The Interaction of TOEPyP4 and ZnTOEPyP4 Porphyrins with G-Quadruplexes

The methods of Circular Dichroism and UV/Vis spectrophotometry were used to study the influence of two cationic porphyrins meso-tetra-(4N-oxyethylpyridyl) porphyrin (TOEPyP4) and its Zn-containing derivative (ZnTOEPyP4) on the G-quadruplex conformation of d[5'-A(GGGTTA)3GGG-3'] sequence of human telomeric DNA. The analysis of the results indicates a single binding site for these porphyrins, but it differs depending on the porphyrin. It is assumed that TOEPyP4 binds parallel to the quartet plane on the outer surface of the G-quadruplex (external π-π stacking), and the binding of ZnTOEPyP4 also occurs externally, but in the groove of the lateral surface of the G-quadruplex (groove binding).