452 BACTERIAL PHOTOSYNTHESIS 



not the chemistry of atomic nuclei. Atoms don't move, there is not 

 atomic chemistry, in the the sense of diffusion-limited processes. The 

 processes which precede the photochemistry involve only photon inter- 

 actions. All of this is over in ~10"9 seconds, and what the photochem- 

 ical apparatus has to be set up to do is to quickly grab the products 

 of a reaction which is over in 10-9 seconds, and which will dissipate 

 itself if nothing is done before the products back- react. So what we 

 have to find out is how this is arranged. 



So far we know what the primary electronic redistribution is. It 

 involves a movement of electrons from a region of low potential to a 

 region of high potential. The low potential is something near the oxygen 

 electrode; the high potential is something near the hydrogen electrode. 

 This isthesimpleprimary reaction, and this electron drift is stabilized 

 by the formation of products which live for as long at least as 10-3 

 seconds. They may live even longer, because we now seem to have, at 

 least in green plant photosynthesis, two processes which can be com- 

 bined over periods as long as 10 to 15 seconds, to give a high yield, 

 or to give an enhancement in yield. It is not clear to me that it is 

 necessary there be a two-quantum action for green plant photosynthe- 

 sis; nobody's shown us no photosynthesis for just one quantum at one 

 wavelength, but there is no question that there is an enhancement. Now 

 in bacterial photosynthesis, the pressing problem which has arisen, 

 and for which we are still awaiting the answer, is: Is there a two- 

 quantum or one-quantum process in bacterial photosynthesis? I've 

 heard opinions or sentiments expressed that there was a two-quantum 

 act in bacterial photosynthesis, and I've also heard other sentiments 

 expressed that there should be only a one-quantum act. Today, for 

 instance, we heard numerous examples of the camp which holds that 

 bacterial photosynthesis is merely green plant photosynthesis with the 

 one half knocked off. This remains to be established; it is certainly 

 simplest, however, to think of it that way. The data we have on 

 cytochrome-bacteriochlorophyll interactions was very well sum- 

 marized by Clayton, There is nothing from EPR work yet which helps 

 us in this respect, (See "Note added in proof," page 455,) 



As far as the photochemistry of bacteriochlorophyll is concerned, a 

 topic which was taken up by Goedheer, there is very interesting work 

 here, showing the necessity to reinvestigate the Krasnovsky reaction. 

 The data are in extreme confusion, Livingston has been looking into 

 this for the last two or three years and he is not certain just what the 

 phenomena are which are being seen. I won't go into some of the 

 strange spectra which show up in flash work, where you look at the 

 first steps of the reaction, but there is no question that in the reduction 

 of the dyes, especially in the reduction of chlorophyll in the Krasnovskj/ 

 reaction, there appear four or five transient intermediates which live 

 for very short periods of time before the final pink product shows up. 

 These can be shown to have very little to do with what is finally seen 



