title: Conformational conversion of DNA G-quadruplex induced by a cationic porphyrin.
abstract: The interactions between cationic meso-tetrakis(4-(N-methylpyridiumyl))porphyrin (TMPyP4) and the G-quadruplex (G4) of human telomeric single-strand oligonucleotide d(TTAGGG)(2) (S12) have been investigated by means of circular dichroism (CD), UV-visible absorption and fluorescence spectroscopies. It is found that TMPyP4 can preferentially induce the conformational conversion of the G4 structure from the parallel type to the parallel/antiparallel mixture in the presence of K(+), and that it can directly induce the formation of antiparallel G4 structure from the single-strand oligonucleotide S12 in the absence of K(+). Furthermore, the comparable experiments of TMPyP4 with two single-strand oligonucleotides S6 d(TTAGGG) and S24 d(TAGGG(TTAGGG)(3)T) in the absence of K(+) show that TMPyP4 can also induce the formation of antiparallel G4 from S24 but not from S6, indicating that the end-loops of the G4 structure are the key factors for the formation of G4 induced by TMPyP4.
authors: School of Life Science and Technology, Beijing Institute of Technology, Haidian District, Beijing 100081, China. hjzhang@iccas.ac.cn
authors: Huijuan
authors: H
authors: Zhang
authors: Xiao
authors: X
authors: Xiao
authors: Peng
authors: P
authors: Wang
authors: Siping
authors: S
authors: Pang
authors: Feng
authors: F
authors: Qu
authors: Xicheng
authors: X
authors: Ai
authors: Jianping
authors: J
authors: Zhang
mesh_terms: D002942:Circular Dichroism; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D054856:G-Quadruplexes; D006801:Humans; D008954:Models, Biological; D015394:Molecular Structure; D009690:Nucleic Acid Conformation / Q000187:drug effects*; D011166:Porphyrins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D011188:Potassium / Q000737:chemistry / Q000494:pharmacology
chemical_list: D004277:DNA, Single-Stranded; D011166:Porphyrins; C028565:porphyrin pi cation radical; C021096:tetra(4-N-methylpyridyl)porphine; D011188:Potassium