APPLICATION OF PAPER CHROMATOGRAPHY 



1GG3 



confirmed, and their specific nature established. Seldom has the applica- 

 tion of a new method of analysis brought such sudden light into the dark- 

 ness and permitted the identification of so many compounds present in a 

 complex mixture only in microgram amounts. This work undoubtedly 

 constitutes one of the greatest successes so far of the isotopic tracer tech- 

 nique in chemical analysis ; but it could only be achieved by combination of 

 this method with chromatography, an analytical method which, although 

 almost fifty years old, has only recently been extended beyond its original 

 narrow field of application to organic pigments. 



The distribution of tracer carbon within the carbon chain of PGA, hex- 

 oses (cf. section 1), and of other early products also was reinvestigated. 

 Typical results of these "degradation experiments" are shown in table 

 36. V. It shows the initial preferential (or exclusive) labelling of the car- 

 boxyl group in PGA, malic acid and alanine, and gradual approach to 

 equidistribution, already noted before. This approach to isotopic equilib- 

 rium occurs in a closely parallel way in PGA, alanine and hexose. 



Table 36.V 



Distribution of Carbon 14 within the Carbon Chain in the Products of 

 Photosynthesis (10,000 f. c.) (after Calvin et al. 1950) 



Barley 



Position 



2 sec. 



15 sec. 



60 sec. 



Chlorella 

 5 sec. 



Phosphoglj^ceric acid 



COOH| 



CHOHJ 



I 

 CH.OH 



85 

 15 



56 

 21 

 23 



4-i 

 30 

 25 



95 

 3 

 2 



Alanine 



COOH 



CHNH, 



I 

 CHs 



67 

 30 

 30 



48 



44 



<5 



Sucrose 



C3,4 

 C2,5 

 Ci,6 



52 

 25 



24 



37 

 34 

 32 



Scenedesmus 

 30 sec. 



87 

 7 



6 



Malic acid 



COOH 



1 

 rest 



Scenedesmus 

 10 sec. 



93.5 

 6.5 



It will be noted that approximate equidistribution of C* in the sucrose 

 molecule is reached, according to table 36. V, already after 60 sec. exposure. 



