CD and DSC Investigation of Individual and Complex Influence of Meso-Tetra(4-Oxiethylpyridil) Porphyrin (TOEPyP4) and Its Zn-Complex on DNA

CD spectra of (DNA-TOEPyP4) + ZnTOEPyP4, (DNA-ZnTOEPyP4) + TOEPyP4, and DNA + (TOEPyP4-ZnTO-EPyP4) complexes have been studied. It is shown that CD spectra of these triple complexes significantly differ from the DNA-TOEPyP4 and DNA-ZnTOEPyP4 double complex spectra, and they are not sum of these double complexes. Es-pecially some strong differences in CD spectra of the triple and double complexes were observed when both porphyrins were added simultaneously into the DNA solution. In this case, ZnTOEPyP4 revealed a dominant influence on CD spectrum form. Zn-porphyrin also caused a strong intensity of positive band at 416 nm and a negative band at 437 nm when it was added into solution containing the DNA-TOEPyP4 complex. On the basis of obtained data, it was supposed that the observed significant changes in CD spectra of triple complexes were connected to an altered DNA conforma-tion initiated by intercalation of porphyrin TOEPyP4 into GC-rich sites. The melting process analysis of the double complexes was carried out. The mechanisms of individual and joint influence of the porphyrins on DNA, and influence of binding modes on stability of these complexes are also discussed