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156 THE PROTEIN SUBSTANCES.
Tryptophane was first prepared in a pure form by Hopkins and
Cole,1
and they considered it as skatolaminoacetic acid. After Ellin-
ger showed that skatolcarbonic acid (Salkowski) and skatolacetic
acid (Nencki) were indolacetic acid and indolpropionic acid respectively,
and after the synthesis of d-Z-tryptophane by Ellinger and Flamand,2
the nature of this substance as indolaminopropionic acid was established.
By condensation of /3-indolaldehyde with hippuric acid Ellinger and Flamand
prepared the azlactone (lactimide)
:
N
CsHeNCHO+^Qg
6 6
=C8 H6N.CH ; C C .C 6H5 +2H20.
CO—
O
On boiling with dilute caustic soda, with the taking up of water, the sodium
salt of indoxyl-a-benzoylaminoacrylic acid,
C8H6 N.CH : C.NH.COCeH,
COONa
is obtained, from which by reduction and splitting off of the benzoyl group by
the action of sodium alcoholate the tryptophane is obtained
:
C8H6N.CH : C.NH.COC6H5
|
+H2 +H2 =C8 H6 N.CH2 .CH.NH2 +C6H5COOH.
COOH COOH
The trytophane formed in digestion is /-tryptophane, which is lsevoro-
tatory in aqueous solution (Hopkins and Cole). Racemic ^-trypto-
phane has also been obtained by digestion in certain cases by Allers
and Neuberg, this is probably formed from the /-tryptophane (Abder-
halden and L. Baumann 3
), which very readily undergoes racemization.
Tryptophane crystallizes in silky rhombic or six-sided leaves. It
does not have a sharp melting-point, and according to the rapidity of heat-
ing melts at 252°, 273° and 289°, according to various authorities.
Tryptophane is readily soluble in hot water, difficultly soluble in cold
water, and* only slightly soluble in alcohol. The solution of d-Z-trypto-
phane has a faintly sweetish taste, and /-tryptophane a faintly bitter taste.
The statements as to the optical behavior of tryptophane differ some-
what, which, according to Abderhalden, is probably due to the readiness
with which it undergoes racemization. According to Abderhalden
and L. Baumann,4
at 20° C. the aqueous solution has a rotation of
1
Journ. of Physiol., 27.
2
Ellinger, Ber. d. d. Chem. Gesellsch., 37 and 38. With Flamand, ibid., 40, and
Zeitschr. f. physiol. Chem., 55.
3
R. Allers, Biochem. Zeitschr., 6; C. Neuberg, ibid., 6; Abderhalden and Baumann,
Zeitschr. f. physiol. Chem., 55. (Literature on the specific rotation.)
* See Abderhalden and Baumann, Zeitschr. f. physiol. Chem., 55 (literature).
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