Crosslinking of soluble fibrin and fibrinogen.

Monomeric 125I-desAA-fibrin and 125I-desAABB-fibrin were prepared by treating 125I-fibrinogen with thrombin. Preactivated factor XIII was added to 125I-fibrin/131I-fibrinogen mixtures, and after incubation for 2 and 6 hours, samples were investigated by SDS polyacrylamide gel electrophoresis under reducing conditions. The electrophoresis pattern showed a gamma-gamma band containing both 125I-fibrin and 131I-fibrinogen. These experiments indicate that a fibrin molecule polymerizes with a fibrinogen molecule in a similar way as a fibrin molecule polymerizes to a second fibrin molecule. This type of polymerization results in conformational changes of the molecules involved thus enabling FXIIIa for specific crosslinking reaction. The polymerization of fibrin and fibrinogen molecules as well as the crosslinking of fibrin to fibrinogen molecules seem to represent a mechanism for interrupting the process of further fibrin polymerization.