[The structural transformations of X-oligomers].

Mechanism of self-assembly and the three-dimensional organization of the intermediate soluble forms of X-oligomers in the presence of non-denaturing urea concentration have been studied by dynamic light scattering, analytical ultracentrifugation, and viscometric methods. Swedberg and Kuhn-Mark-Hauwink analysis of the obtained hydrodynamic data accounting the concentration effect on translational friction demonstrated formation of equilibrium single-stranded rod-like protofibrils with end-to-end arrangement of the peripheral domains of X monomers. Upon elongation the single-stranded protofibrils form double-stranded structures through lateral aggregation. We infer that alpha C domains are involved in neither stabilization of the single-stranded structures nor their dimerization.