Full resolution (JPEG) - On this page / på denna sida - II. The Protein Substances - II. Compound Proteins - B. Nucleoproteins - Cleavage Products of the Nucleoproteins - 2. Purine Bases - 3. Pyrimidine Bases
<< prev. page << föreg. sida << >> nästa sida >> next page >>
Below is the raw OCR text
from the above scanned image.
Do you see an error? Proofread the page now!
Här nedan syns maskintolkade texten från faksimilbilden ovan.
Ser du något fel? Korrekturläs sidan nu!
This page has never been proofread. / Denna sida har aldrig korrekturlästs.
PYRIMIDINE BASES. 193
which consists in part of leaf-shaped aggregations and in part of cubical
or prismatic crystals, often with rounded corners. This compound is
used in the microscopic detection of adenine. With the nitric-acid test
and with Weidel’s reaction adenine acts in the same way as hypoxan-
thine. The same is true for i£s behavior with hydrochloric acid and
zinc with subsequent addition of alkali.
The procedure for the preparation and detection of the four above-
described purine bases is as follows: Boiling with 0.5-1 vol. per cent
sulphuric acid, saturating with baryta-water, removing the excess of
barium with CO2, precipitating all the bases as silver compounds
from the strongly ammoniacal filtrate and dissolving them in boiling
nitric acid when the xanthine compound remains in solution on cooling
while the combination with the other three bases precipitate. The silver
xanthine may be precipitated from the filtrate by the addition of ammonia
and the xanthine set free by means of sulphureted hydrogen. The
three above-mentioned silver-nitrate compounds are decomposed by sul-
phureted hydrogen and the guanine separated from the adenine and
hypoxanthine by treatment while hot with ammonia, in which the
guanine is soluble with difficulty. When the above filtrate containing the
adenine and hypoxanthine, which has been, if necessary, freed from
ammonia by evaporation, is allowed to cool, the adenine separates,
while the hypoxanthine remains in solution. According to Balke l —
we can advantageously precipitate the purine bases with copper sulphate
and hydroxylamine. Details for the above methods may be found in
complete hand-books. The same procedures are followed in the quan-
titative estimation of the purine bases in animal organs.2
3. Pyrimidine Bases.
These bodies are closely related to the purines, and pyrimidine,
N=CH
C4H4N2, = HC CH, may be considered as the mother substance thereof.
li II
N—CH
The pyrimidine bases contained in the nucleic acids are cytosine, uracil
and thymine.
N=CNH2
Cytosine, C4H5N3O, = OC CH (6 amino-2 oxypyrimidine), wag first
HN—CH
prepared by Kossel and Neumann from thymus nucleic acid, and then
by Kossel and Steudel and others from various nucleic acids. Wheeler
•See footnote 1, p. 190.
2
See Burian and Hall, Zeitschr. f. physiol. Chem., 38; Kossel ibid., 5-8, Bruhns,
ibid., 14; His and Hagen, ibid., 30.
<< prev. page << föreg. sida << >> nästa sida >> next page >>
