On certain proteid and albuminoid reactions and their significance / by J.W. Pickering.
- Pickering, John William.
- Date:
- 1893
Licence: Public Domain Mark
Credit: On certain proteid and albuminoid reactions and their significance / by J.W. Pickering. Source: Wellcome Collection.
Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.
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![of oxynitro, tri-nitro, hexanitro, and hexamidoalbumin sulphonic acid. From the above observations I conclude that the proteid in per- ■ fonniiig the xanthoproteic test has become so altered that to term it a nitroalbumin etc. is a misnomer. i Salk owski* has shewn that those products of the putrefaction of proteids which are allied to indole and phenol give the xanthoproteic j reaction. j The following bodies I find to give the reaction, salicylic acid, salicyl- j sulphonic acid, phenol, cholesterin, cholalic acid, taurocholalic acid. The j last three bodies evolve nitrous fumes when heated with nitric acid. ] The following bodies yield negative results, glycollic acid, creatine, J xanthin, hypoxanthine, all giving pale green solutions, skatol and hydro- \ cyanic acid a pale yellow solution, phenyl-acetic gives a colourless | solution, while allantoin, biuret and benzoic acid give greenish-yellow ^ colourations. r Pure leucine gives a negative reaction but this body often contains f tyrosine as an impurity when the reaction is given in a marked manner. ^ Cyanuric acid gives the yellow on boiling with nitric acid but the 4 yellow remains iinchanged on addition of ammonia. P3Togallol also ^ gives the yellow with boiling nitric acid but forms a brown solution on \ addition of ammonia, shewing that the introduction of a second hydroxyl ‘ group into the benzene nucleus prevents the reaction. Indole gives ■ a yellow with hot nitric acid but on addition of ammonia the solution becomes rose-red which changes on excess of ammonia back to a yellow. ■ From the above observations it will be noticed that those bodies which have a benzene nucleus with one hydrogen substituted by hydroxyl give the xanthoproteic reaction and that those bodies which contain a benzene nucleus without the hydroxyl as in phenyl-acetic, and benzoic acids do not give the reaction. Hence it is not improbable that the xanthoproteic reaction of proteids and cholalic acid de- pends on the existence of an hydroxybenzene nucleus. VII. The Sulphomolybdic Reaction. Frbhde* found that a solid proteid when heated with sulphuric and molybdic acids gives a brilliant blue precipitate. I have noted that the blue precipitate forms on heating a brilliant green solution. The pre- cipitate is also soluble in ammonia and deposits a white crystalline 1 Salkowski. Zeit. fiir physiol. Chem. xii. p. 215. ■' Frohde. Annalen der Chem. ii. Pharm. Vol. cxlv. p. 376. , I I I](https://iiif.wellcomecollection.org/image/b22396548_0030.jp2/full/800%2C/0/default.jpg)
