[Isolation and investigation of structural organization of active and inactive forms of fibrinogen D-fragment molecule].

High molecular weight fragment D (M.W. 95 000) which is an effective inhibitor of polymerization of fibrin, and its more low molecular weight form (M.W. 82 000) which has no antipolymerization activity was obtained from fibrinogen by proteolysis. It was shown by the method of scanning microcalorimetry that the active D-fragment consists of four cooperative regions: one thermostable and three non-equal thermolabile. The smallest thermolabile cooperative region (M.W. 13 000) in the inactive D-fragment is absent. It is supposed, that it takes part in the formation of the active centre.