title: Cis-Dichloro(diaminosuccinate diethyl ester)palladium (II) as Pd(II)/Pt(II) model compound for DNA-binding and antitumor properties: solution equilibria of their aqua-, hydroxo-, and/or chloro-species.
abstract: Cis-Dichloro(diaminosuccinic acid)palladium(II), cis-[Pd(H2dasa)Cl2] (I), or cis-dichloro(diaminosuccinate diethyl ester)palladium(II), cis-[Pd(Et2dasa)Cl2] (II) reacts with two equivalents of AgClO4 to give insoluble Pd(dasa) or an aqueous solution of [Pd(Et2dasa) (H2O)2](ClO4)2, respectively. Three solutions of this salt were titrated with NaOH (I = NaClO4 (0.15M),37 degrees C), and 133 E(H+) data (3.5 < or = pH < or = 7) were treated by SUPERQUAD to fit log beta pqr of cis-aquahydroxo-(pqr = 10-1, -5.25(3)) and di-mu-hydroxo-species (20-2, -6.55(1)). At pH > 7 the ester hydrolysis prevents the calculation of log beta 10-2 for the cis-dihydroxo-complex. Another three solutions of such salt were titrated (I = 0.15M (NaClO4), 37 degrees C) with NaOH and NaCl simultaneously using two potentiometric systems (which measure H+ or Cl-). From 147 E(H+) and E(Cl-) data pairs and the above fixed log beta pqr, SUPERQUAD calculations yield log beta pqr for cis-chloro-aqua (pqr = 110, 3.65(1)), cis-chloro-hydroxo (11-1, -2.68 (4)), and cis-dichloro-species (120, 5.86(3)). Simulated and experimental titrations are in good agreement. Circular dichroism spectra of native DNA and drug:DNA complexes suggest that cis-Pd(H2dasa) and cis-Pd(Et2dasa) chelate moieties induce an opening and rotation of the stacked bases in the double helix. This finding is explained by the abundance of each one and of the total neutral and charged species of II in the tested CD solution.
authors.affiliation: Departamento de Química Inorgánica, Universidad de Granada, Spain.
authors.forename: S
authors.initials: S
authors.lastname: González
authors.forename: J M
authors.initials: JM
authors.lastname: Tercero
authors.forename: A
authors.initials: A
authors.lastname: Matilla
authors.forename: J M
authors.initials: JM
authors.lastname: Pérez
authors.forename: V M
authors.initials: VM
authors.lastname: González
authors.forename: C
authors.initials: C
authors.lastname: Alonso
authors.forename: J
authors.initials: J
authors.lastname: Niclós-Gutiérrez
mesh_terms: D000599:Amino Acids, Diamino / Q000737:chemistry*; D000970:Antineoplastic Agents / Q000737:chemistry*; D002942:Circular Dichroism; D002945:Cisplatin / Q000737:chemistry*; D004247:DNA / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D009690:Nucleic Acid Conformation; D009942:Organometallic Compounds / Q000737:chemistry*; D010165:Palladium; D013329:Structure-Activity Relationship
chemical_list: D000599:Amino Acids, Diamino; D000970:Antineoplastic Agents; D008024:Ligands; D009942:Organometallic Compounds; C090283:dichloro(diaminosuccinate diethyl ester)palladium(II); D010165:Palladium; D004247:DNA; D002945:Cisplatin