Specificity in the interaction between some chiral Co(III) complex ions and DNA in aqueous solution
- 1 January 1972
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases
- Vol. 68, 1213-1226
- https://doi.org/10.1039/f19726801213
Abstract
The binding of some chiral Co(III) complex ions by native DNA in aqueous solution at pH 7.2 has been studied. Equilibrium dialysis and “phase-separation” data show that the affinity for the complex counter-ions used by the polyelectrolyte in 0.01 M NaCl follows the order (–)546[Co(en)3]3+=(+)546[Co(en)3]3+ > (–)546[Co(en)2 L-phe]2+>(–)546[Co(en)2 L-leu]2+. Melting temperature measurements on DNA-complex ions systems indicate that forces other than electrostatic play an important role in the association process investigated. Evidence of a specific site binding is presented in the case of tris(ethylenediamine)cobalt(III). Directional modes of ion pairing are indicated by the changes in the visible c.d. spectra of [Co(en)3]3+ ions in DNA solutions, which are the larger the higher is the percent of bound complex. The peculiar changes in the circular dichroism spectra of DNA in the presence of [Co(en)3]3+ ions in the region of 240–280 nm strongly support the hypothesis of a perturbation in the geometry of the deoxyribonucleic acid secondary structure which accompanies the ion-association complex. Implications of the different structural characteristics of the other complex ions studied on the binding process with DNA are also discussed.Keywords
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