Comparative studies of ‘bile salts’. 7. Bile acids of the coypu, Myocastor coypus

ANTIGEN OF SHIGELLA DYSENTERIAE 581 0-80-0-85 % P, were free from detectable impurities as shown by fractional solubility tests, electro- phoretic examination and behaviour in the an- alytical ultracentrifuge at pH 7-0.6. Specific polysaccharide dissociates progres- sively from the antigen at alkaline pH values.7. Sedimentation constants at pH's 4-5 and 8 obtained for the phospholipid-free antigen and extrapolated to infinite dilution give approximately the same figure (0-007), which indicates a particle weight of the order of 1 x 107.8. The material possesses an LD60 of 80 ug.in the mouse and induces formation of 'Shiga' agglutinins in rabbits on the injection intraven- ously of 1 ,ug.We wish to thank Dr K. Smith, Lister Institute Research Student (1945-48), for much help in the earlier part of this investigation and Dr B. R. Record, of the Microbiological Research Department, Porton, for freeze-drying facilities and for electrophoretic and ultracentrifugal examinations.One of the authors (W.M.) thanks the Stiftung fur Stipen- dien auf dem Gebiete der Chemie, Bern (1948-SO) for financial support.