PROTEINS. 



globulins become insoluble upon repeated reprecipitation and it may 

 possibly be found that the greater number of the proteans are 

 transformed globulins. Osborne, however, believes that nearly all 

 proteins may give rise to proteans. This investigator who has so 

 very thoroughly investigated many of the vegetable proteins claims 

 that the hydrogen ion is the active agent in the transformation. 

 The protein produced from the transformation of edestin is called 

 edestan, that produced from myosin is called myosan, etc. The 

 name protean was first given to this class of proteins by Osborne 

 in 1900 in connection with his studies of edestin. 



EXPERIMENTS ON PROTEANS. 



Preparation and Study of Edestan. Prepare edestin accord- 

 ing to the directions given on page 103. Bring the edestin into solu- 

 tion in 0.2 per cent hydrochloric acid and permit the acid solution 

 to stand for about one-half hour. 1 Neutralize, with a 0.5 per cent 

 solution of sodium carbonate, filter off the precipitate of edestan 

 and make the following tests: 



1. Solubility. Try the solubility in the ordinary solvents (see 

 page 23). Note the altered solubility of the edestan as compared 

 with that of edestin (see page 103). 



2. Millon's Reaction. 



3. Coagulation Test. Place a small amount of the protean in 

 a test-tube, add a little water and boil. Now add dilute hydro- 

 chloric acid and note that the protein no longer dissolves. It has 

 been coagulated. 



4. Tests on Edestan Solution. Dissolve the remainder of the 

 edestan precipitate in 0.2 per cent hydrochloric acid and make the 

 following tests : 



(a) Biuret Test. 



(b) Influence of Protein Precipitants. Try a few protein 

 precipitants such as picric acid and mercuric chloride. 



METAPROTEINS. 



The metaproteins are formed from the native simple proteins 

 through an action similar to that by which proteans are formed. 

 In the case of the metaproteins, however, the changes in the origi- 

 nal protein molecule are more profound. These derived proteins 

 are characterized by being soluble in very weak acids and alkalis, 



x The edestan solution preserved from experiment (5), page 104, may be used. 



