Experiment Station Record, Volume 92, January-June, 1945 Page: 5
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19453 AGRICULTURAL AND BIOLOGICAL CHEMISTRY 5
biological analysis involved accepted experimental technics, use of the basal medium
of Hutchings and Peterson (E. S. R., 91, p. 19), slightly modified as to glucose
content and adjusted to pH 6.8, and addition of the solution of the "test" amino
acid (at pH 6.8) to the basal medium containing all components except this test
substance. Each assay was run in duplicate at 10 levels of the amino acid, the
tubes after sterilization being inoculated aseptically with one drop of a saline suspension
of the bacterium and inoculated at 37 C. for 72 hr. The lactic acid produced
was determined by titration with standard alkali with bromothymol blue
indicator. Although little or no growth occurred in the absence of asparagine,
cystine, or serine, these amino acids could not be estimated satisfactorily. Leucine,
glutamic acid, tryptophan, and valine, previously assayed with L. arabinasus 17-5
(see above), and arginine, phenylalanine, and tyrosine were satisfactorily analyzed.
It is pointed out that a total of 11 different amino acids may now be analyzed by
the combined methods.
The estimation of the dicarboxylic amino acids by titration, A. C. KIBRICK
(Jour. Biol. Chem., 152 (1944), No. 2, pp. 411-418, illus. 1).-It is pointed out that
although the ninhydrin reaction may not be used in the estimation of the total
Aicarboxylic amino acids, the fact that ninhydrin reacts with both carboxyl groups
of aspartic acid may be utilized in the estimation of this amino acid. The relationships
indicated are summarized as follows: Let g, a, and n represent the moles
of glutamic acid, of aspartic acid, and of nonacidic amino acids, respectively, in
the mixture. Then: Total COOH groups = 2g + 2a + n; ninhydrin-reactive
groups = g + 2a + n; and formaldehyde-reactive N atoms = g + a + n. It is
evident that the combination of these three observations therefore permits the
estimation of the individual dicarboxylic acids as well as that of their total.
The method described comprises an electrometric titration in water and in formaldehyde
solutions supplemented by a gasometric ninhydrin estimation. The
estimations may conveniently be made on less than 1 gm. of protein. The results
of applying these procedures to fractions separated from protein hydrolysates by
adsorption on amberlite IR-4 were uniformly satisfactory. Less satisfactory results
were obtained when the estimations were made on solutions of the crude
barium salts precipitated from the hydrolysates by excess of alcohol.
The estimation of glutamic acid in animo acid mixture by conversion to pyrrolidonecarboxylic
acid was unsatisfactory.
The estimation of the dicarboxylic amino acids in protein hydrolysates, R. K.
CANNAN (Jour. Biol. Chem., 152 (1944), No. 2, pp. 401-410).-The use of a basic
resin, amberlite IR-4, for the separation of the dicarboxylic amino acids from protein
hydrolysates has been investigated. Conditions under which a quantitative
separation of these acids may be obtained are outlined. Estimations of the glutamic
acid and aspartic acid in egg albumin, /-lactoglobulin, and edestin by the adsorption
method are reported.
The microbiological determination of amino acids.-I, Valine, leucine, and
isoleucine, K. A. KUIKEN, W. H. NORMAN, C. M. LYMAN, F. HALE, and L. BLOTTER.
(Tex. Expt. Sta.). (Jour. Biol. Chem., 151 (1943), No. 2, pp. 615-626, iltus.
3).-The method described for determining valine, leucine, and isoleucine utilizes
Lactobacillus arabinosus 17-5 as a test organism in a bioassay procedure similar
to that described by Snell and Wright (E. S. R., 87,, p. 12) for determination of
nicotinic acid but with the use of a suitable mixture of pure amino acids in place
of the casein hydrolysate of the medium for nicotinic acid assay. p-Aminobenzoic
acid and also a concentrate prepared from tomato juice are used in the medium.
This tomato eluate preparation, although rich in p-aminobenzoic acid, apparently
contains in addition some unknown growth stimulating substance for L. arabinoss.,
as, indicated by the increased growth of the organism effected by the addition of
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U.S. Department of Agriculture. Agricultural Research Administration. Office of Experiment Stations. Experiment Station Record, Volume 92, January-June, 1945, book, 1947; Washington D.C.. (digital.library.unt.edu/ark:/67531/metadc5064/m1/18/: accessed May 29, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.