.forename: Michal
authors.initials: M
authors.lastname: Sabat
authors.forename: Bernhard
authors.initials: B
authors.lastname: Lippert
authors.forename: Félix
authors.initials: F
authors.lastname: Zamora
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives* / Q000737:chemistry; D018360:Crystallography, X-Ray; D006147:Guanine / Q000031:analogs & derivatives* / Q000737:chemistry; D006860:Hydrogen Bonding; D008958:Models, Molecular; D015394:Molecular Structure; D013237:Stereoisomerism; D014867:Water / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry*
chemical_list: D014867:Water; C116701:9-methylguanine; D006147:Guanine; C013115:9-methyladenine; D015032:Zinc; D000225:Adenine