The influence of calcium ions on fibrin polymerization

The influence of calcium ions on the polymerization induced in fibrinogen solutions by thrombin and by Reptilase has been investigated by meansof static and dynamic light scattering in combination with measurements of the release of the fibrinopeptide A. The calcium concentration was varied in the range between 0.3 and 103 calcium ions per fibrinogen molecule. The enzyme concentration was chosen sufficiently low so that it was possible to make quantitative observations as a function of time, in particular, beforethe onset of gelation. Likewise, the influence of calcium ions on the enzymatically induced polymerization of fragment X was studied. The results indicate that there are at least three mechanisms by which calcium can influence the evolution of the polymer system on the path to gelation and clotting. Which mechanism dominates depends upon the calcium concentration.