448 



Norman I. Bishop and H. Gaffron 



contrary, but as expected from previous experiments, photoreduc- 

 tion showed no such stimulation and, at times, v;as even inhibited. 

 These data are summarized in Table Ml. 



TABLE Ml. COMPARISON OF THE EMERSON ENHANCEMENT EFFECT 

 IN PHOTOSYNTHESIS, PHOTOREDUCTI ON, AND PHOTOHYDROGEN 

 IN SCENEDESMUS D3. 



Wavelength of 

 Exci ting Li ght 



Photoreduction 

 (mm-^ gas 

 uptake/hr) 



Photosvnthesi s 

 (mm^ gas 

 uptake/hr) 



Photohydrogen 

 Production 

 ul H2/hr 



640 mu 

 705 tnu 

 705 mu + 640 mu 



54.6 

 46.8 

 80.6 



32 



8 



47 



26.6 



3.0 



38.0 



Ratio 



(640 + 705) 



(640) +(705) 



^=0.79 



40 



184= 1.28 

 29.6 



INFLUENCE OF UNCOUPLERS OF PHOSPHORYLATION 



In the original experiments of Gaffron and Rubin di ni trophenol 

 (DNP) was observed to exert a twofold effect on the hydrogen meta 

 holism of adapted cells: the dark formation of hydrogen was abol- 

 ished but photohydrogen formation was markedly stimulated. This 

 finding gave ample proof that two different systems were function- 

 ing in algal hydrogen metabolism. Because of the difficulty en- 

 countered with DNP in isolated chloroplast studies(15), m-chloro 

 carbonyl cyanide phenylhydrazone (CCCP) was employed to study the 

 role of phosphorylation in photohydrogen formation. Heytler re- 

 cently discovered that this compound and other derivatives are 

 potent uncouplers of phosphorylation reactions in general^ ' . 

 CCCP, like DNP, inhibits the dark formation of hydrogen and stim- 

 ulates the light induced hydrogen production. A typical experi- 

 ment demonstrating this is shown as part of Fig. 3. It is clear 



