THE INDIVIDUAL GROUPS OF PROTEINS 433 



Properties. 



The protamines in the free state have not been much investigated '* 

 they are strong bases, blueing litmus, and absorb carbon dioxide from the 

 air. They are easily soluble in water, but insoluble in alcohol and ether. 

 They are not coagulated by heating, do not diffuse, give the biuret reaction, 

 sometimes other colour reactions and are laevorotatory. 



They form salts with acids of which the sulphate is the principal. The 

 chlorides are'more easily soluble, as also the carbonates and nitrates. They 

 form insoluble double salts with platinum chloride and mercuric chloride. 



They dissolve copper hydroxide giving solutions of a violet colour. 



They are precipitated by alkaloidal reagents in neutral or faintly alkaline 

 solution and are precipitated from solution by salts. They give precipi- 

 tates with other proteins, excepting the secondary proteoses, peptones and 

 polypeptides. 



They are precipitated from solution by a solution of sodium nucleate as 

 protamine nucleate. 



They contain 25-30 per cent, of nitrogen in their molecule, no sulphur 

 and no phosphorus. 



HISTONES. 



The group of proteins termed histones was established by Kossel, who 

 isolated a histone from the red blood corpuscles of the goose. Other members 

 of the group have since been isolated from the unripe testicles of fish and 

 from the thymus. During maturing of the sperm the histone in some cases 

 remains unchanged, but in other cases changes into protamine. 



Preparation. 



(1) From Unripe Fish Sperm. 



The material is first treated as in the preparation of protamines, but it is 

 extracted with dilute hydrochloric acid. The extract is saturated with sodium 

 chloride, the precipitate is freed from salt by dialysis and the solution preci- 

 pitated by ammonia. 



(2) From Red Blood Corpuscles. 



The paste of corpuscles is treated with water and ether ; the insoluble 

 residue after washing with water is extracted with dilute hydrochloric acid. The 

 solution is saturated with sodium chloride and the precipitate is freed from salt 

 by dialysis. The histone is then precipitated by adding ammonia. 



(3) From Thymus Nucleohistone (p. 466). 



The nucleohistone is treated with o'8 per cent, hydrochloric acid and the 

 solution is precipitated with ammonia. 



Thymus histone is also formed when solutions of nucleohistone are saturated 

 with salt. The histone is precipitated on adding ammonia. 



