On the dynamics of semiflexible fibrin gels

The internal dynamics of semiflexible fibrin gels has been investigated by means of dynamic light scattering (DLS). Fibrin gels, grown at room tempera ture from fibrinogen solutions at different NaCl concentrations, exhibit ra ther different structural features. High salt concentrations produce "fine" gels characterized by thin fibers and small mesh sizes, while low salt con centrations give rise to "coarse" gels with thick fibers and much larger me sh sizes. The observed dynamics of these two kinds of gels are quite differ ent as well. "Fine" gels behave as typical semiflexible polymer gels, in wh ich the dynamic structure factor f(q,t) shows an initial monoexponential de cay followed by a stretched exponential decay, f(q,t) similar to exp -(Gamm a (q) t)(beta). Conversely, "coarse" gels exhibit a highly arrested dynamic s, in which the dynamic structure factor does not relax to zero, but decays to a plateau whose value depends on the scattering wavevector q. Moreover, only the stretched exponential decay is observed at the fastest decay time s, with the exponent beta = 0.63+/-0.07 being independently of q. This beha viour can be interpreted as given by the contributions of the internal elas tic modes of many different length scales.