Structure of fibrin networks

The structure of fibrin gels grown at room temperature from fibrinogen solu tions at several fibrinogen concentrations was investigated by means of ela stic light scattering. By combining Classical Light Scattering (CLS) and Lo w-Angle Elastic Light Scattering (LAELS) an overall wavevector range of mor e than two decades was spanned, from 7.8 x 10(2) to 8.3 x 0(5) cm(-1). The scattered intensity distribution I(q) of all the gels was characterized by three different regimes. For q = q(1) similar to 2.5 x 10(3) cm(-1), I(q) e xhibits a maximum which indicates the presence of a long-range order in the gel structure, with an average mesh size xi(1) = 2 xi/q(1)-25 mu m. For q( 1) < q < q(2)(q(2)similar to 1.3x10(5) cm(-1)), the scattered intensity dis tribution decays with a power lam characterized by the mass fractal exponen t D-m = 1.20 +/- 0.05, which is typical of branched linear polymers. At lar ger wavevectors, for q > q(2), there is a crossover to a scattering from su rface fractals, where I(q) decays with a power law characterized by an expo nent of similar to -4. The length scale xi(2) = 1/q(2) similar to 80 nm is an estimate of the average diameters of the gel fibers. All our results, in cluding the kinetics of gel formation, can be described in terms of a simpl e model.