THE PROTEIN SUBSTANCES. IO1 



place, and one of these parts is a simple native protein sub- 

 stance and the other the nuclein or further and final decompo- 

 sition product, nuclcinic acid. The nucleo-proteids are there- 

 fore described as combinations of native albumins with 

 nucleinic acid. 



In breaking down the complex nucleo-proteid it appears that 

 several stages must be distinguished, the body described as a 

 " nuclein " containing still some native albumin. Finally, 

 however, the residue or characteristic part, the nucleinic acid, 

 is left. Although many investigations have been made there 

 is still much uncertainty about the nature of this acid. In- 

 deed, from different parent substances acids of somewhat dif- 

 ferent properties have been obtained, so that it is customary to 

 speak of the nucleinic acids. These will be considered below. 



Like the native proteins already described the nucleo-proteids 

 are coagulated by heat and by acids. They are soluble in 

 water, salt solutions and also in alkali solutions. By means of 

 large excess of salt they suffer precipitation. In the last few 

 years nucleo-proteids from different sources have been studied, 

 especially from yeast cells, the thyroid gland, the pancreas 

 and different kinds of spermatozoa. The sperm and sperma- 

 tozoa of sea urchins and fish have furnished a number of these 

 substances because of their relative richness in cell structures. 

 Thus characteristic products have been obtained from the sper- 

 matozoa of the salmon, the mackerel, the sturgeon and so on. 

 These appear to be distinct bodies, but more exact investiga- 

 tions may show that the apparent differences depend on foreign 

 proteins not completely separated in their preparation. 



Protamines and Histories. The simple native albumins 

 which exist in combination with nucleinic acids in the nucleo- 

 proteids are described by recent investigators as pro famines 

 and hisfones. In structure these bodies are probably the least 

 complex of all protein substances. They do not exist free in 

 nature but in combination with nucleinic acids, hematin or 

 other simple " prosthetic group." The protamines contain 

 no sulphur but are very rich in nitrogen and low in carbon 



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