A resonance light-scattering analysis of the suprahelical helixes of nucleic acids induced by 5,10,15,20-tetrakis[4-(trimethyammonio)phenyl]porphine

This paper discusses the usefulness of resonance light-scattering spectroscopy (RLSS)), which can be obtained by using an ordinary spectrofluorimeter, for the analysis of the suprahelical helixes of nucleic acids induced by 5,10,15, 20-tetrakis[4-(trimethyammonio)phenyl]porphine (H(2)tapp). Depending on the acidity of the aqueous solution, the titled porphyrin has two species, [H(2)tapp](4+) and [H(4)tapp](6+). Both species can stack on appropriate conditions along the surface of nucleic acids in the mode of long-range assembly; and this leads to the formation of suprahelical helixes of nucleic acids. Enhanced resonance light-scattering signals can be observed for the porphyrin-induced suprahelical helixes of nucleic acids with the maximal resonance light scattering near to 432 nm for [H(2)tapp](4+) and near to 452 nm for [H(4)tapp](6+). The exciton splitting signals, which are generally associated with the aggregation of porphyrins, as described by molecular-exciton 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 nucleic acids (R) is greater than 0.89. These results indicate that porphyrin-porphyrin interactions occur in the suprahelical helixes of nucleic acids.