title: Experimental and DFT studies on DNA binding and photocleavage of two cationic porphyrins. Effects of the introduction of a carboxyphenyl into pyridinium porphyrin.
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 (H2TMPyP) have been investigated. The DNA-binding behaviors of the two compounds in NaH2PO4 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 H2TMPyP in an intercalative mode. Photocleavage experiments reveal that both two compounds employ 1O2-mediated mechanism in cleaving DNA and H2TMPyP 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 H2TMPyP. These theoretical results can be used to explain their different DNA-binding modes and affinities to a certain extent.
authors.affiliation: MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275, PR China.
authors.forename: Ping
authors.initials: P
authors.lastname: Zhao
authors.forename: Lian-Cai
authors.initials: LC
authors.lastname: Xu
authors.forename: Jin-Wang
authors.initials: JW
authors.lastname: Huang
authors.forename: Jie
authors.initials: J
authors.lastname: Liu
authors.forename: Han-Cheng
authors.initials: HC
authors.lastname: Yu
authors.forename: Kang-Cheng
authors.initials: KC
authors.lastname: Zheng
authors.forename: Liang-Nian
authors.initials: LN
authors.lastname: Ji
mesh_terms: D002412:Cations; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry*; D006358:Hot Temperature; D008027:Light; D008956:Models, Chemical; D008968:Molecular Conformation; D010100:Oxygen / Q000737:chemistry; D011166:Porphyrins / Q000737:chemistry*; D011485:Protein Binding; D011726:Pyridinium Compounds / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods; D013053:Spectrophotometry / Q000379:methods; D014783:Viscosity
chemical_list: D002412:Cations; D011166:Porphyrins; D011726:Pyridinium Compounds; D012997:Solvents; D004247:DNA; D010100:Oxygen