Originally published in Nature, 140, 725 (1937) 



95. PHOSPHORUS EXCHANGE IN YEAST 



G. Hevesy, K. Lindeestr0m-Lang and N. Nielsen 



From the Institute for Theoretical Physics and the Carlsberg Laboratory of 



Copenhagen 



The individual phosphorus atoms present in the leaves of plants have 

 been found^-^^ for the most part to exchange with great ease within a short 

 time. We extended our experiments to the behaviour of phosphorus 

 atoms present in yeast. 



Yeast was grown in a culture solution which, after the lapse of some 

 days, was replaced by a similar solution containing 8.7 mgm of labelled 

 phosphorus per 100 cm^, besides the usual amount of salts and in some 

 cases ten per cent sugar, in others none. The radioactivity of the labelled 

 sodium phosphate was such that 1 mgm P corresponded to 1000 activity 

 units. After the yeast had grown for twenty-four hours in the solution 

 containing labelled phosphorus, it was removed, washed carefully and 

 digested by treatment with sulphuric acid and nitric acid. The phos- 

 phorus content of the solution of the yeast was determined both by 

 radioactive measurements and by the usual chemical (colorimetric) 

 analysis. 



Yeast gro^vni 



Dry weight 

 of yeast 

 (mgm) 



Total P 

 found by 

 chemical 

 analysis 

 (mgm) 



Total P 



per mgm 



dry weight 



of yeast 



Mgm P taken up 



chem. 

 analysis 



radioactive 

 analysis 



Initial weight and P content of 

 yeast samples iised 



In labelled P with sugar at 25° 



In labelled P with sugar at 0° 



In labelled P without sugar at 20° 



1.966 

 1.987 

 2.095 



0.004 

 0.012 

 0.012 



0.044 

 0.054 



