INTRODUCTION 



Hegsted et al}'^ observed that chicks fed a purified diet containing 

 adequate pantothenic acid developed a dermatitis which was cured by 

 vitamin H. Biotin was also shown to be identical with coenzyme R/^' ^^ 

 a growth and respiratory factor essential for the nitrogen-fixing 

 Rhizohia present in the root-nodules of legumes. ^^ 



Actually the substance isolated by Kogl and Tonnis ' from egg- 

 yolk, though verj^ similar in chemical and biological properties to the 

 substance isolated by du Vigneaud and Gyorgy ^^ from liver, is prob- 

 ably not identical with it. F. Kogl and E. J. ten Ham ^^ found that 

 apparently significant differences existed between the melting points 

 and optical rotations of the two forms, and they designated the factor 

 from egg-yolk a-biotin and that from liver ^-biotin. The methyl 

 esters of the two substances also differed in melting point and optical 

 rotation, whilst a mixture of a- and j3-biotin methyl esters had a 

 melting point 20 to 30° lower than that of either of the pure esters. 

 The activity of j8-biotin in the yeast test was almost twice that of 

 a-biotin, although more recent tests against five different micro- 

 organisms suggests that a-biotin has 90 to 96 % of the activity of 

 ^-biotin.18 



References to Section i 



1. E. Wildiers, La Cellule, 1901, 18, 313. 



2. E. I. Fulmerand V. E. Nelson, Proc. Iowa Acad. Sci., 1922, 29, 371. 



3. W. Lash Miller, Science, 1924, 58, 197. 



4. E. V. Eastcott, /. Phys. Chem., 1928, 32, 1094. 



5. W. Lash Miller, Trans. Roy. Soc. Canada, III, 1936, 30, 99. 



6. C. Rainbow and L. R. Bishop, /. Inst. Brewing, 1939, 45, 593. 



7. F. Kogl and B. Tonnis, Z. physiol. Chem.-, 1936, 242, 43. 



8. W. Lash Miller, Trans. Roy. Soc, Canada, III, 1937, 31, 169. 



9. A. S. Schultz, L. Atkin and C. N. Frey, /. Amer. Chem. Soc, 1939, 



61, 1931- 



10. A. S. Schultz, L. Atkin and C. N. Frey, ibid., 1938, 60, 1514. 



11. M. A. Boas-Fixsen, Biochem. J., 1927, 21, 712. 



12. P. Gyorgy, Z. orztl. Fortbild., 1931, 28, 377, 417 ; /. Biol. Chem., 



1937. 119» xliii ; 1939, 131, 733. 



13. P. Gyorgy, D. B. Melville, D. Burk and V. du Vigneaud, Science, 



1940, 91, 243 ; V. du Vigneaud, D. B. Melville, P. Gyorgy and 

 C. S. Rose, ibid., 1940, 92, 62. 



14. D. M. Hegsted, J. J. Oleson, R. C. Mills, C. A. Elvehjem and E. B. 



Hart, /. Nutrition, 1940, 20, 599. 



15. R. Nilsson, G. Bjalfoe and D. Burstrom, Naturwiss., 1939, 27, 389 ; 



P. M. West and P. W. Wilson, Science, 1939, 89, 607, 



16. F. E. Allison, S. R. Hoover and D .Burk, ibid., 1933, 78, 217. 



17. F. Kogl and E. J. ten Ham, Naturwiss., 1943, 31, 208 ; Z. physiol. 



Chem., 1943, 279, 140. 



18. K. K. Krueger and W. H. Peterson, /. Biol. Chem., 1948, 173, 497. 



405 



