162 



R. P. Levine 



TPM photoreduction 



An investigation of TPN photoreduction showed that all of the mutant 

 strains possessed an active PPNR and pyridine nucleotide transhydrogenase' ^0^. 

 However, as shown in column five of Table I, chloroplast fragments from each 

 of the mutant strains were ineffective in the photoreduction of TPN in the 

 presence of an excess of purified PPNR when the source of electrons was 

 water(9' 10). On the other hand, all strains except ac- 208 were capable of TPN 

 photoreduction when the electron donor was a catalytic amount of DPIP in the 

 presence of a substrate concentration of ascorbate'*^' '^^K 



Photophosphorylation 



Recent investigations have revealed that wild type, ac- 115 , and ac- 141 

 are capable of carrying out cyclic photophosphorylation with PMS, or the 

 combination of vitamin K3 and FMN, as the added electron carriers whereas 

 ac-21 and ac-208 are not (22), Since ac-21 can photoreduce TPN from DPIP 

 and ascorbate, it was considered important to determine whether or not TPN 

 photoreduction could be accompanied by photophosphorylation in this strain. 

 The wild type strain can carry out non-cyclic photophosphorylation linked to 

 TPN reduction in this manner (Table 1). Numerous attempts with ac-21, how- 

 ever, have failed to give non-cyclic photophosphorylation, though in each 

 instance there was the expected rate of TPN reduction. 



Electron spin resonance 



Results of an investigation of electron spin resonance^ 1'*' have shown 

 that wild type, ac-21 and ac-208 have the two ESR signals (I, the fast, narrow 

 signal and II, the slow broad signal) that are characteristic of Chlorella, 

 Chlamydomonas, and Scenedesmus'23-25), However, signal II is missing in 

 ac-115 and ac-141. Signal I in C. reinhardi is light-dependent, and has an 

 action spectrum that resembles the absorption spectrum of chlorophyll a. 

 Signal II occurs in the absence of light, at least in cells that have been cultured 

 in the light^^). 



COMPONENTS OF THE 

 ELECTRON TRANSPORT SYSTEM OF PHOTOSYNTHESIS 



The inability of any one of the mutant strains to carry out normal photo- 

 synthesis might be accounted for on the basis of some change in either the 

 quantity or chemical nature of one of the possible components of the electron 

 transport system. We have analyzed, in part, the cytochrome b5, cytochrome f, 

 plastocyanin, plastoquinone, and carotenoid content of wild type, ac - 2 1 , ac- 1 15 , 

 and ac-14l(9' ^2, 13, 26), Since we are still engaged in these analyses, the data 

 presented here are incomplete. 



