Molecular weight dependency of the acquired anticomplementary and anticoagulant activities of specifically substituted dextrans.

Dextran that had been substituted with carboxylic and benzylamine sulphonated groups was fractionated by gel chromatography into fractions, of narrow molecular weight distribution from 6000 to 190,000 daltons and of similar chemical composition. The fractions exhibited anticomplementary and anticoagulant activities that rapidly increased with molecular weight and tended to plateau above approximately 20,000 and 40,000 daltons respectively. Anticoagulant activity was lower than that of heparin, whereas the capacity of the fractions to inhibit formation of the classical and alternative C3 convertases in a purified system was similar to that of heparin and their ability to inhibit CH50 in whole serum was higher than that of heparin. The data argue for a random distribution of structurally independent anticoagulant and anticomplementary sites along the macromolecular chains of substituted dextrans.