95 



riboflavine (and, possibly, also suppressed oxidative phosphoryla- 

 tion) by stabilizing the triplet could be supported by the follow- 

 ing experiment: a riboflavine solution was frozen in the presence 

 of 0.1 M NaCl. Instead of the usual orange phosphorescence a 

 yellowish-white light emission was obtained. The white color in- 

 dicated the mixed nature of the emission, while its yellow tint 

 showed that fluorescence reappeared. That this actually was the 

 case could be shown by observing the frozen tube in the phos- 

 phoroscope which cuts out fluorescence. Here the system showed 

 a strong red phosphorescence, strong as compared to the tube with 

 no added NaQ. What the NaCl did was thus to render the system 

 unstable. The excited electrons of riboflavine could no longer go as 

 readily into the triplet as they did in pure ice, and if they did so 

 the triplet was rather unstable so that more electrons did emit their 

 energy in a radiative process and drop back to their ground level. 

 If KI is added in 10"^ M concentration in addition to the 0.1 AI 

 NaCl, the phosphorescent emission becomes weaker and the 

 fluorescence disappears. 



2,4-DINITROPHENOL 



The classic uncoupler is 2,4 dinitrophenol as shown in the 

 studies of Loomis and Lipmann. It does the uncoupling in low 

 concentration, at 10"* Af, and may do so without inhibiting oxida- 

 tion, which may even be increased. It is this action which made 

 nitrophenol into a reducing agent (used for reducing body 

 weight). Its medical dose is 100 mg, which means a random con- 

 centration of 10'^ Af in the body (60 kg body weight and 1.2 

 specific weight). But even smaller single doses, such as 25 mg, 

 can cause a rise of the basal metabolism by 30%, which would 

 mean a concentration in the body of 4 X ^^'^ ^- The molecule of 

 dinitrophenol is simple, has no characteristic solubilities, and so 

 we can suppose it to have no specific affinities to tissues or cell 

 constituents and to exert its pharmacological action at its random 

 concentration. So if we want to support the idea that dinitrophenol 



