THE NATURAL STATE OF PROTOCHLOllOPHYLL 



405 



Through our work ou protochlorophyll, it has become evident 

 that an approach to this aim may be at hand. It has been possible 

 to remove the protochlorophyll holochrome from the leaf and trans- 

 form it by illumination to the chlorophyll holochrome. Thus the in- 

 tact natural pigment has been separated from its biological environ- 

 ment in a physiologically active state. If this unit can be isolated and 

 purified while still retaining its physiological activity, it should be 

 feasible to estabUsh its chemical structure. Fortunately, the test for 

 physiological activity is simple: the protochlorophyll holochrome is 



600 



700 800 



WAVELENGTH 



900 



Fig. 1. The transformation of protochlorophyll holochrome to chlorophyll-a 

 holochrome in a glycerine extract of etiolated bean leaves. 



transformed by light to the chlorophyll holochrome and the con- 

 version estimated by spectrophotometric analysis. 



Only a beginning has been made in this project, but the initial re- 

 sults are promising. The purpose of this paper is to describe briefly 

 what has been accomplished in regard to the isolation of the holo- 

 chrome and to report some of the observations made on the nature of 

 the holochromes. 



In our early experiments (3) we obtained extracts of the proto- 

 chlorophyll holochrome in glycerine. The dark-grown leaves or cotyle- 

 dons were ground for 10 or 15 minutes in a mortar with from 3 to 4 

 times their weight of undiluted glycerine. The extract w^as squeezed 

 through a fine-woven cloth and centrifuged for 10 to 15 minutes at 

 10,000 X g. All these operations were carried out in a dark coldroom 



