title: Rotation of periphery methylpyridine of meso-tetrakis(n-N-methylpyridiniumyl)porphyrin (n = 2, 3, 4) and its selective binding to native and synthetic DNAs.
abstract: By utilizing circular and linear dichroism, the binding mode of meso-tetrakis(n-N-methylpyridiniumyl)porphyrin (n = 2, 3, 4) to various DNAs was studied in this work. 2-N-(methylpyridiniumyl)porphyrin(o-TMPyP), in which rotation of the periphery pyridinium ring is prevented, exhibits similar spectral properties when bound to DNA, poly[d(G-C)(2)] and poly[d(A-T)(2)], suggesting a similar binding mode. Close analysis of the spectral properties led us to conclude that o-TMPyP sits in the major groove. However, both 3-N- and 4-N-(methylpyridiniumyl)porphyrin (m- and p-TMPyP), of which the periphery pyridinium ring is free to rotate, intercalate between the basepairs of DNA and poly[d(G-C)(2)]. In the presence of poly[d(A-T)(2)], m-TMPyP exhibits a typical bisignate excitonic CD spectrum in the Soret band, while p-TMPyP shows two positive CD bands. The excitonic CD spectrum of the m-TMPyP-poly[d(A-T)(2)] complex and the positive CD band of the o-TMPyP-poly[d(A-T)(2)] complex were not affected by the presence of the minor groove binding drug, 4',6-diamidino-2-phenylindole (DAPI), indicating that this porphyrin is bound in the major groove. In contrast, two positive CD bands of the p-TMPyP-poly[d(A-T)(2)] complex altered in the presence of DAPI. From the changes in CD spectrum and other spectral properties, a few possible binding modes for p-TMPyP to poly[d(A-T)(2)] are suggested.
authors.affiliation: Department of Chemistry, Yeungnam University, Kyoungsan City 712-749, Republic of Korea.
authors.forename: Soomin
authors.initials: S
authors.lastname: Lee
authors.forename: Young-Ae
authors.initials: YA
authors.lastname: Lee
authors.forename: Hyun Mee
authors.initials: HM
authors.lastname: Lee
authors.forename: Jae Yang
authors.initials: JY
authors.lastname: Lee
authors.forename: Dong Ho
authors.initials: DH
authors.lastname: Kim
authors.forename: Seog K
authors.initials: SK
authors.lastname: Kim
mesh_terms: D001665:Binding Sites; D002942:Circular Dichroism; D004247:DNA / Q000378:metabolism; D008956:Models, Chemical; D011166:Porphyrins / Q000737:chemistry*; D011485:Protein Binding; D011725:Pyridines / Q000737:chemistry*; D013053:Spectrophotometry; D013997:Time Factors
chemical_list: D011166:Porphyrins; D011725:Pyridines; C092399:meso-tetrakis(1-methyl-4-pyridiniumyl)porphyrin; D004247:DNA