Heparin and Concanavalin A interaction: isolation of fraction with higher anticoagulant activity

Heparin and Concanavalin A complexes were studied under different conditions. Interaction was measured by reading the turbidity at 420 nm. The influence of the pH, heparin, and salt concentration was measured. In the presence of salts pH was very critical, and above pH 5.4 the interaction was practically negligible. At pH 4.6 or 5.2 and the lowest salt concentration compatible with buffering, heparin fractions with different anticoagulant specific activities were detected in the precipitate and in the supernatant, after the interaction. In all cases a significative difference was observed in favor of the heparin isolated from the precipitate. Possibility of an artifact was eliminated by using adequate blanks and running the coagulation tests in the presence of an excess of Concanavalin A.