HEMATIX COMPOUNDS IX PHOTOMETABOLISM 159 



teria in addition to the observations reported previously in this 

 s3^mposiiim. Lundegardh has claimed that, in Chlorella, illumination 

 causes an oxidation of cytochrome / and a barely detectable but 

 significant reduction of some h cytochrome (24). He has suggested a 

 scheme similar in many respects to that provided by Hill, in which 

 electron flow down the respiratory chain in the dark is reversed and 

 run backward through a "special cytochrome system in which cyto- 

 chrome / is one of the Hnks" (24). Recently, Hill has remarked (14) 

 that in leaves of certain "golden" varieties of plants a sharp band 

 corresponding to reduced cytochrome be, appears on illumination 

 in vivo, which can only be obtained from the chloroplasts isolated 

 from the same som-ces by treatment with hydrosulfite. There is also 

 an indication that, at the same time the h component is reduced, the 

 / component is oxidized. Here, as in the bacteria, no components other 

 than the hematin compounds in photosynthetic tissues show changes 

 in oxidation state of this magnitude upon illumination. It is evident 

 that this phase of research is in its infancy but Hke most infants it 

 can be regarded with optimism for the future. 



The acceptance of the notion that a back oxidation involving a 

 chain of hematin compounds occurs closely coupled with the photo- 

 chemical act would normally invite speculation about a subsequent 

 or concomitant phosphorylation. Such a phosphorylation would be 

 analogous to the coupling of phosphorylation and oxidation in nor- 

 mal respiration. However, no speculation is required, as experimental 

 data are at hand which appear to indicate that the photochemical act 

 can be coupled to phosphorylation under conditions where a normal 

 respiratory oxidation cannot occur (i.e., under strictly anaerobic 

 conditions). Frenkel (11), working with chromatophores from R. 

 ruhriim, has demonstrated that light under strictly anaerobic condi- 

 tions induces a disappearance of inorganic phosphate in the presence 

 of ADP which can be accounted for as newly formed ATP. 



In well-washed chromatophores this light-dependent phosphoryla- 

 tion is not accompanied by appreciable dark phosphorylation. It is 

 insensitive to the usual respiratory inhibitors and does not require 

 oxygen. In this respect, the light phosphorylation parallels the photo- 

 oxidation of cytochrome c by the same system (37). It is of interest 

 that 2,6-dichlorophenol-indophenol which can act as a substrate 

 in the photooxidation in air (37) suppresses the light anaerobic phos- 

 phorylation (11). Similar phenomena are noted in chloroplast sus- 



