The vegetable proteins / by Thomas B. Osborne.

  • Thomas Burr Osborne
Date:
1909
Catalogue details

Licence: Public Domain Mark

Credit: The vegetable proteins / by Thomas B. Osborne. Source: Wellcome Collection.

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    in edestin, and it may be that in the formation of edestan a slight loss of nitrogen occurs. The difference, however, between these analyses is too slight to warrant a definite conclusion on this point. The edestan, thus prepared for analysis, is a voluminous white powder which swells somewhat in water and forms a colourless, trans¬ parent jelly with very dilute hydrochloric acid. In the dry state it is slightly, if at all, soluble in strong ammonia, but the gelatinous mass formed by treating the substance with very dilute hydrochloric acid is slightly soluble therein and yields a solution which gives a precipitate with ammonium chloride. Consequently when hydrochloric acid is added to its ammoniacal solution a precipitate forms, even when much of the ammonia is still unneutralised. The ammoniacal solution is not precipitated by sodium chloride. Edestan exists in preparations of edestin chloride in combination with acid. The amount of acid required to form a compound sparingly soluble in water appears to be definite, as the following experiments show. A quantity of edestan obtained from a preparation of edestin chloride was suspended in water and dialysed until free from chloride. The dialyser then contained an opalescent fluid and a voluminous precipitate. The acidity of the substance dissolved in this solution was found in two experiments to correspond to 2i-5 and 23*4 c.c. of a centinormal solution per gramme. Other experiments gave similar results, from which it appears that the acidity of the edestan chloride was almost exactly three times that of the edestin chloride insoluble in water or one and one-half times that of the edestin chloride soluble therein. From these results we may conclude that the basic property of this altered product is greater than that of the original protein, and as this substance originates so readily and in such large proportion in the presence of a small amount of free acid, it is evident that ex¬ periments which have been made to determine the acid-combining power of proteins, in which an excess of acid has been employed, do not necessarily show the acid-combining power of unchanged proteins. The reactions of edestan are similar to those which are considered to be characteristic of the histone group, but there is manifestly no connection between this substance and the true histones. The globin obtained from haemoglobin by the action of dilute acids is generally designated a histone on the ground of the similarity of the reactions of the two substances. It is possible, if not probable, that globin more nearly resembles edestan than the true histones and that it is a similar product of alteration of the protein constituent of the haemoglobin
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