On enzymatic clotting processes. Part 3.—Flocculation rate constants of paracasein and fibrin

Abstract

Flocculation rate constants of micellar paracasein and fibrin have been determined from the lag phase in the enzymatic clotting. Without exception these rate constants turn out to be very small. Different arguments are put forward to demonstrate that the retardation in the clotting of paracasein is chiefly of a steric nature. The activation energy of the clotting process becomes negative beyond 310 K, which is ascribed to the growing influence of the London–van der Waals attraction as the micelles become discharged by the enzyme.

The rate constants of fibrin measured from the lag phase have been compared with those estimated from early light scattering results of Steiner and Laki. In both cases rate constants are found to decrease with increasing ionic strength. This is consistent with the proposed mechanism of fibrin polymerization (Ferry; Doolittle), in which rodlike particles form staggered overlaps which are held together by electrostatic forces.