Pfizer Handbook of Microbial Metabolites 510 



of a helical coil of paired strands, the strands and coils 

 being associated by hydrogen bonding, e.g., between the 

 amino group of adenine and the carbonyl group of thy- 

 mine.^ This structure is supported by roentgen ray dif- 

 fraction data, by acid-base titration studies and by light- 

 scattering measurements on solutions. There are some 

 recent indications, however, that single-stranded DNA 

 does exist in some cases. 



Tobacco mosaic virus, a crystalline substance which 

 has been investigated extensively, consists of a single 

 strand of RNA coiled within a protein sheath. The de- 

 gree of organization (non-covalent bonding) in the nu- 

 cleic acid moieties of nucleoproteins has been studied. - 

 In some instances the nucleic acids seem to be less organ- 

 ized in the intact protein than in the free state. 



Pyrimidine nucleotides also serve as coenzymes in a 

 number of biological reactions. Thus uridine nucleotide 

 is important in the enzymic manipulation of sugars. In 

 recent years, uridine-5'-diphosphate sugar esters have 

 been isolated from a variety of animal, plant and mi- 

 crobial sources. 



Confining our attention to microorganisms, uridine di- 

 phosphate glucose, UDP-galactose, UDP-acetylglucosa- 

 mine as well as uridine triphosphate (UTP) and uridine- 

 diphosphate (UDP) have been isolated from yeast. ^' * •'' 

 The same substances have been isolated from Peiiicillium 

 chrysogenum mycelium." Other free nucleotides identi- 

 fied from the mold were: diphosphophyridine nucleotide 

 (DPN), cytidine-5'-monophosphate (CMP), adenosine-5'- 

 monophosphate (AMP), triphosphopyridine nucleotide 

 (TPN), guanosine-5'-monophosphate (CMP), inosine-5'- 

 monophosphate (IMP), uridine-5'-monophosphate (UMP), 



1 J. D. Watson and F. H. C. Crick, Nature 171 737, 964 (1953). 



- F. Bonhoeffer and H. K. Schachman, Biochem. and Biophys. Res. 

 Comms. 2 366 (1960). 



• R. Caputto, Luis F. Leloir, C. E. Cardini and A. C. Paladinl, 

 J. Biol. Chem. 184 333 (1950); E. Cabib, Luis F. Leloir and C. E. 

 Cardini, ibid. 203 1055 (1953). 



■' S. H. Lipton, S. A. Morell, Alexander Frleden and Robert M. Bock, 

 ;. Am. Chem. Soc. 75 5449 (1953). 



•^Hanns Schmitz, Biochem. Z. 325 555 (1954). 



'• A. Ballio, C. Casinovi and G. Serlupi-Crescenzi, Biochim. et 

 Biophys. Acta 20 414 (1956). 



