Desmin filaments studied by quasi-elastic light scattering

We studied polymers of desmin, a muscle-specific type ill intermediate fila ment protein, using quasi-elastic light scattering. Desmin was purified fro m chicken gizzard. Polymerization was induced either by 2 mM MgCl2 or 150 m M NaCl. The polymer solutions were in the semidilute regime. We concluded t hat the persistence length of the filaments is between 0.1 and 1 mu m. In a ll cases, we found a hydrodynamic diameter of desmin filaments of 16-18 nm. The filament dynamics exhibits a characteristic frequency in the sense tha t correlation functions measured on one sample but at different scattering vectors collapse onto a single master curve when time is normalized by the experimentally determined initial decay rate.