Fibrin Clots

Abstract

Two kinds of fibrin have recently been distinguished by the test of whether or not they could be dissolved in 30 per cent urea^1,2. Normal physiological plasma-clot is insoluble in urea, whereas the clot obtained by the action of purified thrombin on purified fibrinogen dissolves easily. It has further been established that both a thermolabile component of the serum and calcium ions are needed to form a urea-insoluble clot from the purified fibrinogen–thrombin system. The internal network structure of the two sorts of clot must be different in some way; and since urea-soluble fibrin can also be dispersed by certain solvents which are known to break hydrogen bonds, for example, guanidine and monochloracetic acid, it would appear that this type of network is held together by secondary forces only. In plasma-clot, however, the particle association seems to be reinforced by stronger linkages.