Binding Parameters of CuTAllPyP4 and CoTAllPyP4 Porphyrins to DNA Using Adsorption Isotherms

A comparative study of the binding parameters of cationic porphyrins CuTAllPyP4 and CoTAllPyP4 with DNA was conducted based on spectroscopic adsorption isotherms depending on the ionic strength of the solution. The obtained results show that the binding constant of the porphyrin CoTAllPyP4 with DNA is an order of magnitude lower than the binding constant of CuTAllPyP4 regardless of the ionic strength. The presence of hard allylic side radicals with increasing ionic strength increases the tendency of porphyrins to aggregate and form sandwich-like ensembles on the DNA macromolecule (H-aggregates), which leads to a hypsochromic shift in the electronic absorption spectra of the porphyrins CuTAllPyP4 and CoTAllPyP4 regardless of the type of central metal and spatial structure.