Intercalation of water-soluble bis-porphyrins into poly(dA)-poly(dT) double helix.
The association constants (K) of nucleic acid monomers with a series of water-soluble bis-porphyrins (bisMC1, bisMC3, bisMC5, bisMC7, and bisMC11) in which two porphyrin units were linked by a methylene chain of various lengths were estimated spectrophotometrically. Among the bis-porphyrins, the K values are similar for each nucleic acid monomer, indicating that the bridging chain length does not affect the association of the bis-porphyrins with the nucleic acid monomers. The melting curves of poly(dA)-poly(dT) in the presence of bisMC3 or bisMC5 were found to be biphasic, suggesting that bisMC3 and bisMC5 are bound to poly(dA)-poly(dT) with a binding mode different from the groove binding exhibited by the corresponding porphyrin monomers. A negative-induced CD peak in the Soret region of bisMC3 and bisMC5 with poly(dA)-poly(dT) is observed and the visible spectral changes of bisMC3 and bisMC5 upon addition of poly(dA)-poly(dT) are accompanied by a large red shift of the Soret band (bisMC3: 21 nm, bisMC5: 23 nm) with substantial hypochromicity (bisMC3: 49%, bisMC5: 40%). Therefore, it is reasonable to conclude that both of the porphyrin units of bisMC3 and bisMC5 intercalate into poly(dA)-poly(dT). In contrast to poly(dA)-poly(dT), the melting curves of poly(dA.dT)(2) in the presence of the bis-porphyrins did not show such biphasic behavior. Together with the CD and visible absorption data, it is certain that these bis-porphyrins do not intercalate into poly(dA.dT)(2).
Okada
H
H
Faculty of Pharmaceutical Sciences, Hokuriku University, 3-Ho, Kanagawa-Machi, Kanazawa, 920-1181, Japan. 97d001@stu.hokuriku-u.ac.jp
Imai
H
H
Uemori
Y
Y
D001671:Biochemistry / Q000379:methods*; D002942:Circular Dichroism; D008956:Models, Chemical; D009690:Nucleic Acid Conformation; D011089:Polydeoxyribonucleotides / Q000737:chemistry* / Q000378:metabolism; D011166:Porphyrins / Q000737:chemistry* / Q000378:metabolism; D012995:Solubility; D014867:Water
D011089:Polydeoxyribonucleotides; D011166:Porphyrins; C449122:bisMC3 cpd; C449121:bisMC5 cpd; C098037:poly(dA)(poly(dT))2; D014867:Water