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OXIDATION OF PROTEINS. 83
aromatic nucleus of tyrosine and also perhaps in the indol nucleus of
tryptophane and the imidazol nucleus of histidine.1
Halogen proteins
occur, as will be shown later, in the animal kingdom, especially in the
albuminoid group and indeed iodized tyrosine (3-5 di-iodotyro-incj
has been isolated.
By the oxidation of protein by means of potassium permanganate, Maly
obtained an acid, ojcyprotosulphonic acid, C 51.21, H 6.89, X 14.59 8 1.77, O 23.21
per cent, which is not a cleavage product, but an oxidation product in which
the group SH is changed into SO;.OH. This acid does not give the proper color
reaction with Millon’s reagent, yields no tyrosine or indol, but gives benzene
on fusing with alkali. On continued oxidation Maly obtained another acid,
peroxyproteic acid, which gives the biuret reaction, but is not precipitated by
most protein precipitants. The oxyprotein obtained by Schulz on the oxida-
tion of protein by hydrogen peroxide is closely related to oxyprotosulphonic
acid in composition and general characteristics, but contains lead-blackening
sulphur and gives Millon’s reaction. The oxyprotein is claimed to be a pure
oxidation product, while in the production of oxyprotosulphonic acid Schulz
claims that a cleavage takes place. According to Buraczewski and Krauze
the oxyprotosulphonic acid is a mixture of several substances. According to
the investigations of v. Furth - there exist at least three different peroxyproteic
acids (from casein) which differ from each other by a different division of the
nitrogen in the molecule. On treatment with baryta-water we find that they
split off basic complexes and oxalic-acid groups, and new bodies, the dcsamino-
proteic acids, which give the biuret reaction, are produced. These later acids, which
on hydrolysis give benzoic acid but no diamino-acids, may be further oxidized,
which is not true of the peroxyproteic acids, and yield a new group of acids, the
kyroproteic acids, which give the biuret reaction, hold about one-half of their
nitrogen (11.08 per cent total nitrogen) in acid-aniide-like combination, but
yield neither basic products nor benzoic acid.
On the oxidation of gelatin or protein with permanganate we also obtain
oxaminic acid, oxamide, oxalic acid, oxaluric-acid amide, succinic acid, several
volatile fatty acids, and guanidine, which was first shown by Lossen as an oxida-
tion product. 3
On the oxidation of gelatin by ferrous sulphate and hydrogen peroxide
Blumenthal and Xeuberg have obtained acetone as a product, and Orgler
the same from ovalbumin. The action of ozone upon casein has been studied
1
In regard to the action of halogens upon proteins see Loew, Journ. f. prakt.
Chem. (N. F.), 31; Blum, Munch, med. Wochenschr., 1896; Blum and Vaubel, Journ.
f. prakt. Chem. (X. F.), 57; Liebrecht, Ber. d. deutsch. chem. Gesellsch., 30; Hop-
kins and Brook, Journ. of Physiol., 22; Hopkins and Pinkus, Ber. d. deutsch. chem.
Gesellsch., 31; Hofmeister, Zeitschr. f. physiol. Chem., 24; Kurajeff, ibid., 26; Oswald,
Hofmeister’s Beitriige, 3; C. H. L. Schmidt, Zeitschr. f. physiol. Chem., 35, 36, 3";
Xeuberg, Biochem. Zeitschr., 6: Pauly and Gundermann, Ber. d. d. chem. Gesellsch.,
41, 43; Krzemecki, Chem. Centralbl., 1912; Pauly, Zeitschr. f. physiol. Chem., "6.
’ Maly, Sitzungsber, d. k. Akad. d. Wissenseh., Wien, 91 and 97. Also Monatshefte
f. Chem., 6 and 9. See also Bondzynski and Zoja, Zeitschr. f. physiol. Chem., 19;
Bernert, ibid., 26; Schulz, ibid,, 29; Buraczewski and Krauze, ibid, 76; v. Furth, Hof-
meister’s Beitriige, 6.
3
Lessen, Annal. d. Chem. u. Pharm., 201; Kutscher, Zeitschr. f. physiol. Chem.,
32; Zicksraf, ibid., 41; Seemann, ibid., 44; Kutscher and Schenck, Ber. d. d. chem.
Gesellsch.. 37 and 38.
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