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-iodotyrosine) 

 has been isolated. 



By the oxidation of protein by means of potassium permanganate, MALY 

 obtained an acid, oxyprotosulphonic acid, C 51.21, H 6.89, N 14.59 S 1.77, 23.24 

 per cent, which is not a cleavage product, but an oxidation product in which 

 the group SH is changed into SOi.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 oxy protein 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 2 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 desamino- 

 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-amicie-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 NEUBERG 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. (N. 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 Beitrage, 3; C. H. L. Schmidt, Zeitschr. f. physiol. Chem., 35, 36, 37; 

 Neuberg, Biochem. Zeitschr., 6: Pauly and Gundermann, Ber. d. d. chem. Gesellsch., 

 41, 43; Krzemecki, Chem. Centralbl., 1912; Pauly, Zeitschr. f. physiol. Chem., 76. 



2 Maly, Sitzungsber, d. k. Akad. d. Wissensch., 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. Fiirth, Hof- 

 meister's Beitrage, 6. 



3 Lessen, Annal. d. Chem. u. Pharm., 201; Kutscher, Zeitschr. f. physiol. Chem., 

 32; Zickgraf, ibid., 41; Seemann, ibid., 44; Kutscher and Schenck, Ber. d. d. chem. 

 Gesellsch., 37 and 38. 



