title: Ground and excited state interactions of metalloporphyrin PtTMPyP4 with polynucleotides [poly(dG-dC)]2 and [poly(dA-dT)]2.
abstract: The ground- and excited-state interactions of Pt(ii) meso-tetrakis(4-N-methylpyridyl)porphyrin (PtTMPyP4) with polynucleotides [poly(dG-dC)]2 and [poly(dA-dT)]2 have been investigated using UV/visible, circular dichroism, and steady-state and time-resolved emission spectroscopy. PtTMPyP4 intercalates into [poly(dG-dC)]2 with K∼ 10(6) M(-1). When bound to [poly(dG-dC)]2 in aerated solution there is a six-fold emission enhancement with 18 nm red-shift in emission maximum. Emission lifetimes are biexponential. In the presence of [poly(dA-dT)]2 at least two distinct groove-binding modes are observed, depending on the binding ratio. In [poly(dA-dT)]2 the emission intensity increases by a maximum factor of 17 with no shift in the emission spectrum. Three exponentials were required for lifetime fitting. The lower extent of emission enhancement in the presence of [poly(dG-dC)]2 suggests that a slow electron transfer may take place to guanine, which is significantly less efficient than that previously observed for PtTMPyP4 in the presence of guanosine 5'-monophosphate (GMP). The results are compared to those previously recorded with free base H2TMPyP4.
authors.affiliation: School of Chemistry, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland. keanepa@tcd.ie jmkelly@tcd.ie.
authors.forename: Páraic M
authors.initials: PM
authors.lastname: Keane
authors.forename: John M
authors.initials: JM
authors.lastname: Kelly
mesh_terms: D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D006157:Guanosine Monophosphate / Q000737:chemistry; D008665:Metalloporphyrins / Q000737:chemistry*; D009944:Organoplatinum Compounds / Q000737:chemistry*; D011067:Poly dA-dT / Q000737:chemistry*; D011089:Polydeoxyribonucleotides / Q000737:chemistry*; D011789:Quantum Theory; D013056:Spectrophotometry, Ultraviolet
chemical_list: D008665:Metalloporphyrins; D009944:Organoplatinum Compounds; D011089:Polydeoxyribonucleotides; C544926:platinum(II) tetrakis(N-methyl-4-pyridyl)porphyrin; D011067:Poly dA-dT; C019530:poly(dC-dG); D006157:Guanosine Monophosphate; D004247:DNA