thi stability . of a auclein. For preparing nuclein from 

 yeasl cells, Felix Hoppe-Seylei I 1825 1895) described 

 the following details: Yeast is dispersed in watei to 

 extract soluble materials, like salts 01 sugars. Aftei .1 



few bonis, the insoluble material is separated, washed 

 once more with water, .uu\ then extracted with a ver) 

 dilute solution of sodium hydroxide. I he slightly 



alkaline solution, treed from insoluble residues, is 



slowly added to a weak hydrochloric aeid. A pre- 

 cipitate loi ins which is scpai.it ,-(l In lilt rat ion, washed 

 with dilute aeid. then with eold alcohol, and imalK ex- 

 tracted l>\ boiling alcohol ["he dried residue is the 

 nuclein li contains six percent phosphorus. A 



little more washing with water, a slightl) [1 1 



■ in with a< id oi alcohol gives produi ts oi lower 

 phosphorus content. Man) experimental variations 

 were necessar) to establish the procedure that leads 

 to purification without alteration of the natural 

 substance. 



1 Ins was also true for the methods oi chemical 

 degradation, carried out in order to find the com- 

 ponents ol nueleins in their highest State ol natural 

 Complexity. It was learned lor example, that the 



special kind of carbohydrate present in nueleins was 

 \er\ susceptible to change under the conditions ol' 

 hydrolysis b) acids. Phoebus Aaron Theodoi Levine 

 1 1869 1940), therefore, used the digestion l>\ a 

 living organism. With I'.. S. London, he introduced 

 a solution of nucleic acid into, e.g., the gastrointestinal 

 segment ol a dog through a gastric fistula and with- 

 drew the product of digestion through an intestinal 

 fistula. Fortunately, the products obtained in such 

 degradations were not new- in themselves. The 

 carbohydrate in this nucleic acid proved to he 

 identical with D-ribose, which Emil Fischei had 

 artificially made from arabinose and named ribose 

 to indicate this relationship (1891). The nitrogenous 

 products ol the degradation were identical with 

 Substances previously prepared in the long study of 

 inn acid. In the course of this study, Emil Fischer 

 established uric acid and a number of its derivatives 

 as having the elementar\ skeleton of what he called 

 "pure uric acid." abbreviated to purine. Out of 

 Adolf Baeyer's work on barbituric acid came the 

 knowledge ol pyrimidine and its derivatives. 



From these findings, together with what Oswald 

 Schmiedeberg (l!!:5r> 1921) had established conccrn- 



M A. WuRT, Dictionnairi deChimie, supp. part 2, [n.d.| p. 1087; 

 A ECOSSBL, £filschrijt fur pkysinlogische Chi erii I i 1 H7 l »), 



p. 284. 



PAPER 40: HISTORY OF PHOSPHORUS 

 224 527 67 r 



Figun i i ii i k' -I i 



/ed the Ni 'l"-l Prize in 

 Medic ine ami I'ln siolog) in ig 

 his work on inn leic substances, which 



i .mi a high |iiiipiii don ol |'I 



phorus. I In- i hemii al b mds ol this 

 phosphorus in tin- moleculi 

 nucleii substances were determined 

 in later work. [Photo mutt, »i National 

 Library of Medicine, Washington, P < 



ing the presence of four phosphate groups in the 

 molecule (1899), Robert Fculuen i 1 .'•!.". 1 l'Oa) con- 

 structed the following scheme of a nucleic acid. 

 Feulgen's formula of 1918 is: 



Phosphoric acid Carbohydrate Guanine 

 Phosphoric acid Carbohydrate -Cytosine 

 Phosphoric acid — Carbohydrate Thymine 

 Phosphoric acid — Carbohydrate Adenine 

 Of the four basic components on the right, tin mini- 

 occurs in the nucleidic acid from the thymus gland. 

 Yeasl contains uracil instead. The difference be- 

 tween tins,- two basis is one methyl group: thymine 

 is a 5-methyluracil. In all of these basic substances, 



Ml 

 / 

 / 

 the structure of urea C=0 is involved, and they 



XH, 

 form pairs of oxidized and reduced st 



193 



