Dextran sulphate: the relation of molecular features to biological properties.

In a previous paper (Ricketts, 1952a) a series of dextran sulphate preparations varying widely in molecular weight and sulphur content was described. The biological properties of these compounds were examined by Walton (1951, 1952), who found that molecular weight was the principal feature determining toxicity, the smaller molecules being the least toxic. At molecular weights (MN) of the order of 7,000 a blood anticoagulant activity of about 15 international heparin units per mg. was attained when the degree of sulphation exceeded an average of 1.3 sulphate groups per glucose unit. It is in this region, where therapeutically useful anticoagulant activity is to be found, that a more detailed exploration of the relation between molecular features and biological properties than was provided by earlier work is necessary. The fractional precipitation of dextran sulphate from solution brings about, to some extent, a separation of molecular sizes. Exploration of the biological properties of such fractions provides an indication of the optimum molecular weight distribution in dextran sulphate intended for clinical use as an anticoagulant.