The presence of a Ca2+ bridge within the gamma chain of human fibrinogen.

The presence of Ca2+ increased the mobility of fragment D, and the gamma chain from fibrinogen on polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate, suggesting that a Ca2+ was associated with these fibrinogen derivatives. The mobilities of the constituent chains from fragment D produced under various conditions, indicate that Ca2+ bound to fibrinogen form an intrachain bridge towards the C-terminus of each gamma chain.