The interaction between the assembly of chiral zinc (II) porphyrin and DNA- Electron absorption spectrum and CD spectrum studies

Using electron absorption spectra and CD (circular dichroism) spectral we s tudied the interaction between the assembly of chiral amino acid modified p orphyrinatozinc (II) (Thr - TPPZn) and DNA. The helical assembly of Thr - T PPZn can bind to DNA. The amino acid residue of the assembly of L - Thr - T PPZn forms hydrogen bonds with the phosphate chain of DNA, and the binding belongs to external type. As to the assembly of D - Thr - TPPZn, the porphy rin unit forms pi - pi stacking with the base pair of DNA besides the above mentioned hydrogen bonding. In this case, the binding is a partial interca lation. The reason for the different binding mode is that the assembly of L - amino acid modified porphyrinatozinc (II) is left - handed helical, whic h cannot match the right - handed helical of DNA, while the assembly of D - amino acid modified porphyrinatozinc (II) is right - handed helical that c an match the helical of DNA.