13. On Oxidative Phosphorylation and 



Its Uncoupling 



One of the sites of most intense energy transmission in the cell 

 is the mitochondrion which oxidizes foodstuffs, transferring their 

 oxidative energy to ATP, stabilizing it in the form of ^P, and so 

 if £* is involved in biological energy transmissions then we can 

 expect it to have a hand in oxidative phosphorylation. We could 

 approach this problem from either of two directions. We could 

 ask whether substances known to uncouple oxidative phosphoryla- 

 tion have a special action on £* in concentrations in which they 

 uncouple, and we could ask whether substances known to act on 

 £* do uncouple oxidative phosphor)'lation.^ 



When attacking this problem we will have to go back for an 

 instant to the experiment with riboflavine, reproduced in Fig. 6. 

 In this experiment the vitamin was found to go on excitation 

 quantitatively into the triplet state and emit no light, as shown by 

 the middle tube in the figure. This absence of luminosit)' is in 

 agreement with rules of quantum mechanics which impose a strict 

 prohibition on the radiative transition from the triplet state into 

 the ground state. All the same, as witnessed by the next tube in 

 the same figure, in the presence of atmospheric oxygen, such a 

 transition does take place and the tube emits an orange phos- 

 phorescence with a wavelength of 570 m/x. This means that the O2 

 present altered transition probabilities, making transitions possible 

 which had practically no probability in its absence. If there is 

 oxidative phosphorylation there is also O2 and so we can expect 

 the vitamin to take part in this process in a perturbed state with 

 an altered reactivity. The O2 thus serves not only as a final elec- 



90 



