The Abderhalden reaction II

Abstract

The technique described in the PROCEEDINGS for May 20, 1914, has been modified to the following, which permits more accurate determination of small differences in proteolysis as measured by the amino acid nitrogen: 0.1 gram of dried placenta substrate, or an approximate equivalent of wet substrate, prepared according to Abderhalden, is incubated with 2 c.c. of serum. The mixture is then diluted with about 20 c.c. of water, heated to boiling, and Merck's dialyzed ferric hydrate (Rona-Michaelis method) is added, 1 c.c. for serum alone, 2 c.c. for serum and substrate. The excess iron is precipitated by adding 0.5 c.c. of 1: 1 solution of crystalline MgSO₄, and the solution is filtered and washed into a small evaporating dish. The solution is concentrated on the water bath to dryness; the residue is redissolved in a few drops of water, and washed completely into the micro-amino-nitrogen apparatus. Serum alone gives 0.18 to 0.28 c.c. of nitrogen gas, duplicates on the same serum agreeing within 0.01 c.c. or closer. The increase due to placenta may be as high as 0.25 c.c. Normal male sera give results varying over about the same range as pregnant sera, although a somewhat greater proportion of pregnant than of male sera give results near the upper limit of the range.