LIGHT-INDUCED PHOSPHORYLATION 



439 



which gives an appreciable degree of stimulation only in pre-aged prepara- 

 tions [6]. However, also with PMS, in preparations with activities of about 

 600 /xmoles of orthophosphate esteriiied per hour per mg. chlorophyll, or 



chlorophyll 

 (reduced) 



DPNH 

 Succinate 



cylochrofne c, 

 (oxidized) 



Qscorbate 



' Fig. 7. 



higher, the degree of stimulation has been relatively low, as low as 50% 

 or less. The two agents must stimulate phosphate esterification bv bridging 

 different parts of the electron transport chain, as antimycin A exerts a 



TABLE IV 



Menadione and PMS as Electron Carriers in LIP in 

 Chromatophores of R. rubrum 



The experimental details were as described in ref. [3]. The final concentrations 

 of the various agents were, where added: 3'3 x lo"^* m ATP, 10"^^ M menadione, 

 and 3 3 X io~* M PMS. The time for the experiment was 20 min. in the absence 

 and 6 min. in the presence of PMS. 



* In experiment II the chromatophores had been partly destroyed by heating 

 10 min. in a water-bath of 55-57 immediately before the actual experiment. 



Strong inhibition only on the stimulation due to addition of menadione. 

 This is seen especially clearly in the experiment with the pre-aged sample. 

 A comparison between the values obtained with the fresh and the pre-aged 

 material further show^s that the stability of the three systems increases in 

 the order: system with no added electron carrier, system with added 

 menadione, and system with added PMS. This sequence has been shown 



