MACROMOLECULES 111 



B. The Nucleoproteins 



The nucleoproteins of the nuclei of trout, salmon and herring sperm, are 

 made up almost entirely of protamine and desoxyribonucleic acid. The 

 nucleoproteins of thymus are made up of desoxyribonucleic acid (40%), 

 ribonucleic acid (1-2%), histones and non-basic proteins. The cellular 

 nuclei contain chiefly desoxyribonucleic acid but, in addition, there is a 

 little ribonucleic acid (in the nucleolus and chromosomes). The cytoplas- 

 mic nucleoproteins in general contain only ribonucleic acid associated 

 with proteins which do not have the basic properties of those joined to 

 desoxyribonucleic acid. But the reproductive cell of animals (oocytes) 

 contain desoxyribonucleic acid in the cytoplasm. The desoxyribonucleic 

 acid of the chromosomes is combined with histones, protamines, and a 

 protein of the usual type, which is referred to as residual protein. 



Protamines not possessing primary amino groups are associated with 

 DNA by a salt linkage, and this is also the case for the histones. Separa- 

 tion takes place when an extraction is made with solutions of high ionic 

 strength. The protamines and histones are very heterogeneous. The 

 residual protein, unlike the histones, contains tryptophan. 



IV. METALLOPROTEINS 



The metalloprotein structure is one which is widely and diversely 

 employed in the chemistry of living cells. 



A. METALLOPROTEINS IN WHICH THE MeTAL IS BoUND TO THE PrOTEIN 



Through the Intermediary of Another Structure 



(a) Haemoproteins 



Iron possesses 26 electrons distributed among 4 shells (K, L, M, N). 

 The K and L shells are saturated and contain 2 and 8 electrons respectively, 

 all of which are paired ; the N shell contains 2 paired electrons ; the M shell 

 contains 14 electrons. The M shell has 1 5 orbital, 3 p orbitals and 5 d 

 orbitals; the energy level of the 5 orbital is below that of the ^ orbitals which 

 is less than that of the d orbitals. Each orbital can contain 0, 1 or 2 elec- 

 trons; in the last case the two electrons have opposite spins and their 

 magnetic effects cancel out (paired electrons). First of all, the electrons 



REFERENCES 



Bracket, J. (1952). Le role des acides nucleiques dans la vie de la cellule et de I'embryon, 

 Masson, Paris and Liege, Desoer, (Actualites biochimiques, No 16). 



Chargaff, E. & DAvmsoN, J. N. (1955). The Nucleic Acids. Chemistry and Biology. 

 2 vols. Academic Press, New York. (The collective effort of leading workers 

 in this field. This work contains full information and a constructive discussion 

 of the subject.) 



