326 



JAMES H. C. SMITH 



possible situations. One is that on any individual holochrome particle no 

 fixed ratio of yellow pigments to protochlorophyll exists. This means, 

 therefore, that the holochrome cannot be a definite compound. The other 

 situation is that lack in uniformity of composition results from con- 

 tamination of the protochlorophyll holochrome by carotenoid holochromes. 

 If this is true, the carotenoid and protochlorophyll holochromes must have 

 very similar sedimentation and precipitation properties. 



400 



500 



450 

 Wavelength (m/i) 



Fig. I. Absorption spectra of carotenoid fractions from protochlorophyll 

 holochrome isolated by chromatography on columns of powdered cellulose. 



The carotenoids were extracted from the pigment-protein complex, 

 named protochlorophyll holochrome, with 8o",, acetone. They were then 

 transferred to petroleum ether and chromatographed on powdered 

 cellulose. The chromatograms were developed by various mixtures of 

 acetone in petroleum ether. 



Positive identification of the individual carotenoids has not been made, 

 but from the shapes of the absorption curves, the positions of the maxima, 

 and certain colour reactions the pigments have been tentatively identified 

 as lutein epoxide ester (curve i), lutein (curve 2), isolutein (curve 3), and 

 violaxanthin h (curve 4). These assignments dilTer from those given the 

 carotenoids from etiolated bean leaves {Phaseolus vulgaris) by Goodwin 

 and Phagpolngarm [4] who have identified the following: /3-carotene, 

 10-8% of the carotenoid pigments present, lutein, 38 •4",,, neoxanthin, 

 50-7%, and a trace of an unknown yellow pigment. At present it is im- 

 possible to evaluate the cause of the discrepancies. 



The function of the carotenoids in the holochrome is still unknown. 

 Previously, it was intimated that these pigments played an obscure role in 



