Photoinduced Reduction of Manganese(III) meso-Tetrakis(1-methylpyridinium-4-yl)porphyrin at AT and GC Base Pairs
- Photoinduced Reduction of Manganese(III) meso-Tetrakis(1-methylpyridinium-4-yl)porphyrin at AT and GC Base Pairs
- 김석규; 김용희[김용희]; 정상용[정상용]; 이명희[이명희]; 임찬[임찬]; 김윤화; 장윤정; 조대원[조대원]
- DNA-PORPHYRIN INTERACTIONS; RESONANCE RAMAN; NUCLEIC-ACIDS; AXIAL LIGAND; TRANSIENT ABSORPTION; AQUEOUS-SOLUTIONS; HOLE TRANSFER; SPECTROSCOPY; TETRAKIS(4-N-METHYLPYRIDYL)PORPHYRIN; PHOTOCHEMISTRY
- Issue Date
- AMER CHEMICAL SOC
- JOURNAL OF PHYSICAL CHEMISTRY B, v.117, no.33, pp.9585 - 9590
- The photoreduction of water-soluble cationic manganese (III) meso-tetrakis (1-methylpyridium-4-yl)porphyrin (Mn-III(TMPyP)(4+)) bound to a synthetic polynucleotide, either poly[d(A-T)(2)] or poly[d(G-C)(2)], was examined by conventional absorption and circular dichroism (CD) spectroscopy, transient absorption, and transient Raman spectroscopy. Upon binding, Mn-III(TMPyP)(4+) produced a positive CD signal for both polynucleotides, suggesting external binding. In the poly[d(A-T)(2)]-Mn-III(TMPyP)(4+) adduct case, an interaction between the bound porphyrin was suggested. The transient absorption spectral features of Mn-III(TMPyP)(4+) in the presence of poly[d(A-T)(2)] and poly[d(G-C)(2)] were similar to those of the photoreduced products, Mn-II(TMPyP)(4+), whereas Mn-III(TMPyP)(4+) in the absence of polynucleotides retained its oxidation state. This indicated that both poly[d(A-T)(2)] and poly[d(G-C)(2)] act as electron donors, resulting in photo-oxidized G and A bases. The transient Raman bands (nu(2) and nu(4)) that were assigned to porphyrin macrocycles exhibited a large downshift of similar to 25 cm(-1), indicating the photoreduction of Mn-III to Mn-II porphyrins when bound to both polynucleotides. The transient Raman bands for pyridine were enhanced significantly, suggesting that the rotation of peripheral groups for binding with polynucleotides is the major change in the geometry expected in the photoreduction process. These photoinduced changes do not appear to be affected by the binding mode of porphyrin.
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