192 



RADIATION HIOLOGY 



Karrer et al., 1936) and may then be restored by reduction. The dis- 

 appearance and reappearance of this band in the spectra of coenzymes I 

 and II (Fig. 5-25) (Euler et al., 1936; Warburg et al., 1935; Horecker and 

 Kornberg, 1948) have been made the basis of elegant studies of the 

 respiratory and fermentative enzymes by Warburg (1949). 



Pyridoxine in neutral solution has absorption bands with maxima at 

 330 m/i (e = 5500) and 255 m/x (e = 2800). In alkaline solution these 



CH2OH 

 I 



HOHpC — nS— OH 



15 



10 



N 



-CH, 



6 r 



4 - 



2 - 



400 



360 320 



WAVE LENGTH, 



280 



240 



Fig. 5-25. Absorption spectra of re- 

 duced and oxidized cozymase. I, 

 reduced cozymase; II, oxidized co- 

 zymase. (Euler et al., 1936; repro- 

 duced from Hoppe-Seyler's Zeitschrift 

 fur physiologische Chemie.) 



300 340 370 



WAVE LENGTH, mu 



Fig. 5-26. Influence of pH on the absorption 

 spectrum of pyridoxine (vitamin Be). I, pH 

 2; II, pH 4; III, pH 5; IV, pH 7. {From W. R. 

 Erode, 1946, The Absorption Spectra of Vita- 

 mins, Hormones, and Enzymes. In, Advances 

 in Enzymolocjy, Vol. IV, F. F. Nord and C. H. 

 Werkman, ed., copyright, 1944, by Interscience 

 Publishers, Inc., New York.) 



maxima are displaced toward shorter wave lengths, but in acid solution 

 l)oth maxima disappear and are replaced by a new peak at 292 mp, 

 (e = ()()00) (Fig. 5-26) (Morton, 1942; Brode, 1946; Stiller el al., 1939). 



Vitamin B12 has two strong ultraviolet absorption bands with maxima 

 at 2780 A (E^Z = 115) and 3610 A iE\2, = 204) in addition to the 

 weaker band in the visible spectrum at 5500 A (fi'lJ,^ = 63) (Brink et al., 

 1949). Vitamins B12,. and B121, have similar spectra (Kaczka et al., 1949; 

 Brockman et al., 1950). 



Ascorbic acid in neutral solution has a strong absorption band 

 (e = 9300) at 265 n\p, which shifts to 245 m/i in acid (Morton, 1942). 



