PROBES OF DNA STRUCTURE AND CONFORMATION (PORPHYRIN BINDING TO DNA).

摘要

The first study lays the groundwork for metal ion studies with DNA by investigating a metal ion prototype, the hydrogen ion (H('+)). ('1)H NMR spectra of the imino, amino and CH-aromatic proton regions of calf thymus DNA were compared with that of four mononucleotides (dAMP, TMP, dCMP, and cyclic GMP) from a pH range of 7 to 2. The order of base protonation on DNA is identical to the order predicted by the pK(,a)'s of the mononucleotides, i.e. C > A > G. The second study involves the interaction of a powerful antitumor drug, (1-(alpha)-pyridylmethylene)-2-((alpha)-pyridylhydrazine) copper(II) chloride (CuPCPH) with DNA. CuPCPH binding to calf thymus DNA was studied by ('1)H and ('31)P NMR, viscosity, flow dichroism, absorption spectroscopy and binding studies. At pH 5.6 and 5.1 (0.01M NaNO(,3)), the apparent binding constant was on the order of 10('5)/M where the bound form of the drug is protonated at the non-coordinated hydrazine nitrogen. The drug proved to be more effective at broadening the ('31)P NMR signal of DNA than Cu('2+), but unable to selectively broaden the G(N-1) imino proton signal of DNA. The data was most consistent with an outside binding mode involving the interaction of the drug with the phosphodiester groups on DNA. This dissertation involves primarily a NMR investigation of the interaction of a series of porphyrin derivatives meso-tetra(1-N-methylpyridyl)porphyrin (TMpyP(1)) and meso-tetra(para-N-trimethylanilinium)porphyrin (TMAP) and several metalloporphyrin derivatives (MTMpyP(1)) with three types of DNA's: (1) non-synthetic DNA's, (2) synthetic DNA polymers and (3) a series of synthetic DNA oligodeoxyribonucleotides (12 or 14 base pairs long). Porphyrins with no or easily removed axial ligands are characteristic of intercalators, i.e. increase the viscosity of linear DNA, unwind closed circular superhelical DNA and induce a large negative flow dichroism. However, ('31)P and ('1)H NMR spectra of the heterogeneous non-synthetic DNA's with TMpyP(4) and Ni(II)TMpyP(4) reveal a complexity indicative of more than one binding interaction. At least two types of binding interactions are apparent where TMpyP(4) binds selectively and symmetrically by an intercalative type of interaction at the 5'CpG3' site of the DNA oligomers, and by a less specific non-intercalative interaction, e.g. outside binding. In contrast, the bulky porphyrin TMAP and the non-planar metalloporphyrins MTMpyP(4) (where M = Fe(III), Co(III), Sn(IV) and Zn(II)) and MTMpyP(2) (where M = Cu(II) and Ni(II)) appear to bind exclusively by outside binding. (Abstract shortened with permission of author.)