PORPHYRIN AGGREGATION IN AQUEOUS-SOLUTIONS - SMALL-ANGLE AND QUASI-ELASTIC LIGHT-SCATTERING RESULTS

The porphyrin rans-bis(N-methylpyridinium-4-yl)diphenylporphyine (t-H2 Pagg) is known to form in solution large assemblies and supramolecular structures in the presence of polyanions, such as nucleic acids, as a template support. We have studied the aggregation of the unbound porp hyrin in 0.1 M NaCl aqueous solutions. The aggregation process was mon itored by a time resolved small angle light scattering apparatus. The intensity profile of the scattered light as a function of the exchange d wavevector q, conforms to a scattered law for fractal aggregates in the range 0.2-31.4 mu m(-1). An analysis of the intensity data reveals a value of the fractal dimension dr equal to 2.5. Additional dynamic light scattering measurements confirm the presence of almost monodispe rsed aggregates in the mesoscopic range.