Hydrolysis of the proteins of maize, Zea Mays / by Thomas B. Osborne and S.H. Clapp.

  • Thomas Burr Osborne
Date:
[1908]
Catalogue details

Licence: In copyright

Credit: Hydrolysis of the proteins of maize, Zea Mays / by Thomas B. Osborne and S.H. Clapp. 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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    with cold 85 per cent (by volume) alcohol as long as anything was removed. The voluminous extract was filtered perfectly clear and concentrated under reduced pressure to a small volume. The clear syrup that remained, after cooling, was poured in a very fine stream into about eight volumes of distilled ice water, containing a very little sodium chloride in order to promote the separation of the zein. The zein, which separated as a flocculent precipitate, soon united to a coherent plastic mass. This was filtered out on cloth, washed superficially with water, and again dissolved in 95 per cent alcohol to a syrup. This solution was then shaken out repeatedly with petroleum benzine until all the yellow coloring matter was removed, together with most of the fat. The perfectly water-clear solution of the zein was then poured into eight volumes of cold water, containing a very little sodium chloride. The zein that separated was then dried and ground, yield- ing a fine powder that was entirely colorless. The meal that had been extracted with alcohol until nothing more could be obtained from it was then extracted with a large quantity of 0.20 per cent sodium hydroxide solution, the extract filtered per- fectly clear and treated with very dilute hydrochloric acid until the dissolved protein separated as a flocculent precipitate. This was then filtered out, again dissolved in the dilute sodium hydroxide solution, the resulting solution filtered perfectly clear, and the pro- tein precipitated as before. After washing with water, this precipi- tate was digested several successive times with fresh quantities of strong alcohol as long as any zein was removed, and when dehy- drated with absolute alcohol and dried, formed a dusty powder entirely free from color. This preparation represents the residual protein of the seed after all that is soluble in alcohol has been removed. Of its individuality as a.protein substance we of course know nothing, for it has hereto- fore been impossible to obtain any considerable quantity of it in a state of even approximate purity as respects admixture with non- protein substances. This preparation contains more nitrogen than the five other preparations that we have previously made, and prob- ably contains but a small amount of non-protein matter. As to whether it consists of a single protein substance or is a mixture, we can say nothing, for we have no evidence whatever on this point. We have, nevertheless, made this preparation for hydrolysis because it represents' a large part of the protein of the seed and it is im-
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