Abstract
In a number of preparations of residue antigen obtained from various micro-organisms, chemical analyses have been carried out to find whether or not the presence of proteins, etc., could be definitely excluded. To this end, total nitrogen has been determined, together with amino-nitrogen before and after acid hydrolysis of the preparation.
The bacteria were grown in large agar plates, washed off with saline and treated in the manner previously described in detail, 1 and the resulting material dried in the dessicator.
Specific precipitin tests were given by saline solutions of the dry material with immune rabbit sera, but insufficient quantities were available to attempt to correlate the dilution at which the test became negative, with the chemical composition. For analysis, the entire specimen was carefully weighed, brought into solution in a few cc. of water, and diluted to a definite volume, usually in a 10 cc. volumetric flask, aliquot portions being taken for separate determinations.
Total nitrogen was determined by the micro-kjeldahl method, titrating with 0.02 N solutions, and the amino-nitrogen determinations were carried out by the micro-Van Slyke method.
Phosphorus was determined by Tisdall's 2 method, after wet ashing.
In those preparations in which sufficient material was obtained for duplicate analyses, agreement was fairly uniform. However, we do not believe that absolute accuracy can be claimed for all the determinations, particularly those of amino-nitrogen after hydrolysis, because of the small quantity available for use, and the relatively low content of nitrogen. The values for total nitrogen are probably the most accurate.
It will be observed that there is a rather considerable variation in each type of nitrogen in the different lots. Considering the results as a whole, one sees that the low and variable total nitrogens point to the presence of a nitrogenous substance associated with a non-nitrogenous compound.
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