DNA Interactions with Porphyrins Bearing Ammonium Side Chains

Article abstract of DOI:10.1021/jo00103a047

Eleven new porphyrins bearing either tertiary amine or ammonium groups with different spacers in the meso position have been synthesized.Five of them were water-soluble enough for DNA binding studies.UV/vis measurements of some derivatives as a function of pH quantifies the porphyrin core protonation postulated recently by Marzilli et al. with an uptake of two protons and pK values of 6.0 or 6.4, respectively.The porphyrins as well as their Cu(II) or Zn(II) derivatives decrease the viscosity of ds(CT) DNA slightly and increase the melting point of DNA by only up to 1.7 deg C at DNA base pair/ligand ratios of 40.DNA causes either a red shift (/= -7 nm) of the Soret bands.These results as well as the observed small hypochromicities show that all new porphyrins interact with DNA without intercalation.However, their affinity in comparison with other macrocycles bearing four positive charges is, based on ethidium bromide assays with C₅₀ values of 7E-8 to 2E-7 M relatively high and points to groove binding contributions by other than electrostatic forces.