54 D. A. L. DAVIES 



depth of not more than 0-5 cm. and exposed to u.v. lamps for 

 15 minutes. 



Properties of the product 

 Chemical and physical properties 



The fmal antigenic fraction (TM2 or SM) gives a stable milky 

 suspension in water but is precipitated by the addition of salt 

 (e.g. o- iM-NaCl). The antigen is insoluble in dimethylsulphoxide, 

 formamide, dimethylformamide, dioxane, sodium thioglycollate 

 solution, or mixtures of chloroform-methanol-water, and is only 

 partly soluble in 6M-urea or guanidine-HCl. It becomes more 

 stable and less opalescent in o* 2 per cent sodium dodecyl sulphate, 

 or 66 per cent acetic acid, or 0*2 per cent deoxycholate at pH 9 

 (tris-phosphate buffer), or i per cent lysolecithin (but not sphin- 

 gomyelin), or in 50 per cent aqueous chloro-ethanol containing 

 o-5M-sucrose. If the pH is raised from 9 to 11, material of a 

 higher nitrogen content is precipitated, leaving a lov;^ nitrogen 

 (3 per cent) component in solution. No solvent has been found 

 in which serological activity is retained, or which gives re- 

 tention of activity when the solvent is replaced with water by 

 dialysis. 



Activity is labile to acid (pH 5), to alkali (over pH 9*0) and to 

 heat (60°, 20 mill.); treatment with ultrasonics (M.S.E. — 

 MuUard drill) disperses the material to an opalescent, more stable 

 solution, but there is loss of activity (Fig. i). Little activity can be 

 found after freeze drying, or even after freezing and thawing a 

 suspension, so purification can only be carried out starting with 

 fresh ascitic fluid, and it has to be carried to completion without 

 freeze drying at any stage. Extraction with organic solvents, or 

 exposure to i per cent Tween-20 (polyoxyethylene sorbitan 

 monolaurate), results in loss of activity. 



The chemical composition of the products is shov^oi in Table 

 III. The active substance is a lipoprotein, containing o- 5 per cent 

 sulphur and not over i per cent hexosamine. There is 0-3 per 



