Nonclottable fibrin obtained from partially reduced fibrinogen: characterization and tissue plasminogen activator stimulation.

Out of 29 disulfide bonds in human fibrinogen, 7 were cleaved during limited reduction under nondenaturing conditions in calcium-free buffer. 2 Aα442Cys-Aα472Cys and 2 γ326Cys-γ339Cys intrachain disulfide bonds in the carboxy-terminal ends of the Aα- and γ-chains and the symmetrical disulfide bonds at γ8Cys, γ9Cys, and Aα28Cys. We studied the loss of thrombin clottability that followed limited reduction and the increase in the susceptibility of the fibrinogen Aα19-Aα20 bond to hydrolysis by thrombin