Electrochemical studies of the interaction of metal chelates with DNA. 4. Voltammetric and electrogenerated chemiluminescent studies of the interaction of tris(2,2'-bipyridine)osmium(II) with DNA.
Cyclic voltammetric and electrogenerated chemiluminescent data were used to study the binding of tris(2,2'-bipyridine)-osmium(II), Os(bpy)3(2+), an electrostatic binder, to calf thymus DNA. The oxidized form of the osmium complex, Os(bpy)3(3+), has a stronger association to DNA than the reduced form, Os(bpy)3(2+), as indicated by the negative shift of E0' of the CV waves (K3+/K2+ = 3.35). The calculated binding constant, K2+, and binding site size, s, for the Os(byp)3(2+)-DNA system depended slightly on whether a mobile or a static equilibrium was assumed. In 10 mM NaCl, 10 mM Tris pH 7, K2+ = (7.3 +/- 0.4) x 10(3) M-1 and s = 3 base pairs (mobile) and K2+ = (5.0 +/- 0.2) x 10(3) M-1 and s = 3 base pairs (static). Electrogenerated chemiluminescence (ECL) was produced upon oxidation of Os(bpy)3(2+) at a Pt electrode in a solution containing 10 mM C2O4(2-) and 10 mM phosphate at pH 5. Addition of DNA caused a decrease in the emission intensity (I); a plot of I vs relative DNA concentration yielded K2+ = (6.5 +/- 0.5) x 10(3) M-1 and s = 3 base pairs. The osmium complex produced ECL when bound to the DNA molecule with an efficiency of 30% that of the unbound chelate.
Rodriguez
M
M
Department of Chemistry, University of Texas, Austin 78712.
Bard
A J
AJ
D015082:2,2'-Dipyridyl / Q000031:analogs & derivatives*; D002614:Chelating Agents / Q000737:chemistry*; D004247:DNA / Q000737:chemistry* / Q000187:drug effects; D004563:Electrochemistry; D008163:Luminescent Measurements; D009942:Organometallic Compounds
D002614:Chelating Agents; D009942:Organometallic Compounds; C069311:tris(2,2'-bipyridine)osmium(II); D015082:2,2'-Dipyridyl; D004247:DNA