Originally published in Arkiv for Kemi 24 A, 12. (1!)47). 



73. TURNOVER OF NUCLEIC ACID IN RETROGRADE 



SARCOMATA 



L. Ahlstrom, H. Euler, and G. Hevesy 

 From the Institute for Research in Organic Chemistry, Stockholm 



Desoxyribosenucleic acid is wholly or mainly confined to the cell 

 nuclei. That desoxyribosenucleic acid vanishes in certain phases of the 

 mitotic cycle and accumulates in others, was conspiciously shown by 

 Caspersson^ in making use of the technique of ultraviolet absorption. 

 We have, therefore, to expect an appreciable formation of "new" desoxy- 

 ribosenucleic acid molecules in mitotic cells. The ultraviolet absorption 

 method has the great adventage that it makes it possible to carry oul 

 micro-determinations //? situ. When applying the radioactive method, 

 we have to isolate the desoxyribosenucleic acid P from all other phos- 

 phorus fractions present. This requires the employment of substantial 

 quantities of tissues. The radioactive method has, however, 2 advent- 

 ages: 



(a) It indicates all new formation of the desoxyribosenucleic acid, 

 including any such formation which takes place without a perceptable 

 change in the total amount of desoxyribonucleic acid present. 



(b) The formation of small amounts of new desoxyribosenucleic acid 

 as correspond to only 0.1 percent, or even less of the total amount of 

 desoxyribonucleic acid present in the tissue sample under investigation, 

 can be determined. The unique sensitiveness of the radioactive method 

 is due to the fact, that the "old" molecules not being radioactive, are 

 not registered at all; and, correspondingly, if the number of molecules 

 increases during the experiment from 1000 to 1001, the radioactivity 

 of the sample increases from to 1. The result arrived at is thus in 

 contrast to all other methods, not based on a small difference between 

 two large figures. 



Former investigations into the percentage of new formation of des- 

 oxyribosenucleic acid in the growing Jensen sarcomata led to the result 

 that in the course of 2 hours about 2 out of 100 desoxyribosenucleic 

 acid molecules are newly formed. 



'i)Cf. T. Caspersson and L. Santesson, Acta Rad. Suppl. 17 (1942). 



