THE INDIVIDUAL GROUPS OF PROTEINS 471 



Tendomucoid. 



The tendon (Achilles tendon) is treated with -9 per cent, sodium chloride 

 solution and washed with water. It is then extracted with dilute lime water 

 and this solution is precipitated with acetic or hydrochloric acid. The pre- 

 cipitate is dissolved in lime water and again thrown out with acid. It is 

 washed with water, alcohol and ether. 



Tendomucoid forms a nearly white solid, which is insoluble in -i-*2 

 per cent, hydrochloric acid; it -is insoluble in water, but soluble in dilute 

 alkali. When digested with pepsin it yields chondroitin sulphuric acid. 



Osseomucoid. 



Bones are decalcified by treatment with -2-'4 per cent, hydrochloric 

 acid. The decalcified material is treated with half-saturated lime water and 

 the alkaline solution is acidified with hydrochloric acid (to -2 per cent.). The 

 precipitate of osseomucoid is washed with acidulated water and pure water, 

 redissolved and reprecipitated. 



Osseomucoid forms a colourless or faintly yellow coloured powder of acid 

 reaction. It dissolves in dilute alkali and alkali carbonate and in 5 per cent. 

 salt solution. From its solution in alkali it is precipitated by acid. 



It yields an acid similar to chondroitin sulphuric acid by digestion with 

 pepsin. 



Amyloid. 



Amyloid occurs -under pathological conditions in brain and nervous 

 tissue, in the liver, spleen, kidneys as fine concentric granules, or as glassy 

 deposits. Such tissues give with iodine a red-brown to violet colour, a violet 

 or blue colour with iodine and sulphuric acid, a reddish colour on treatment 

 with methyl violet followed by acetic acid. It has been isolated by 

 mechanical means and it forms homogeneous, circular or elliptical, granules 

 which on drying yield a yellow or brown powder. 



It is insoluble in water, weak acids and weak alkalies; it gives the 

 general protein reactions. It is changed by contact with alkalies or by 

 peptic digestion into such a form that the iodine and sulphuric acid reaction 

 is no longer positive. It seems to contain chondroitin sulphuric acid. 



Ovomucoid. 



White of egg is diluted with water and poured into boiling water faintly 

 acidified with acetic acid to coagulate the albumin. The filtrate is evaporated 

 down to a small volume and poured into alcohol. The ovomucoid is pre- 

 cipitated. Ovomucoid may also be obtained by saturating the solution 

 with ammonium sulphate. The precipitate is dissolved in warm water and 

 precipitated with alcohol. It is washed with alcohol and ether and dried. 

 Ovomucoid forms a colourless amorphous powder soluble in cold water. 

 The aqueous solution on evaporation leaves a horny, transparent residue, 

 insoluble in cold water, but soluble in hot water. The aqueous solution is 

 not precipitated by acetic acid. 



Solutions of ovomucoid are not precipitated by mercuric chloride, but they 

 are precipitated by tannic acid and phosphotungstic acid in acid solution. 



On boiling with acid, glucosamine is formed, as can be shown by heating 

 10 c.c. of a solution with an equal volume of concentrated hydrochloric acid for 

 5 minutes, cooling, neutralising and testing with Fehling's solution ; the cuprous 

 oxide is generally seen after the solution has stood so as to allow it to settle. 



Serum Mucoid. 



A glucoprotein very similar to ovomucoid is present in serum and it is pre- 

 pared in the same way by pouring 200 c.c. of serum or defihrinated blood into 

 1000 c.c. of boiling water containing 20 c.c. of 2 per cent, acetic acid. The fil- 

 trate from the coagulated proteins is evaporated and poured into alcohol. It may 

 also be prepared from the solution when the proteins are coagulated by alcohol. 



Urinary Mucoid. 



This glucoprotein is contained in the nubecolae of the urine. It is 

 soluble in dilute ammonia and is precipitated by acetic acid ; the precipitate 

 is soluble in excess of acetic and other acids. It closely resembles ovomucoid 

 in many of its properties. 



