Flexibility of Dilauroyl-Phosphatidyl-Nucleoside Wormlike Micelles in Aqueous Solutions

We report an investigation of the structural properties of dilauroyl-phosphatidyl-uridine wormlike micelles by the combined use of static light scattering and small angle neutron scattering techniques. The q -range covered in the reciprocal space is large enough for a complete structural characterization of micellar aggregates, which can be deduced in terms of contour length, persistence length, and cross sectional radius. In particular, the structural parameters have been extracted through a nonlinear least-squares fitting of the experimental spectra by parametrized wormlike chain scattering functions, obtained with Monte Carlo methods. 1,2 This procedure includes excluded volume interactions, micellar polidispersity, and intermicellar effects. The main result is an accurate estimate of micellar flexibility in terms of persistence length (230 Å). We also show that the persistence length for nucleoside derivative surfactants is not a simple function of the surfactant tail length. A modest change in the hindrance and in the chemical nature of the surfactant polar head, as the exchange of uridine with adenine, produces a significant change in the stiffness of the wormlike micelles. The results are compared to most wormlike systems currently investigated and the biologically relevant implications due to the nucleosidic nature of the phospholipid derivative polar head are discussed.