436 HERRICK BALTSCHEFFSKY 



TABLE II 



Quantum Requirement for LIP in Chromatophores of R. rubrum 



The wavelength of the light was 862 m/<.. In experiments I and II sand had 

 been used for the grinding, in experiment III alumina had been used. The values 

 were obtained from the initial slopes of the curves for esterification of orthophos- 

 phate versus light-intensity. 



[3], except that the intact cells were disrupted by grinding with sand instead 

 of alumina. The method was developed last year in this laboratory [16]. 

 Pre-ageing the chromatophores at 55-57° influenced light-induced 

 phosphorylation as is shown in Fig. 5. It is the third type of experiment 

 suggesting that phosphorylation may occur at two sites in "the physio- 

 logical pathway" for the electron transport and at only one site in "the 

 PMS-pathway ". As is evident from the figure, pre-ageing decreases the 

 phosphorylation much more in the "physiological" system than in the 



PMS+ HOQNO 



No additions 



Pre-aging (min) 



Fig. 5. LIP in R. rubrum after pre-ageing. The experiment was performed 

 immediately after the pre-ageing, which was made at 55-57 • 



system where PMS and HOQNO have been added. Thus the phos- 

 phorylation at the single site of ATP-formation in "the PMS-pathway" 

 appears to be more stable than that at the valinomycin-sensitive site which 

 according to our hypothesis exists in "the physiological pathway" 



