11. CIliailSTKY 



101 



l)i('s.sui(' coiilniiis an amount of w alcr cori-cspondiiig rou^hlx' I o a diliydi'alo. 

 Samples dried at 14.') in jiioh xaciium lose this water of crysttdli/ation and 

 become hygroscopic. 



Pterovljj;lutamic acid has a characteristic ultraviolet absorption spectrum 

 (Waller d alP) which is markedly influenced by pli (Fig. 3). Tn O.l N 

 sodium hydroxide it exhibits maxima at 'ioG, 282, and 305 m/x with K\^m. 

 \alues of 585, 570, and 20G. The peaks at 256 and 365 m/x are due to the 

 pteridine ])ortion of the molecule: the peak at 282 is due to the p-amino- 

 benzoic acid moietv. The "lutamic acid exerts very little effect on the ultra- 



800 



600 



400 



200 



220 



260 



380 



420 



300 340 



X, m/i 

 Fig. 3. Ultraviolet absorj)tion spectra: (1) synthetic PGA in 0.1 N sodium li_v- 

 droxide: (2) synthetic PG.\ in 0.1 A' hydrochloric acid; (3) natural liver PGA in 0.1 

 xV sodium hydro.\ide: (4) natural liver PG.\ in 0.1 A" hydrochloric acid; (5) pteroic 

 acid in 0.1 A' sodium hydroxide. Courtesy ./. Am. Chein. Soc. (Waller ct al. ''■'). 



violet absolution spectrum. The absorption spectrum of pteroic acid (Fig. 

 3) is slightly different from that of PGA. However, addition of more than 

 one glutamic acid does not change the position of the absorption peaks, and 

 the extinction coefficients of PGA conjugates are in inverse proportion to 

 their molecular weights. 



1. Hydrogen.vtiox 



Pteroylglutamic acid and related pterins are readily hydrogenated and 

 can be reoxidized by atmospheric oxygen. O'Dell ct al.-^ found that i)teroyl- 



-■ C. W. Waller, li. L. llutc iiiuKs, J. II. Mowat, E. L. R. Stokstad, J. II. Hoothe, 

 R. B. Angier, J. 8emb, Y. .SubbaRow, D. B. Cosulich, M. J. Fahrenbach. M. E. 

 Hultquist, E. Kuh, E. H. Xorthey, D. R. Seeder, .1. P. Sickels, and J. M. Smith, 

 Jr., J. Am. Chem. Soc. 70, 19 (1948). 



