491 



W. D. Bonner, jr. 



purified. The extraction and purification of cytochrome /, from parsley 

 leaves, was carried out according to Davenport and Hill (1952). 



The low temperature absolute absorption spectrum of partially purified 

 cytochrome /is shown in Fig. 12. With a sharp maximum at 552 m^ cyto- 

 chrome /can be easily distinguished, at —190°, from the other cytochrome 

 components that have been described here. No attempt has been made yet 



Z\0. D. = 0.02 

 i 



CYTOCHROME f 



I I I I I I I 

 520 550 



Fig. 12. The absolute absorption spectrum (at 

 cytochrome /preparation. 



190°C)ofa 



to investigate the absorption properties of the chloroplast b component, nor 

 of whole chloroplast suspensions. 



Roots 



Particulate preparations were obtained from roots with difficulty and in 

 small yields. Particulate preparations from barley roots showed maxima at 

 596, 558 and 551 m/n. The spectrum for a particulate preparation derived 

 from bean roots is shown in Fig. 13. It may be seen that reduction with 

 DPNH shows bands corresponding to cytochrome components (a + a^), 

 b and c ; after reduction with dithionite, a very large amount of dithionite- 

 reducible cytochrome appears. 



Cyanide Insensitive Respiration 



Only brief mention will be made here concerning cyanide-insensitive 

 respiration; for a detailed discussion see Bendall and Hill (1956), Chance 

 and Hackett (1959) and Bonner and Smith (1961). Those tissues which 

 exhibit, characteristically, cyanide-insensitive respiration have been examined 

 in detail for their cytochrome components. 'Mitochondrial fractions', 

 prepared from cyanide-insensitive tissues have been found to contain exactly 



