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146 THE PROTEIN SUBSTANCES.
Isoserine (£-amino-a-oxypropionic acid) has been prepared by Ellinger
from diamino-propionic hydrobromide and silver nitrite, and by Neuberg and
Silbermann from the hydrochloric acid combination of diamino-propionic acid.
Other syntheses have been made by Neuberg and Mayer and by Neuberg
and Ascher. 1
COOH
Z-Aspartic acid (aminosuccinic acid), C4H7N04=att , has been
CH.2
COOH
obtained on the cleavage of protein substances by proteolytic enzymes as
well as by boiling them with dilute mineral acids in comparatively small
quantities. This acid also occurs in secretions of sea-snails (Henze 2
)
and is very widely diffused in the vegetable kingdom as the amide
Asparagine (aminosuccinic-acid amide), which seems to be of the
greatest importance in the development and formation of the proteins
in plants. d-Z-Aspartic acid has been prepared synthetically from fumaric
acid and alcoholic ammonia. On putrefaction of aspartic acid, propionic
acid and succinic acid are formed.
/-Aspartic acid dissolves in 256 parts water at 10° C. and in 18.6 parts
boiling water, and on cooling crystallizes as rhombic prisms, and its
4 per cent solution acidified with HC1 has the rotation («)d = +25.7°;
in alkaline solution the acid is levo-rotatory. It forms with copper
oxide a crystalline compound which is soluble in boiling-hot water and
nearly insoluble in cold water, and which may be used in the prepara-
tion of the pure acid from a mixture with other bodies.
The benzoyl-Z-aspartic acid melts at 184-185°. For identification
we make use of the analysis of the free acid and the copper salt, as well
as of the specific rotation.
COOH,
CH(NH2)
^/-Glutamic acid (a-aminoglutaric acid), CsH9N04 = CH2 , is
CH2
COOH
obtained from the protein substances under the same conditions as the
other monamino-acids (see tables on pages 106, 107, 115 and 125) and
from the peptones (Siegfried). It is absent in the protamines and in the
varieties of silk, it occurs only in small amounts with the exception of spi-
der’s web. Hlasiwetz and Habermann obtained 29 per cent from casein
by cleavage with hydrochloric acid, while Kutscher could obtain only
1.8 per cent glutamic acid by cleavage with sulphuric acid. Other
’Ellinger, Ber. d. d. chem. Gesellsch., 37; Neuberg and Silbermann, ibid., 37;,
Neuberg and Mayer, Biochem., Zeitschr 3; Neuberg and Ascher, ibid., 6.
2
Ber. d. d. chem. Gesellsch., 34.
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