Chapter 6 



NUCLEOPROTEINS, NUCLEIC ACIDS 

 AND RELATED SUBSTANCES 



Introduction 



As already stated in the previous chapter, nucleoproteins are conjugated 

 proteins having nucleic acids as prosthetic groups. The literature on 

 nucleoproteins and nucleic acids is extensive and increasing at a rapid rate. 

 Hundreds of papers and more than a dozen reviews dealing with various 

 phases of the subject have appeared in the last five years. The great 

 activity in this field can be attributed to the widespread occurrence, in- 

 triguing chemical nature, and metabolic importance of these substances. 



One compelling reason for the attention being given to nucleoproteins 

 and nucleic acids is a growing belief that these compounds are closely 

 associated with the reproductive processes and may furnish the physical 

 basis of heredity. Chromosomes, the constituents of cells carrying the 

 hereditary characters, or genes, are largely, if not wholly, nucleoproteins. 

 Whatever chemical compounds' make up the genes, it is obvious that such 

 compounds must be sufficiently diverse in character to permit the almost 

 infinite number of combinations that occur in nature. In the nucleic 

 acids there is adequate diversification to meet this requirement. 



NUCLEOPROTEINS 



The term nucleoprotein arose because nucleic acids and the associated 

 protein, protamine, were first obtained from the highly nucleated material 

 of pus cells and fish sperm. Other nuclear cells such as thymus, liver, 

 spleen, and yeast are rich in nucleoproteins, but some nonnuclear cells, 

 for example, red blood corpuscles, also are a good source of nucleoprotein. 

 In fish sperm cells nucleoprotein makes up 50-80 per cent of the solid 

 material and over 90 per cent of the defatted nucleus. In the cell sap 

 of tobacco plants infected with virus, the nucleoprotein which makes up 

 the virus may amount to 2 g. per liter of sap. In yeast cells the nucleo- 

 protein amounts to only about 0.15 per cent of the dry matter. Bacteria 

 are much higher than yeast in nucleoproteins, e.g., 2-3 per cent of the dry 

 matter in Escherichia coli cells, 



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