138 J. BADDILEY 



k. Deoxyribose Nucleotides 171 



1. Deoxynucleoside Diphosphates 172 



3. Synthesis of Nucleotides 172 



a. The 5'-Phosphates 173 



b. The a and b Isomers 174 



c. The Cyclic Phosphates 174 



d. Deoxyribose Nucleotides 175 



e. Miscellaneous 176 



4. Properties of Nucleotides 177 



5. Nucleotide Coenzymes 177 



a. Adenosine Di- and Triphosphates (ADP and ATP) 179 



b. Di- and Triphosphopyridine Nucleotides (DPN and TPN) 181 



c. Flavin Adenine Dinucleotide (FAD) 183 



d. Coenzyme A (CoA) 184 



e. Uridine Diphosphate Glucose (UDPG) 186 



III. Addendum 188 



I. Nucleosides 

 1. Introduction 



In most living cells pyrimidines and purines are found in fairly large 

 amounts. [Cf. Bendich, Chapter 3.] Occasionally they occur in the free state, 

 e.g., theophylline, theobromine, caffeine, etc.; but those which predominate 

 in normal cells are usually present as glycosides. Purine and pyrimidine 

 glycosides are known as nucleosides. The nucleosides may be present as such 

 in cells but are found for the most part as their phosphoric esters, the nu- 

 cleotides, which play a vital role in all cells as coenzymes and, in a highly 

 polymerized condition, as nucleic acids. The term "nucleoside" has been 

 used in two senses. It has been considered as applying only to those pyrim- 

 idine and purine glycosides which are formed by hvdrolysis of nucleic acids, 

 but it is often used more generally for all naturally occurring pyrimidine 

 and purine glycosides. Nucleosides are, with very few exceptions, either |S-d- 

 ribofuranosides or D-2-deoxyribofuranosides. They are generally formed by 

 hydrolysis of nucleic acids with alkaline reagents and may be separated from 

 each other by methods described in Chapters 5 to 8. 



The first nucleoside to be isolated was called vernine' and renamed 

 guanosine (I) later. It is found together with adenosine^ (II) in alkaline 

 hydrolysates of ribonucleic acid. These two substances are believed to rep- 

 resent the entire purine nucleoside components of ribonucleic acids from 

 different sources. 



The pyrimidine nucleosides occurring in robonucleic acid are uridine (III) 

 and cytidine (IV). They are the 3-|S-D-ribofuranosides of uracil and cytosine, 

 respectively. 



1 E. Schulze and E. Bosshard, Z. physiol. Chem. 9, 420 (1885); 10, 80 (1885). 

 « P. A. Levene and W. A. Jacobs, Ber. 42, 2703 (1909). 



