[Mechanism of cross-linking of fibrinogen and its early structural homolog fragment X].

We studied the mechanism of the cross-linking of fibrinogen as well as its closest structural homolog X fragment under the influence of a fibronectin-stabilizing factor (factor XIIIa). The data on elastic and dynamic light scattering indicate the formation of single-stranded polymers without any structural rigidity that acquire a ramified and compact structure upon reaching critical mass. The values of coefficients of translational diffusion, mean-mass molecular weight, averaged scattering factor, and the accumulation of gamma-dimers indicate that preincubation of fibrinogen and fragment X solutions significantly accelerates the enzymatic formation of a covalently bound macromolecular protein complex. We propose that enzymatic cross-linking proceeds only with the gradual accumulation of structurally imperfect molecules of fibrinogen and fragment X that are prone to intermolecular D-D end-to-end contacts.