Abstract
The DNA-binding affinities and DNA photocleavage abilities of cationic porphyrin, 5-(4-carboxyphenyl)-10,15,20-tris(4-methylpyridiniumyl)porphyrin (CTMPyP), and its reference compound meso-tetrakis( N-methyl-4-pyridiniumyl)porphyrin (H 2TMPyP) have been investigated. The DNA-binding behaviors of the two compounds in NaH 2PO 4 buffer were compared systematically by using absorption, fluorescence and circular dichroism (CD) spectra, thermal denaturation as well as viscosity measurements. The experimental results show that CTMPyP binds to DNA in an outside binding mode, while H 2TMPyP in an intercalative mode. Photocleavage experiments reveal that both two compounds employ 1O 2-mediated mechanism in cleaving DNA and H 2TMPyP can cleave DNA more efficiently than CTMPyP. Theoretical calculations were carried out with the density functional theory (DFT), and the calculated results indicate that the character and energies of some frontier orbitals of CTMPyP are quite different from those of H 2TMPyP. These theoretical results can be used to explain their different DNA-binding modes and affinities to a certain extent.
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