S. Mahadevan et M. Palaniandavar, CHIRAL DISCRIMINATION IN THE BINDING OF TRIS(PHENANTHROLINE)RUTHENIUM(II) TO CALF THYMUS DNA - AN ELECTROCHEMICAL STUDY, Bioconjugate chemistry, 7(1), 1996, pp. 138-143
The binding of Delta-, Lambda-, and rac-[Ru(phen)(3)](2+) (phen = 1,10
-phenanthroline) and Delta-, Lambda-, and rac-[Ru-bpy)(3)](2+). (bpy 2
,2'-bipyridyl) with calf thymus DNA has been examined by cyclic and di
fferential pulse voltammetric techniques to obtain structural insight
into the noncovalent binding of the enantiomers to DNA. The insignific
ant shift in Ru-II/Ru-III peak potentials on the addition of DNA sugge
sts that both the oxidized and reduced forms bind to DNA to the same e
xtent. Interestingly, DNA selectively decreases the peak currents of D
elta-[Ru(phen)(3)](2+) but not those of the Lambda-enantiomer; rac-[Ru
(phen)(3)](2+) exhibits an intermediate behavior, thus suggesting that
the Delta-form exhibits significant selectivity for B-DNA. The bindin
g constants (K-2+) and binding site sizes (s) have been determined fro
m the decrease in the peak currents. The binding constant (K-2+) of De
lta-[Ru(phen)(3)](2+) is on the order of 10(4) M(-1) which is less tha
n that for proven intercalators. In contrast, the electrochemical beha
vior of all three forms of [Ru(bpy)(3)](2+) remains almost unaffected
in the presence of DNA, suggesting that the complexes might reside on
the hydrophilic coat of the DNA helix.