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GLYCOCOLL. 139
3. The Amino-acids. 1
CH2 (NH2 ) , „ , ,
Glycocoll (amino-acetic acid), Cl>H5N ( >2 = /, __ , also called gly-
COOH
cine or gelatin sugar, is found in the muscles of the invertebrates,
but has chief interest as a hydrolytic decomposition product of protein
bodies, especially fibroin, spider-silk elastin, gelatin, and spongin, as
well as of hippuric acid and glycocholic acid.
Glycocoll forms colorless, often large, hard rhombic crystals or four-
sided prisms. The crystals have a sweet taste and dissolve readily in
cold water (4.3 parts). Glycocoll is insoluble in alcohol and ether and
dissolves with difficulty in warm alcohol. Like the amino-acids in gen-
eral it combines with acids and alkalies. With the latter compounds
we must mention those with copper and silver. Glycocoll dissolves
cudHc hydroxide in alkaline liquids, but does not reduce at boiling heat.
A boiling-hot solution of glycocoll dissolves freshly precipitated cupric
hydroxide, forming a blue solution, which in proper concentration deposits
blue needles of copper-glyeocoll on cooling. The compound with hydro-
chloric acid is readily soluble in water but less soluble in alcohol.
Sorensen 2 finds that phosphotungstic acid does not precipitate
glycocoll from dilute solutions but only from concentrated ones. By the
action of gaseous HC1 upon glycocoll in absolute alcohol, beautiful
crystals are obtained of the hydrochloride of glycocoll-ethyl ester, which
melts at 144° C. and from which the glycocoll-ethyl ester can be obtained
by the method suggested by E. Fischer 3
for the separation of glycocoll
from the other amino-acids. On shaking with benzoyl chloride and
caustic soda, hippuric acid is formed, and this is also made use of in
different ways in detecting and isolating glycocoll (Ch. Fischer, Gox-
nermaxn, Spiro 4
). The /3-naphthalene-sulpho-glycine with a melt-
ing-point of 159°, the 4-nitro-tolulene-2-sulpho-glycine, melting at 180°,
and the a-naphthylisocyanate compound melting at 190.5-191.5° are
also of importance. On putrefaction methane is probably produced
from glycocoll.
Glycocoll can be best prepared from hippuric acid by boiling it with
4 parts dilute sulphuric acid (1:6) for ten to twelve hours. After cooling
1
In regard to the division of the amino-acids among the three chief groups of
organic compounds we refer to pages 85-86.
2
Meddelelser, fraa Carlsberg-laboratoriet, 6, 1905.
3
Ber, d. d. chem. Gesellsch., 34.
4
Ch. Fischer, Zeitschr. f. physiol. Chem., 19; Spiro, ibid., 28; Gonnermann,
Pfliiger’s Arch., 59.
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