ROliERT HILL AND WALTER D. BONNER, JR. 425 



TABLE 1 

 Some Characteristics of Cytochromes / and h^ 



Cytochrome 



Absorption Maxima 



(25°C) 



Absorption Maxima 



(-190°C) 



(Volts) 



/ a-554.5, /3-524, 7-422 



bt a-563, /3-534, 7-429 



ai-552, /3,*-529, 7-420.8 +0.365 



a2-548, /32-524 



a-557, /3-530, 7-427 -0.030 



* 9 fl-bands can be observed at low temperature. 



sulfite reduction of ^shole chloroplasts. Since no absorption in the 

 region 550-560 m^ can be observed in the absence of hydrosulfite, 

 it may be concluded that in the light the readily discernible chloro- 

 plast cytochromes are oxidized. 



It has been shown by Hill and his associates (see Hill, 7) that the 

 two cytochrome components of chloroplasts are not denatured by 



552 



, 554.5 



400 



450 



500 



550 



600 



Fig. 1. Spectra of highly purified cytochrome /. Solid line, a low temperature 

 (_190°C) oxidized-rcduced difference spectrum. Dashed line, a room temperature 

 absolute spectrum. This latter spectrum was replotted from recent unpublished 

 data of H. E. Davenport. 



