[Studies in the fibrinogen molecule D fragment inactivation protecting fragment]

The interaction was studied between two fragments of bovine fibrinogen isolated from its tryptic hydrolysate: the D fragment, an inhibitor of fibrin-monomer polymerization, and the protector, a fragment inactivating the D fragment. This reaction is relatively rapid: it is completed for several minutes at room temperature and at 37 degrees and is slowed down at 5 degrees. However, the reached level of the D fragment inactivation does not depend upon temperature (within a range from 5 degrees to 37 degrees). Dilution of the incubation mixture under applied conditions caused no dissociation of the D fragment-protector complex. Inactivation of the D fragment by the protector depends on the solution ionic strength; ionic strength 0.13-0.16 is optimal.