The interaction of rhodium(III) with DNA by circular dichroism studies. Comparative behaviour of dimethyltin(IV) and thallium(I)

Abstract

The effect of RhCl3 on DNA helix conformation was studied by circular dichroism spectroscopy and compared to the behaviour of Me2SnCl2 and TINO3; the latter metal-DNA systems have been further studied by ultraviolet and thermal denaturation techniques. Both rhodium(III) and tin(IV) react with the bases of DNA and induce appreciable alterations of the double-helical conformation. Rhodium(III) at low binding ratio causes a stabilization of the DNA B conformation, while at higher structural changes are interpreted in terms of a B to C transition. Tin(IV) produces a ψ form geometry; only at high binding ratios does interaction with the phosphate groups seem to occur. The data for thallium(I) are interpreted in terms of a preferential interaction with the phosphate groups of the DNA chain, causing a stabilization of the double-helical structure of DNA.