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80 THE PROTEIN SUBSTANCES.
bacterial proteids, 1
are free from sulphur; some, such as gelatin and
elastin, are very poor in sulphur, while others, especially horn sub-
stances, are relatively rich in sulphur. On hydrolytic cleavage with
mineral acids, the sulphur of the protein substances is regularly, at
least in part, split off as cystine (K. Morner) or, with bodies poorer in
sulphur, as cysteine (Embden) , but this, according to Morner and Patten,
is a secondary formation. From certain protein substances a-thiolactic
acid (Suter, Friedmann, Frankel), which Morner claims is also pro-
duced secondarily, mercaptans and sulphureted hydrogen (Sieber and
Schoubenko, Rubner), and a body having the odor of ethyl sulphide
(Drechsel) have been obtained.2
A part of the sulphur separates as potassium or sodium sulphide on
boiling with caustic potash or soda, and may be detected by lead acetate
and quantitatively determined (Fleitmann, Danilewsky, Kruger,
Fr. Schulz, Osborne, K. Morner 3
). What remains can be detected
only after fusing with potassium nitrate and sodium carbonate and
testing for sulphates. The ratio between the sulphur split off by alkali
and that not split off is different in various proteins. No conclusions
can be drawn from this • in regard to the number of forms of combination
which the sulphur has in the protein molecule. As shown by K. Morner,
only about three-fourths of the sulphur in cystine can be split off by
alkali, and the same is true for the cystine-yielding complex of the pro-
tein substances. If the quantity of lead-blackening sulphur in a pro-
tein body be multiplied by f, we obtain the quantity corresponding to
the cystine sulphur in the body. By such calculation Morner found
in certain bodies, such as horn substance, seralbumin and serglobulin,
that the quantity of cystine sulphur and total sulphur were identical,
and therefore we have no reason for considering the sulphur in these
bodies as existing in more than one form of combination. In other
proteins, such as fibrinogen and ovalbumin, on the contrary, only one-
half or one-third of the sulphur appeared as cystine sulphur.
Just as in the products of acid hydrolysis of proteins we know of
two forms of oxygen bondage, the hydroxyl form OH and the carbonyl
1
See Nencki and Schaffer, Journ. f. prakt. Chem. (N. F.), 20, and M. Nencki, Ber.
d. d. chem. Gesellsch., 17.
2
K. Morner, Zeitschr. f. physiol. Chem., 28, 34, and 42; Patten, ibid., 39; Embden,
Urid., 32; Suter, ibid., 20; Friedmann, Hofmeister’s Beitriige, 3; Sieber and Schou-
benko, Archiv d. sciences biol. de St. Pdtersbourg, 1; Rubner, Arch. f. Hygiene, 19;
Drechsel, Centralbl. f. Physiol., 10, 529; Frankel, Sitzungsber. d. Wien. Akad., 112,
II b, 1903.
* Fleitmann, Annal. dor Chem. und Pharm., 6fi; Danilewsky, Zeitschr. f. physiol.
•Chem., 7; Kruger’s, Pflliger’s Archiv, 43; F. Schulz, Zeitschr. f. physiol. Chem., 25;
Osborne, Connecticut Agric. Expt. Station Report 1900; Morner, 1. c.
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