Experiment Station Record, Volume 92, January-June, 1945 Page: 7
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1945] AGRICULTURAL AND BIOLOGICAL CHEMISTRY 7
permutite method, even for amounts as low as y-10lOy/cc. Determinations by either
method were uncertain at concentrations of Oy-2y/cc. "Trigonelline" values obtained
by the method of Perlzweig et al. (E. S. R., 86, p. 712) and presented for
comparison indicate that in human urine Nl-methylnicotinamide comprises nearly
all the trigonelline thus determined. It is noted that since trigonelline does not affect
the fluorescence measurement it is not necessary to omit trigonelline-containing foods
(coffee, legumes) when nicotinic acid excretion tests are conducted by the direct
The direct colorimetric determination of urea in blood and urine, S. B. BARKER
(Jour. Biol. Chew., 152 (1944), No. 2, pp. 453-463, ills. 3).-The author describes a
direct colorimetric procedure in which the urea is condensed with diacetyl monoxime
in the presence of sulfuric acid, and the resulting color enhanced by the addition of
potassium persulfate. From 10y to 150y of urea N, corresponding to 10-150 mg.
of urea N per 100 cc. of blood, can be determined. By a supplementary dilution, this
range can be extended to 250 mg. percent.
The method gave results on human blood filtrates and urines the same as those
given by urease. The colorimetric results on dog urine also were very close to the
urease values, but, in the case of dog blood, this procedure indicated from 1 to 6 mg.
percent more "urea N" than the urease method shows to be present. The discrepancy
was largely removed by treating the Somogyi zinc filtrate with permutite. The author
notes, however, that such a modification "is entirely empirical, since the extra color
cannot be attributed to any specific substance."
The fluorescence of vitamin A.-II, Ultraviolet absorption of irradiated vitamin
A, H. SOBOTKA, S. KANN, W. WINTERNITZ, and E. BRAND (Jour. Amer. Chem.
Soc., 66 (1944), No. 7 pp. 1162-1164, illus. 3).-The nature of the highly fluorescent
substance responsible for the greenish fluorescence previously observed upon ultraviolet
irradiation of alcoholic solutions of vitamin A esters (E. S. R., 91, p. 249)
was investigated by a study of the ultraviolet absorption spectra of such solutions in
the course of irradiation. The irradiated solution of vitamin A acetate in ethanol
showed four absorption bands at wave lengths of 275, 328, 345-346, and 364-365 mg.
This spectrum suggested the presence of more than five conjugated double bonds.
The second wave length, 328 mn,, was identical with that of vitamin A. The three
longer wave lengths coincided with those of the absorption bands of the isoanhydro
vitamin A, suggesting that the highly fluorescent irradiation product, while not identical
with isoanhydro vitamin A, may constitute an excited form of the latter. The
chromogenic power of irradiated vitamin A in the Carr-Price reaction was not
greatly impaired until a secondary oxidative photoreaction led to a decrease and
eventual disappearance of fluorescence. The absorption band at 275 mp was apparently
due to a chromogenic product of a less specific and possibly independent
oxidative degradation of vitamin A.
The assay of purified proteins, enzymes, etc., for "B vitamins," R. J. WILLIAMS,
F. SCHLENK, and M. A. EPPRIGHT (Jour. Amer. Chem. Soc., 66 (1944),
No. 6, pp. 896-898) .-This investigation, carried out to gain insight into the possible
importance of B vitamins as prosthetic groups in proteins known to possess unusual
physiological functions, involved determinations of the various B vitamins, except
riboflavin, in 33 protein, enzyme, hormone, and virus preparations; riboflavin was
not determined, since its absence was suggested by absence of characteristic coloration
of the preparations. Of the samples tested only two, namely, pancreatic amylase
and the yeast carboxylase, contained significant amounts of any of the vitamins.
The pancreatic amylase, a high potency preparation capable of yielding 11,000 times its
weight of maltose, contained 4.1 mg. inositol per gram, and the carboxylase, in
addition to the expected high thiamine value, yielded 131y-145y of niacin per gram.
The viruses investigated were found to be nearly devoid of B vitamins; in this they
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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/m1/20/: accessed October 23, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.