M. Cusumano et al., Stacking surface effect in the DNA intercalation of some polypyridine platinum(II) complexes, INORG CHEM, 38(8), 1999, pp. 1754-1758
The interaction of the platinum(II) polypyridine complexes [Pt(bipy)(2)](2), [Pt(quaterpy)](2+), [Pt(terpy)(n-Rpy)](2+) and [Pt(bipy)(py)(2)](2+) (bi
py = 2,2'-bipyridine; terpy = 2,2':6',2 "-terpyridine; quaterpy = 2,2':6',2
":6 ",2'''- quaterpyridine; n-R = H, 2-CH3, or 4-CH3) with double-helix DN
A has been studied with a variety of experimental techniques. Induced circu
lar dichroism, strong hypochromism and red shifts of the absorption maxima
of the complexes, increase in melting temperature and viscosity of DNA, and
inhibition of the reaction of the complexes with thiourea in the presence
of DNA, characterize the processes. Intercalation, implying the whole molec
ule or part of it, is the suggested binding mode. The binding constants, K-
B, determined spectrophotornetrically at 25 degrees C, pH 7, and I = 0.15 M
, using the McGhee-von Hippel approach, increase in the order [Pt(bipy)(py)
(2)](2+) < [Pt(terpy)(py)](2+) < [Pt(quaterpy)](2+), on increasing aromatic
planar surface extension. The steric interference with double helix of the
methyl group in [Pt(terpy)(2-Mepy)](2+) destabilizes the interaction by re
ducing the stacking surface.