STUDIES OF THE CONSTITUTION AND PHOTOCHEMICAL ACTIVITY 

 OF AN ISOLATED CHLOROPHYLL COMPLEX 



M. B. Allen and J. C. Murchio 



This paper describes recent progress with investigations di- 

 rected toward the isolation and characterization of chlorophyll 

 complexes of living algal cells and study of the photochemical 

 activity of the isolated complexes. We have previously reported 

 (1,2) the isolation from Chlorella pyrenoidosa of a photochemi- 

 cally active chlorophyll complex with its red absorption maximum 

 at 672 m^ (P-672). This complex has a chlorophyll a/b ratio of 

 approximately 1, and also differs slightly from the bulk of the 

 chloroplast material in its carotenoids. On illumination it 

 forms a stable free radical that can be discharged by reaction 

 with natural or artificial electron acceptors. 



Under the best conditions so far achieved, the yield of P-672 

 is 1 to 1.5^ of the total chlorophyll of the cell. Success in 

 its preparation depends upon breaking the cells in the right 

 manner to separate this particular fragment from the chloroplast, 

 ajad upon centrifugation at the proper viscosity to effect its 

 sei)aration from other fragments. Even small variations in the 

 cell breaking processes of grinding and ultrasonic treatment re- 

 sult either in no yield or in the formation of a so far insepa- 

 rable mixture of products exhibiting a flat topped absorption 

 curve with maximum at 675 np. 



P-672 as obtained by previously described procedures was con- 

 taminated with a considerable amount of colorless material, some 

 of it particulate, including RNA. Treatment with ribonuclease 

 (RNAse), followed by washing, removed much of this material, as 

 evidenced both by microscopic observation and by a decrease in 

 absorbance in the 260-280 m^ region, with a concomitant increase 

 in ultraviolet absorption in the washings. Treatment with des- 

 oxyribonuclease had no effect. Incubation with papain resulted 

 in breakdown of the complex. 



Among the noteworthy properties of P-672 is a tendency to form 

 membranes whenever its concentration becomes great enough, be it 

 through centrifugation, freezing, or slow dehydration with silica 



486 



