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Effect of the Position and Number of Positive Charges on the Intercalation and Stacking of Porphyrin to Poly[d(G-C)2] and Poly[d(A-T)2]

2008년 8월 12일 12시 10분 46초
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목 <발표Ⅱ>
저자 및
JIN BIAO, 안정은1, 이지훈1, 김석규1
영남대학교 화학과, China
1영남대학교 화학과, Korea
The effect of the number and position of the positive charges on porphyrin with respect to the mode of binding to poly[d(G-C)2](GC) and poly[d(A-T)2](AT) were investigated by absorption, CD and LD. TMPyP produces a negative CD and wavelength independent reduced LD spectra in the Soret region when associates with GC. These spectral characteristics have been considered as diagnostic for intercalation. In contrast, both trans - and cis-BMPyP, where the number of positive charges was reduced to two, multisignate CD and strong wavelength dependent LDr spectra were observed, indicating that these porphyrins do not intercalate. Therefore, four positive charges are required for TMPyP intercalation. When associated with AT, trans-BMPyP exhibited a positive CD signal at a low R ratio with the appearance of a bisignate CD on increasing the mixing ratio, suggestive of binding at the groove of the double helix at low mixing ratios, with stacks on increasing the mixing ratio. Conversely, no monomeric binding was evident in the bis-BMPyP: bisignate CD spectrum; hence, only the stacking mode was found for bis-BMPyP, even at the lowest R ratio, suggesting the importance of the position of the positive charges in determining monomeric groove binding or stacking. The binding geometries of trans- and cis-BMPyP were similar when associated with AT as adjudged from the similar LDr spectrum. When associated with DNA, TMPyP exhibited similar spectral properties with that of the TMPyP-GC complex, indicating intercalation of TMPyP between DNA base pairs. On the other hand, CD and LDr characteristics of both trans- and cis-BMPyP-DNA complex resemble that complexed with AT at a high R ratio suggesting that both porphyrin stacked along the DNA stem.