CORRELATION BETl'.rEEN ABSORPTION CHAl^IGES AND ELECTRON TRANSPORT IN 



PHOTOSYNTHESIS 



B. Rumberg, P. Schmidt-Mende , J. Weikard and H.T. Witt 



With the method of sensitive flash photometry we separated 

 and analyzed as yet 7 different types of absorption changes. By 

 this method it was possible to derive a rather detailed reaction 

 scheme on the electron transport system in photosynthesis (1). 

 In the following we will discuss some more details which support 

 the probability of this scheme. 



I. PHOTOOXIDATION OF CHLOROPHYLL - a ^- 



Under "normal" conditions (eJiiting photosynthesis with red 

 light between 65o - 7oo rau) mixed absorption changes can be ob- 

 served between ^oo - 800 mu in chloroplasts and chlorella (s. 

 fig.1 top) (this difference spectrum does not include the ab- 

 sorption changes with life times .^ I0 ^ sec). 



The changes at 7o3 mu were discovered by Kok (2). The com- 

 pound causing these changes he called P 7oo. He reported also 

 changes at ^5o mu in inactivated aceton-extracted chloroplasts 

 (3) and suggested that both changes may be caused by a chloro- 

 phyll-a. But according to our measurements (1) there exist at 

 least 5 different types of absorption changes around 45o mu 

 caused by different compounds. Therefore, it is not established 

 that P 700 is a chlorophyll-a. We tried therefore to separate 

 out of the overall difference spectrum in photoactive prepara- 

 tions the spectrum which belongs to P 7oo only. 



1 . Separation of the difference spectrum of chlorophyll-a -j- 

 in 3 way s 



a) Aged chloroplasts . Aged chloroplasts (spinach) reactivated 

 by addition of reduced PIVIS (ascorbic acid in excess) show a 

 simplified difference spectrum (4) very similar to that shown 

 in fig.1, bottom. 



b) Plastoquinone extracted chloroplasts . Plastoquinone ex- 

 tracted chloroplasts (by petroleum ether) show a simplified 

 spectrum (s. fig.1, bottom), which is very similar to that men- 

 tioned under a) . 



c) Addition of CMU to chloroplasts . CMU-poisoned chlorella 

 or chloroplasts show a difference spectrum which is similar 

 with that of a) and b). 



d) Trapping at -1^o°C . The difference spectrum of trapped 

 products (i) at -150^^0 of fresh chloroplasts is shown in the 



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