The Precipitation of Human Fibrinogen by Zinc Chloride

Abstract
The precipitation of human fibrinogen by ZnCl2 was studied by measuring the turbidity and the protein concentration in the supernatant (referred as solubility). Different kinetic patterns, either fast or slow, were observed in both solubility and turbidity depending on whether ZnCl2 concentration (CM) was larger or smaller than the critical concentration. In the slow pattern, the increase of the turbidity and the decrease of the solubility both occurred slowly and almost linearly with time. In the fast pattern, these changes occurred rapidly and stationary values were reached within 30 min for the turbidity and 2 h for the solubility. These two stationary values were found to be linearly related to each other. The stationary solubility decreased as CM increased, while it increased with the total amount of the protein. The dissolution of the precipitates was very slow resulting in a practically irreversible precipitation. A gelation model was proposed to account for these characteristic features, according to which fibrinogen molecules were linked to each other through the ’bond’ mediated by a zinc atom.
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