VISCOSITY AND REACTION RATES IN BACTERIA 359 



that physical- chemical studies of the reaction mechanisms in the 

 chromatophore and, in fact, in the whole bacterial cell, might lead to 

 a "preview" of what the electron micrographs may eventually reveal, 

 we have most recently studied the effects of viscosity upon the kinetics 

 of electron transport in Rhodospirillum riibnim and Chromatium, and 

 have compared these results with those observed in the oxygen- linked 

 systems, 



EFFECT OF VISCOSITY UPON REACTION VELOCITIES IN 

 ELECTRON TRANSPORT SYSTEMS 



Effect of viscosity upon the cytochrome chain. 



As a model for studies in photosynthetic systems, we have tested 

 the effects of glycerol upon reaction rates in the cytochrome chain of 

 intact cells and nonphosphorylating particles derived therefrom 

 (Table 1), The data show almost complete inhibition of ethanol oxida- 



TABLE 1. 



Inhibition Of Electron Transfer By Glycerol 

 (Expt.942-E)(26*') 



tion in a suspension of baker's yeast treated with 40 per cent glycerol. 

 No specific site of inhibition could be detected as the glycerol concen- 

 tration increased; in spite of the presence of glycerol and a large de- 

 crease of electron flow, the steady states of reduction of the carriers 

 were remarkably constant, indicating that the effects of glycerol were 

 not centered at a particular site but were distributed over a number 

 of interaction sites in the chain. Nevertheless, it was considered 

 important to repeat this result with a cell-free, nonphosphorylating 

 system, and the data show very high inhibition in the oxidation of 

 DPNH or succinate (11), Similar results have been observed when the 

 electron transport system is suspended in deuterium oxide, and a 

 similar interpretation has been proposed (12). It appears that glycerol 

 and D2O reach the phase in which the carriers interact, presumably 

 in a water phase. From these results it appears that electron trans- 

 port between hematins is due totheir vibration and rotation about their 



