A RESONANCE LIGHT-SCATTERING ANALYSIS OF THE SUPRAHELICAL HELIXES OF NUCLEIC-ACIDS INDUCED BY ,15,20-TETRAKIS[4-(TRIMETHYAMMONIO)PHENYL]PORPHINE

This paper discusses the usefulness of resonance light-scattering spec troscopy (RLSS)), which can be obtained by using an ordinary spectrofl uorimeter, for the analysis of the suprahelical helixes of nucleic aci ds induced by 5,10,15, 20-tetrakis[4-(trimethyammonio)phenyl]porphine (H(2)tapp). Depending on the acidity of the aqueous solution, the titl ed porphyrin has two species, [H(2)tapp](4+) and [H(4)tapp](6+). Both species can stack on appropriate conditions along the surface of nucle ic acids in the mode of long-range assembly; and this leads to the for mation of suprahelical helixes of nucleic acids. Enhanced resonance li ght-scattering signals can be observed for the porphyrin-induced supra helical helixes of nucleic acids with the maximal resonance light scat tering near to 432 nm for [H(2)tapp](4+) and near to 452 nm for [H(4)t app](6+). The exciton splitting signals, which are generally associate d with the aggregation of porphyrins, as described by molecular-excito n theory, are observed at 428 nm in the RLS spectra, analogous to the circular dichroism spectra when the molar ratio of [H(2)tapp](4+) to n ucleic acids (R) is greater than 0.89. These results indicate that por phyrin-porphyrin interactions occur in the suprahelical helixes of nuc leic acids.