324 CONTROL OF REPRODUCTION 



RESULTS AND DISCUSSION 



The fluorescence spectrum of component 1 in O.IA^ HCl showed a 

 maximum at 505 m/x. The fluorescence spectrum of component 2 in 

 methanol has a maximum at 473 ni/^. 



Absorption spectra of the two substances were taken in both the 

 ultraviolet and visible regions with a model DU Beckman spectro- 

 photometer. Previous spectral studies by Gray (1953) and Allman 

 (1955) had been restricted to the visible. It was the ultraviolet spectra 

 which first provided us with a clue as to the chemical nature of the two 

 pigments. Component 1 in acid solution has a very prominent peak in 

 the visible at 420 ni/x, and a smaller inconspicuous maximum in the 

 region of 260-280 m/^. In neutral solution, the position of these peaks 

 is changed to 380 ni/x and 245 m/x. In alkaline solution, the 380-m/A 

 peak is unchanged, but the other peak shifts to 265 mfi. 



Component 2 in acid solution Hkewise has a spectrum with two 

 maxima, located at 330-340 m/x and at 260 ni/x. In neutral solution, 

 the 260-m;u peak is unchanged, but the longer wavelength maximum is 

 shifted slightly to 340-345 mix. In alkaline solution, the short-wave- 

 length peak is shifted to 265 m/x, and the long-wavelength maximum 

 is broadened in the region of 330-350 m/x. 



The possession of two absorption maxima in the ultraviolet or near 

 ultraviolet, the shifts in position of maxima with change in pH, and 

 the fluorescence of the compounds in question indicate that compo- 

 nent 1 and component 2 are pteridines (Gates, 1947; Wolstenholme 

 and Cameron, 1954; Albert, 1954). It has not been possible to 

 identify either component 1 or component 2 with any known com- 

 pound of this group, ^ 



Through the kindness of Dr. Ernest A. Jones, the two pigments 



1 Biological verification of the identity of component 1 as a pteridine was 

 obtained by microbiological assay with the flagellate Crithidia fasciculata, 

 which requires for growth both a conjugated and an unconjugated pteridine 

 (Nathan et ah, 1956). The growth factor activity of component 1 in the 

 presence of low levels of folic acid, but not in the presence of Crithidia factor, 

 indicates that component 1 is an unconjugated trisubstituted pteridine. The 

 author gratefully acknowledges the kindness of Miss Helene A. Nathan, Haskins 

 Laboratories, New York 17, N. Y., in performing this bioassay. 



