Abstract
I have elsewhere shown 1 that the agent in ox-serum which brings about the formation of fertilization-membranes in sea-urchin eggs 2 can be isolated in an impure condition by a process consisting, essentially, in precipitating the substance by barium chloride, re-solution of this precipitate in dilute acid, removal of the excess of barium by excess of sodium sulphate, and reprecipitation by acetone.
The preparations thus obtained were found to be contaminated by a considerable proportion of sodium sulphate, precipitated together with the fertilizing agent by the acetone. They also contained appreciable traces of phosphates. I have obtained a much purer preparation by a process consisting, essentially, in precipitation from the serum by acetone, extraction of the precipitate with hot N/10 HCl, exactly neutralizing the extract with Ba(OH)2, re-dissolving the precipitate in N/10 H2SO4 and reprecipitating it with acetone. The yield from a liter of ox-serum lies between 10 and 40 milligrams.
The substance which is thus obtained is soluble in dilute acids, alkalies and salt-solutions. It is much more rapidly dissolved when these solvents are hot. Its solutions are not coagulated by boiling. It is thrown out of solution by chlorides of the alkaline earths. It yields the Millon, Acree-Rosenheim and xanthoproteic tests for protein. One part of the substance rubbed up in 512,000 parts of sea-water caused membrane-formation in 80 per cent. of Strongylocentrotus purpuratus eggs which had previously been sensitized by 4 minute's immersion in 3/8 m SrCl3.
The active substance, therefore, is either a protein or a peptone, or else, by the above methods of preparation, is precipitated together with a protein or peptone.
I find that Witte's “peptone ” contains the membrane-forming substance, since one part of Il'itte's “peptone” dissolved in 16,000 parts of sea-water caused membrane-formation in 32 per cent. of sensitized purpuratus eggs.
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