158 NUCLEOPROTEINS, NUCLEIC ACIDS, RELATED SUBSTANCES 



of one ribose to phosphoric acid and a second linkage of this to carbon-3' 

 of the next nucleotide Such an arrangement for three ribonucleotides 

 can be represented as follows: 



O 



II 



Adenine-ribose 



(3') 



(2') 



Cytosine-ribose 



(2') 



Guanine-ribose • 



0— P— OH 



■oJ 



O 



II 

 ■0— P— OH 



_l 



■0 







■0— P— OH 

 ■0^ 



I — 



etc. 



The numbers 2' and 3' denote the carbon atoms in the ribose to which 

 the phosphoric acid group is linked. y 



Obviously, there are other ways of joining the guanine nucleotide to 

 the other two ribonucleotides. For example, the ribose part of the 

 guanine nucleotide could be linked to the adenine nucleotide, instead of 

 to the phosphoric acid in the cytosine nucleotide. The result would be 

 a triester structure, instead of the diester form given by the first type 

 of combination. The number of possibilities would increase as the 

 number of nucleotides joined together became larger. A more complicated 

 branching structure would be the result. There is no information as 

 to the sequence of the nucleotides in the nucleic acid structure. 



In the desoxynucleotides, carbon-2' of the sugar can not serve as a 

 point of linkage because it has no hydroxyl group. It is generally assumed 

 that the desoxynucleotides are joined together by way of carbons-3' and 

 5' of their respective sugars. 



Substances related to nucleosides and nucleotides 



Adenosine Phosphates. A nucleotide with the phosphoric acid at car- 

 bon-5' of the ribose, instead of at carbon-3', is the well-known muscle- 

 adenylic acid. It is also called adenosine monophosphate (AMP). 



N=C-NH, 



EC C-N 



-C-l/- 



CH 



0- 



HO OH 



H 



O 







O 



- C-C-C-C-C-0-P-O-P-O-P-OH 

 H H H H H I 



(1') (2') (3') (4') (5') OH 



Adenosine monophosphate - 



Adenosine diphosphate 



Adenosine triphosphate 



OH 



OH 



