PROTEINS 115 



EXPERIMENTS ON METAPROTEINS 

 ACID METAPROTEIN (ACID ALBUMINATE) 



Preparation and Study. Take 25 grams of hashed lean beef washed free 

 from the major portion of blood and inorganic matter, and place it in a medium- 

 sized beaker with 100 c.c. of 0.2 per cent HC1. Place it on a boiling water-bath 

 for one-half hour, filter, cool, and divide the nitrate into two parts. Neutralize 

 the first part with dilute KOH solution, filter off the precipitate of acid metapro- 

 tein and make the following tests : 



(1) Solubility. Solubility in the ordinary solvents (see page 22). 



(2) Millon's Reaction. 



(3) Coagulation Test. Suspend a little of the metaprotein in water (neutral 

 solution) and heat to boiling for a few moments. Now add 1-2 drops of KOH 

 solution to the water and see if the metaprotein is still soluble hi dilute alkali. 

 What is the result and why? 



(4) Test for Unoxidized Sulphur (see page 107). v 



Subject the second part of the original solution to the following tests: 



(5) Coagulation Test. Heat some of the solution to boiling hi a test-tube. 

 Does it coagulate? 



(6) Biuret Test. 



(7) Influence of Protein Precipitants. Try a few protein precipitants such as 

 picric acid and mercuric chloride. How do the results obtained compare with 

 those from the experiments on egg albumin? (See page 102.) 



ALKALI METAPROTEIN (ALKALI ALBUMINATE) 



Preparation and Study. Carefully separate the white from the yolk of a 

 hen's egg and place the former in an evaporating dish. Add concentrated potas- 

 sium hydroxide solution, drop by drop, stirring continuously. The mass gradu- 

 ally thickens and finally assumes the consistency of jelly. This is solid alkali 

 metaprotein or "Lieberkiihn's jelly." Do not add an excess of potassium hydrox- 

 ide or the jelly will dissolve. Cut it into small pieces, place a cloth or wire gauze 

 over the dish, and by means of running water wash the pieces free from adherent 

 alkali. Now add a small amount of water, which forms a weak alkaline solution 

 with the alkali within the pieces, and dissolve the jelly by gentle heat. Cool the 

 solution and divide it into two parts. Proceed as follows with the first part: 

 Neutralize with dilute hydrochloric acid, noting the odor of the liberated hydro- 

 gen sulphide as the alkali metaprotein precipitates. Filter off the precipitate 

 and test as for acid metaprotein (tests i, 2, 3 and 4), above, noting particularly 

 the sulphur test. How does this test compare with that given by the acid meta- 

 protein? Make tests on the second part of the solution the same as for acid 

 metaprotein (tests 5, 6 and 7) above. 



Coagulated Proteins 



These derived proteins are produced from unaltered protein mate- 

 rials by heat, by long standing under alcohol, or by the continuous 

 movement of their solutions such as that produced by rapid stirring or 

 shaking. In particular instances, such as the formation of fibrin from 



