Practical physiological chemistry : a book designed for use in courses in practical physiological chemistry in schools of medicine and of science . t is the mother-substance of cadaverin and has Fig. 33. Lysin Picrate. never been obtained in crystalline form. The picrate of lysinmay be crystallized, however; the crystals of this body, ob-tained from the proteid legumin, are shown in Fig. 33. Arginin, C6H14N402.—Arginin is the most widely dis-tributed of the decomposition products of the proteids. I )!•:(?( rnsi I lo\ IKODUCTS OF PROTEIDS. 79 Every proteid so far subjected to decomposition
Practical physiological chemistry : a book designed for use in courses in practical physiological chemistry in schools of medicine and of science . t is the mother-substance of cadaverin and has Fig. 33. Lysin Picrate. never been obtained in crystalline form. The picrate of lysinmay be crystallized, however; the crystals of this body, ob-tained from the proteid legumin, are shown in Fig. 33. Arginin, C6H14N402.—Arginin is the most widely dis-tributed of the decomposition products of the proteids. I )!•:(?( rnsi I lo\ IKODUCTS OF PROTEIDS. 79 Every proteid so far subjected to decomposition lias yielded thisbody among the products. Because of this fact, some investi-gators consider arginin to be the nucleus of the proteid mole-cule. Chemically, arginin is guanidin-a-amino-valerianic acidand possesses the following structural formula: II II H Nil I I I INH-C-C-C-C-COOH. I I I I I NH = C II H H H INH2 It is claimed that in the ordinary metabolic activities of theanimal body arginin gives rise to urea. Histidin, C6H9N302.—This body occurs most abundantlyas a decomposition product of globin, the proteid constituent Fig. Histiimx Hydrochloride. of haemoglobin. The free base is laevorotatory, whereas thesalts of histidin are dextro-rotatory. Histidin is now believed 80 PHYSIOLOGICAL CHEMISTRY. to be a-anrino-fi-imido-asol-propionic acid with the following structural formula: H NHo I IHC = C-C-C-COOH. I IH H N\/NH CH Crystals of histidin ltydrochloride are shown in Fig. 34, p. 79. the ordinary courses in physiological chemistry pre-clude any extended study of the decomposition products ofproteids, the manipulation of a simple decomposition and thesubsequent isolation and study of a few of the products mosteasily and quickly obtained will not be without interest. Tothis end the student may use the following decomposition pro-cedure : Treat the proteid in a large flask with water contain-ing 3-5 per cent of H2S04 and place it on a water-bath un
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