Cyclic Voltammetry of Echinomycin and its Complexes with DNA
Quinoxaline antibiotics are known to be poweful substances with antimicrobial and antimumour activity. Echinomycin (Echi) as a member of this family is characterized by crosslinked octadepsipeptide ring with two quinoxalines (1). Echi is a bis-intercalator which inhibits DNA-directed RNA synthesis at different biological systems. We studied interaction of Echi with double-stranded (ds, native) and single-stranded (ss, denatured) DNA molecules using cyclic voltammetry (CV) with repeated scans. We found that Echi alone is electrochemically active and yields several analytically advantageous CV signals which are strongly dependent on switching potential. Using CV or other electrochemical techniques Echi can be determined at submicromolar concentrations. DNA-Echi complexes were obtained either in solution or at the electrode (with DNA attached to the surface) using the so-called adsorptive transfer stripping voltametry(2,3 ). Differences in voltammograms with ds and ss DNA were found. dsDNA- Echi complex produced specific DNA and Echisignals in agreement with the strong binding of Echi to dsDNA by bis-intercalation. Under the same conditions interaction of Echi with ssDNA resulted in high DNA but very small or no Echi signals suggesting only very weak binding of Echi to ssDNA at the electrode surface. Echi thus appears to be a good candidate for a redox indicator in electrochemical DNA hybridization sensors (4).
1. M.J. Waring, in Molecular aspects of anti-cancer drug-DNA interaction.(S. Neidle and M.J. Waring, Eds.), Vol.1, MacMillan, London, 1993, pp. 213-242.
F. Jelen, A. Erdem* and E. Palecek
Institute of Biophysics, Academy of Sciences of the Czech Republic,