14 W. G. OVEREND AND M. STACEY 



tissues which he considered to be an ethyl riboside, but confirmation of this 

 discovery has not been reported. Very recently, however, it has been claimed 

 that the browning occurring in moist fish flesh on exposure to high tempera- 

 tures is due to reactions of the Maillard type^* and that the sugar contrib- 

 uting the aldehyde groups is D-ribose.'*^ 



2-Deoxy-D-ribose is the only 2-deoxypentose believed to occur in nucleic 

 acids. Chargaff and his co-workers^"- ^^ have examined by chromatographic 

 techniques a range of nucleic acids isolated from animal, plant and bac- 

 terial sources and have found no trace of any other deoxysugar. In nucleic 

 acids 2-deoxy-D-ribose is linked glycosidically to either a purine or py- 

 rimidine base. As is the case with ribose, the purine bases are adenine and 

 guanine. The pyrimidine bases found united to the deoxypentose are 

 cytosine and thymine (in ribonucleic acids uracil replaces this latter base) 

 and in some cases 5-methylcytosine in small amounts. Although not a 

 normal component of deoxypentose nucleic acids, the deoxyriboside of 

 uracil has been obtained from an enzymic hydrolysis of a commercial 

 sample of herring sperm deoxypentose nucleic acid.*- It is considered to 

 have been formed by an enzyme (cytosine deoxyriboside deaminase^^) 

 introduced into the digest by bacterial contamination. In these nucleosides, 

 2-deoxy-D-ribose is linked to position 9' of the purine bases or to position 

 3' of the pyrimidine bases. ^"^ There is no conclusive evidence concerning 

 the stereochemical disposition of the deoxyribose-base linkage, although 

 Furberg-^ considers that deoxyribonucleotides may have the same shape 

 as ribonucleotides, in which he demonstrated by X-ray analysis that the 

 linkage was of the /3-D-type. Hammarsten and colleagues*^ have presented 

 evidence from biochemical experiments which can be interpreted*® as 

 indicating a /3-D-configuration for the sugar-base linkage in deoxyribonucleo- 

 tides. Until recently, the lactol ring structure of 2-deoxy-D-ribose in nucleic 

 acid had been proved conclusively only for the thymidine nucleoside com- 

 ponent and in this case it was furanose in form." Subsequently Brown 

 and Lythgoe*^ by apphcation of the periodate oxidation procedure to the 



*8 H. L. A. Tarr, J. Fisheries Research Board Can. 8, 74 (1950). 



" H. L. A. Tarr, Nature 171, 344 (1953). 



^» E. Chargaflf, E. Vischer, R. Doniger, Charlotte Green, and F. Misani, J. Biol. 



Cheni. 177, 405 (1949). 

 " E. Chargaff and Rakoma Lipshitz, J. Am. Chem. Sac. 75, 3658 (1953). 

 " C. A. Dekker and A. R. Todd, Nature 166, 557 (1950). 



" T. P. Wang, H. Z. Sable, and J. O. Lampen, J. Biol. Chem. 184, 17 (1950). 

 " J. M. Gulland and L. F. Story, J. Chem. Soc. 1938, 259, 692. 

 " E. Hammarsten, P. Reichard, and E. Saluste, J. Biol. Chem. 183, 105 (1950). 

 56 J. Baddiley, Ann. Rev. Biochem. 20, 172 (1951). 



" P. A. Levene and R. S. Tipson, Science 81, 98 (1935); J. Biol. Chem. 109, 623 (1935). 

 w D. M. Brown and B. Lythgoe, /. Chem. Soc. 1950, 1990. 



