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 ...

give 50"h inhibition of binding ( lC5,,) was derived from these graphs. The values for ram proacrosin were as follows: unlabelled fucoidan ( 19.1 nM), dextran sulphate SO0 000 M, (3 1.6 nM), dextran sulphate 5000 M, (251 nM), polyvinylsulphate (326 nM), xylan (299 p ~ ) and mannan ( 1000 p ~ ) . The following solutions were tested. but did not reach 50%) inhibition at the concentrations given: ...

The dextran sulphates resemble heparin in being active inhibitors of several different forms of biological activity, e.g., blood coagulation, serum complement activity, and certain enzyme systems (Walton, 1954). In each case the activity of the dextran sulphate appears to be dependent upon direct interaction with one or more protein components of the biological system under investigation. In fa...