title: The influence of ionic strength on the binding of a water soluble porphyrin to nucleic acids.
abstract: The ionic strength dependences of the binding of tetrakis (4-N-methylpyridyl)porphine (H2TMpyP) to poly(dG-dC) and calf thymus DNA have been determined. For the former system the results are typical of other intercalators, i.e., a plot of log K vs log [Na+] is linear albeit with a slope which suggests that the "effective charge" of the porphyrin is closer to two than the formal charge of +4. For calf thymus DNA, the binding profile is not completely compatible with the predictions of condensation theory. Whereas the avidity of binding does decrease with increasing [Na+] as predicted, of greater interest is the relocation of the porphyrin from GC-rich regions to AT-rich regions as the ionic strength increases.
mesh_terms: D000818:Animals; D002417:Cattle; D002942:Circular Dichroism; D004247:DNA; D007364:Intercalating Agents; D009690:Nucleic Acid Conformation; D009994:Osmolar Concentration; D011089:Polydeoxyribonucleotides; D011166:Porphyrins; D012995:Solubility; D013053:Spectrophotometry; D013950:Thymus Gland
chemical_list: D007364:Intercalating Agents; D011089:Polydeoxyribonucleotides; D011166:Porphyrins; C016681:poly(dG).poly(dC); C021096:tetra(4-N-methylpyridyl)porphine; D004247:DNA