BRITTON CHANCE 



by combining with b'\ since c'" can participate in oxidative 

 phosphorylation in the presence of antimycin-A (54). 



REVERSAL OF INHIBITION : 



LOCALIZATION OF SITES OF OXIDATIVE PHOSPHORYLATION 



The theorem above apphes conversely to the reversal of 

 inhibition, and this concept is particularly useful in analyzing 



T ^'0 



E 

 o 



c 



E t.05i 

 <u 



c 



c 

 Q 



DPNH 



f \ 



O 



a 

 O 



t.02 



t.oi- 



- 



-.01 



* ', 



V^' 



-^ 



320 



540 



580 



620 



360 410 450 



A{m>j) 



Fig. 4. The spectroscopic changes that occur in an aerobic mito- 

 chondrial suspension when added adenosinediphosphate is used up and 

 the respiration slackens owing to lack of phosphate acceptor (29). 



The mitochondria were initially carrying out oxidative phosphoryla- 

 tion (spectrum plotted as a horizontal base line), and as the added ADP is 

 exhausted the various absorption bands appear due to reduced cytochromes 

 b (564 m/Lt and 431 m;u), c (550 m/x and 420 m/x), and DPNH at 340 my.. The 

 absorption band of the oxidized form of flavoprotein which has an absorption 

 band at 465 my. disappears and leaves a trough at 465 m^u. The absorption 

 band of reduced cytochrome a disappears and leaves a trough at 605 my. 

 The changes at 445 m.y due to cytochrome m are too small to measure under 

 these conditions, but are readily recorded if a small azide concentration 

 ('^lOO /xM) is added (Expt. 359). 



the effect of ADP addition upon respiration and phosphorylation 

 in a "tightly coupled" mitochondrial preparation. In such a 

 case, electron transport through the system may be increased 



322 



