48 



Bessel Kok 



removes practically all chlorophyll and P700 and the extracted 

 material shows an emission spectrum identical to that of a 

 dilute chlorophyll solution. Treatment with 65-70% acetone, 

 which barely yields a loss of P700, results in material which 

 shows relatively less fluorescence at 730 mu and relatively 

 more at 685 and 698 mu. As was to be expected, the emission 

 of such preparations is not affected by the redox state of P700. 

 The data of Fig, 2 indicate a closer correlation of P700 with 

 the two short wave bands than with the long wave emissionCs). 



600 550 700 



WAVELENGTH mp. 



700 750 



WAVELENGTH m^ 



Figure 3 Figure h 



Figures 3 and k show data obtained with normal Scenedesmus 

 cells and mutant #8 of Dr. N. Bishop. This mutant is capable 

 of performing the quinone Hill reaction but not photosynthe- 

 sis and photoreduction. Vi/eaver and Bishop (8) noticed that 

 it lacked the light induced fast EPR signal, according to 

 Beinert, et al., (9) due to the oxidized form of P700. lie 

 indeed, did not find a light induced turnover of P700 in this 

 mutant or extracts prepared from it. The difference between 

 the two absorption spectra in Fig. 3 shows a distinct band at 

 700 mu amounting to ^10% of the absorbance at 678 mu. This 

 confirms Butler's (k) and Brown and French's (lO) earlier ob- 

 servations of long wave absorption bands. One is tempted to 

 identify "C7OO" with the small amount (-5%) of long wave 

 "oriented" chlorophyll which will be discussed in this sym- 

 posium by Dr. R. Olson (cf. also 11). The high concentration 

 of C7OO and its failure to undergo reversible photobleaching, 

 argue against its identity with photocatalyst P700. On the 

 other hand, the ability of the mutant to evolve oxygen |be it 

 at lower than normal rate (8)] despite the virtual absence of 

 C7OO suggests that both pigments are part of photosystem I. 



