432 HERRICK BALTSCHEFFSKY 



further to a compound X, which represents the site of action for HOQNO 

 [8] and antimycin A [9], and then to the photochemical oxidant. This is a 

 minimum scheme, based on our own results, and there probably exist 

 more electron carriers in the chain. For example, the participation of 

 cytochromes was indicated in earlier work by Smith and M. Baltscheffsky 

 [10]. In what may be called "the PMS-pathway " added PMS, serving as 

 a link between the flavoprotein and the oxidant, gives a new, "artificial" 



Light 



. ' 1 



reductant »- flavoprotein >- X >■ oxidant 



atebnn \ HOQNO 



antimycin A 



PMS 

 Fig. I. Electron transport in LIP chromatophores of R. riibrum. 



electron transport chain. When this pathway is used, the transport of 

 electrons from the reductant to the oxidant along "the physiological 

 pathway" can be ehminated by inhibition at X with HOQNO or 

 antimycin A [9, 11]. 



Light 



[ 



reductant 



1 



FMN, FAD 

 menadione 

 PMS, pyocyanine 



Fig. 2. Electron transport in LIP in spinach chloroplasts. 



In green plants, the ATP-formation which is linked to cyclic electron 

 transport is almost totally dependent upon the addition of an electron 

 carrier. Our tentative view about the electron transport in isolated spinach 

 chloroplasts is given in Fig. 2. A great similarity is seen between this 

 scheme and that proposed earlier by Jagendorf [12]. The main difference 

 is that flavoprotein has been included as an obligatory member in the 

 physiological electron transport chain. The experimental background for 

 this scheme has been presented earlier [5]. 



In recent experiments aiming at an estimation of the efficiency of light- 

 induced phosphorylation in vitro we have used three different approaches 



