title: Pd(II) complexes of acetylcholinesterase reactivator obidoxime.
abstract: The ability of the acetylcholinesterase reactivator obidoxime (H2L(2+)) to bind palladium(II) cations was evaluated spectrophotometrically at different reaction conditions (pH, reaction time, metal-to-ligand molar ratio). The results showed that immediately after mixing the reagents, pH 7.4, complex species of composition [PdHL](3+) existed predominantly with a value of conditional stability constant lgβ'=6.52. The reaction was completed within 24 hours affording the formation of species [Pd2L](4+) with significantly increased stability (lgβ'=9.34). The spectral data suggest that obidoxime coordinates metal(II) ions through the oximate functional groups. The in vitro reactivation assay of paraoxon-inhibited rat brain acetylcholinesterase revealed that the new complex species were much less active than the non-coordinated obidoxime. The lack of reactivation ability could be explained by the considerable stability of complexes in solution as well as by the deprotonation of oxime groups essential for recovery of the enzymatic activity.
authors.affiliation: Laboratory of Biocoordination and Bioanalytical Chemistry, Department of Analytical Chemistry, Faculty of Chemistry and Pharmacy, "St. Kl. Ohridski" University of Sofia, Sofia, Bulgaria.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Nedzhib
authors.affiliation: Laboratory of Biocoordination and Bioanalytical Chemistry, Department of Analytical Chemistry, Faculty of Chemistry and Pharmacy, "St. Kl. Ohridski" University of Sofia, Sofia, Bulgaria ; Emergency Toxicology Clinic, Military Medical Academy, Sofia, Bulgaria.
authors.forename: Silviya
authors.initials: S
authors.lastname: Stoykova
authors.affiliation: Laboratory of Biocoordination and Bioanalytical Chemistry, Department of Analytical Chemistry, Faculty of Chemistry and Pharmacy, "St. Kl. Ohridski" University of Sofia, Sofia, Bulgaria ; Emergency Toxicology Clinic, Military Medical Academy, Sofia, Bulgaria.
authors.forename: Vasil
authors.initials: V
authors.lastname: Atanasov
authors.affiliation: Laboratory of Biocoordination and Bioanalytical Chemistry, Department of Analytical Chemistry, Faculty of Chemistry and Pharmacy, "St. Kl. Ohridski" University of Sofia, Sofia, Bulgaria.
authors.forename: Ivayla
authors.initials: I
authors.lastname: Pantcheva
authors.affiliation: Institute of Organic Chemistry with Center of Phytochemistry, Bulgarian Academy of Sciences, Sofia, Bulgaria.
authors.forename: Liudmil
authors.initials: L
authors.lastname: Antonov
keywords: Pd(II) complex; acetylcholinesterase reactivation; obidoxime; paraoxon inhibition