Showing papers by "Seog K. Kim published in 2005"

Raman spectroscopic studies on interactions of water soluble cationic oxovanadyl (IV) meso-tetrakis(1-methylpyridium-4-yl) porphyrin with nucleic acids

Abstract: Interactions of water soluble cationic oxovanadyl (IV) meso-tetrakis(1-methylpyridium-4-yl)porphyrin (OVIV(TMPyP)4+) with double stranded poly[d(A-T)2], poly[d(G-C)2] nucleotides and calf thymus DNA were studied by the Raman spectroscopic techniques as well as the polarization spectroscopic measurements. The ground state Raman bands of OVIV(TMPyP)4+ observed in the presence of poly[d(A-T)2] were almost the same as those observed in a pure water solution except the slightly up-shifted Raman band (963 cm−1) which is ascribed to the V O stretching mode of six-coordinated complex, OVIV(H2O)(TMPyP)4+. On the other hand, in the presence of poly[d(G-C)2], a markedly up-shifted Raman band was observed at 992 cm−1, indicating that OVIV(TMPyP)4+ interacts with poly[d(G-C)2] by losing the sixth axial ligand. In the presence of calf thymus DNA, the V O stretching band was observed to be resulted by combination of those observed in poly[d(A-T)2] and poly[d(G-C)2]. The polarization spectroscopic studies with these results imply that OVIV(TMPyP)4+ interacts with DNA in different groove binding patterns originated from the formation of five-coordinated adducts in the G-C pair-rich regions and six-coordinated adducts in the A-T pair-rich regions. The down-shifts of core-size sensitive transient Raman bands (ν2 and ν4 modes) in the presence of nucleic acids illustrate an increase of the core-size of porphyrin macrocycle in the excited triplet state. The transient Raman bands related to pyridine group were observed, and they are interpreted to be due to the excited-state charge transfer from porphyrin ring to peripheral substituents.

DNA Mediated Energy Transfer from 4',6-Diamidino-2-phenylindole to Ru(II)((1,10-phenanthroline)2L) 2+ : Effect of Ligand Structure

Abstract: Furthermore, energy transfer frequentlyoccurs along the electron transfer reaction in biologicalsystems. One of the early examples for the electron transferalong DNA appeared from the metallointercalators non-covalently bound to DNA. The luminescence intensity of aDNA intercalator Ru(II)[(1,10-phenanthroline)

DNA sequence analysis of 1-nitropyrene-4,5-oxide and 1-nitropyrene-9,10-oxide induced mutations in the hprt gene of Chinese hamster ovary cells.

Abstract: Nitropyrene, the predominant nitropolycyclic hydrocarbon found in diesel exhaust, is a mutagenic and tumorigenic environmental pollutant that requires metabolic activation via nitroreduction and ring oxidation. In order to determine the role of ring oxidation in the mutagenicity of 1-nitropyrene, its oxidative metabolites, 1-nitropyrene 4,5-oxide and 1-nitropyrene 9,10-oxide, were synthesized and their mutation spectra were determined in the coding region of hprt gene of CHO cells by a PCR amplification of reverse-transcribed hprt mRNA, followed by a DNA sequence analysis. A comparison of the two metabolites for mutation frequencies showed that 1-nitropyrene 9,10-oxide was 2-times higher than 1-nitropyrene 4,5-oxide. The mutation spectrum for 1-nitropyrene 4,5-oxide was base substitutions (33/49), one base deletions (11/49) and exon deletions (5/49). In the case of 1-nitropyrene 9,10-oxide, base substitutions (27/50), one base deletions (15/50), and exon deletions (8/50) were observed. Base substitutions were distributed randomly throughout the hprt gene. The majority of the base substitutions in mutant from 1-nitropyrene 4,5-oxide treated cells were A-->G transition (15/33) and G-->A transition (8/33). The predominant base substitution, A-->G transition (11/27) and G-->A transition (8/27), were also observed in mutant from 1-nitropyrene 9,10-oxide treated cells. The mutation at the site of adenine and guanine was consistent with the previous results, where the sites of DNA adduct formed by these compounds were predominant at the sites of purines. A comparison of the mutational patterns between 1-nitropyrene 4,5-oxide and 1-nitropyrene 9,10-oxide showed that there were no significant differences in the overall mutational spectrum. These results indicate that each oxidative metabolite exhibits an equal contribution to the mutagenicity of 1-nitropyrene, and ring oxidation of 1-nitropyrene is an important metabolic pathway to the formation of significant lethal DNA lesions.

Interaction of Cu(II)-meso-tetrakis(n-N-methylpyridiniumyl)porphyrin (n = 2,3,4) with Native and Synthetic Polynucleotides Probed by Polarized Spectroscopy

Abstract: The interactions of Cu(II)-meso-Tetrakis(n-N-methylpyridiniumyl)porphyrin (n = 2,3,4), respectively referred to as o-, m- and p-CuTMPyP, and DNA, poly[d(A-T) 2 ] and poly[d(G-C) 2 ] were investigated by circular and linear dichroism (CD and LD). In the o-CuTMPyP case, in which the rotation of the pyridinium ring is prevented, the shape of the CD spectrum when associated to DNA and poly[d(A-T) 2 ] resembles and is characterized by a positive band at a low drug to DNA concentration ratio (R ratio) and is bisignate at a high R ratio. The former CD spectrum shape has been attributed to porphyrin that is bound monomerically outside of DNA while the latter can be attributed to those that are stacked. When o-CuTMPyP is bound to poly[d(G-C) 2 ], the excitonic CD appeared at a relatively high R ratio. In contrast, a characteristic negative CD band in the Soret region was apparent for both m- and p-CuTMPyP when bound to DNA and poly[d(G-C) 2 ] at the low R ratios, indicating that the porphyrin molecule intercalates. However, the DNA is bent near the intercalation site and the plane of the porphyrin molecule tilts relative to the DNA helix axis, as judged by the magnitude of the reduced LD. Various stacking patterns were identified by the shape of the CD spectrum for m- and p-CuTMPyP when bound to poly[d(A-T) 2 ]. Three species for the former complex and two for the latter complex were found which may reflect the extent of the stacking.