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Bioinorganic Chemistry and Applications
Volume 2007 (2007), Article ID 53521, 12 pages
http://dx.doi.org/10.1155/2007/53521
Research Article

Characterization of Copper(II) Interactions with Sinefungin, a Nucleoside Antibiotic: Combined Potentiometric, Spectroscopic and DFT Studies

1Department of Theoretical Chemistry, Faculty of Mathematics, Physics and Chemistry, University of Silesia, 14 Bankowa St., Katowice 40-007, Poland
2Department of Bioinorganic and Biomedicinal Chemistry, Faculty of Chemistry, University of Wrocław, F. Joliot-Curie 14, Wrocław 50-383, Poland
3Department of Chemistry, Faculty of Mathematical, Physical, and Natural Sciences, University of Siena, Via Aldo Moro, Siena I-53100, Italy

Received 11 October 2007; Accepted 9 November 2007

Academic Editor: Imre Sóvágó

Copyright © 2007 Maria Jaworska et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Interactions between sinefungin and copper(II) ions were investigated. Stoichiometry and stability constants of the metal-free system and two mononuclear complexes present in solution were determined on the basis of potentiometric data analysis. The results were compared to the Cu(II)-ornithine system due to structural similarities between both molecules. Combined spectroscopic and theoretical studies allowed for determination of coordination pattern for the Cu(II)-sinefungin complexes. At acidic pH, copper is bound in “glycine-like” coordination mode, identical with that of ornithine. This involves α-amino group and the carboxyl oxygen. At higher pH, a “bis-complex” is formed by two sinefungin molecules. The second ligand binds in equatorial position displacing two water molecules, what results in the stable {2N,2O} coordination. Both axial positions are supposed to be occupied by N1 nitrogen donors of adenine moiety, what is confirmed by DFT calculations. They interact indirectly with copper(II) through water molecules as the result of dominant syn conformation of purine.