02 D. SHUGAR 



in the presence of purine and pyrimidine derivatives and their suggestion 

 that this may be due to light activation of nucleotides. 



1. Carbohydrates 



The saturated carbon chains of carbohydrates would not be expected to 

 exhibit specific absorption in the region normally used for photobiological 

 studies and, in fact, it was shown many years ago that, following careful 

 purification, sugars possess only extremely low end absorption below 220 

 m/x at neutral pH. 103 



In view of the fact that extensive irradiation of nucleic acids, as well as 

 of some nucleotide coenzymes, leads to the destruction of the sugar moieties 

 (Sections V, 3 and VI, 1), it is pertinent to inquire to what extent this is 

 due to the direct effect of absorption of light. Theoretically, there should 

 be no such effect at wavelengths at least to the red of 220 m/x. 



There exist, nonetheless, scattered reports on the destruction of free 

 sugars and polysaccharides by ultraviolet irradiation. According to Holtz, 104 

 irradiated neutral glucose solutions are decomposed with the formation of 

 an oxidation-reduction system resembling that for ascorbic acid. In a more 

 extensive study Rice 105 found destruction of sugars in irradiated ribose, 

 glucose, cytidylic and adenylic acids as well as RNA and DNA. With the 

 exception of the nucleic acids there is little doubt that such results are due 

 to the use of sources with high emission at short wavelengths. For instance, 

 Hvidberg et al. m demonstrated that the viscosity of hyaluronate solutions 

 is destroyed by ultraviolet irradiation, the effective wavelengths being below 

 300 nixx; however, since the source used was a Phillips HP lamp with the 

 glass filtering envelope removed, the effective radiation must have been 

 well to the violet of 230 mix. 



In agreement with this is the observation of Laurent and Wertheim 107 

 that neutral solutions of various sugars are unaffected by exposure to a 

 source from which the shorter wavelengths were eliminated. Carter 108 has 

 found adenylic acid to be remarkably resistant to radiation from a battery 

 of germicidal lamps. The stability to irradiation of carbohydrate moieties 

 is further testified to by the high degree of reversibility prevailing for the 

 photoproducts of pyrimidine nucleosides and nucleotides (Section V, 4). 



In alkaline solution, on the other hand, irradiation of various sugars even 

 at 253.7 mxi, produces decomposition with formation of a variety of products 



103 L. Kwiecinski, J. Meyer, and L. Marchlewski, Z. physiol. Chem. 176, 292 (1928); 

 L. Marchlewski and W. Urbanczyk, Biochem. Z. 262, 248 (1933). 



104 P. Holtz, Arch, exptl. Pathol, u. Pharmakol. 182, 141 (1936). 



105 E. W. Rice, Science 115, 92 (1952). 



106 E. Hvidberg, S. A. Kvorning, A. Schmidt, and J. Schon, Nature 181, 1338 (1958). 



107 T. C. Laurent and E. Wertheim, Acta Chem. Scand. 6, 678 (1952). 



108 C. E. Carter, J. Am. Chem. Soc 72, 1835 (1950). 



