INTERACTIONS OF PORPHYRINYL-NUCLEOSIDES WITH DNA USING THE EXAMPLE OFPORPHYRINYL-THYMIDINE

-pyidinium)porphyrinyl-p-phenylene-5'-O-thymidine, interacting with pl asmid ds DNA showed an 8 nm red-shift of the Soret band. The observed Soret band shift was 4 nm less than the shift of the respective meso-t etra(N-methyl-4-pyridinium)porphyrin which is usually assumed to indic ate intercalation. Experimental spectra and the MMX- and AM-1 calculat ions of a series of model structures further suggest that the investig ated porphyrinyl-thymidine also interacts with adenine due to its nucl eobase. The possibility of intercalation was also viewed based on inte raction of immobilized porphyrin with ds DNA. Theoretical consideratio ns suggested that there are no steric limitations to the formation of a system in which the porphyrinyl-thymidine in question interacts with a molecule of porphyrinyl-adenosine, via A-T base pairing, to join tw o ds DNA molecules.