43 



ously, it produced cataract and most people prefer being fat or 

 hungry to being blind. 



The mechanism of the action of dinitrophenol is the more 

 puzzling because it acts not only on oxidative phosphorylation, but 

 seems to act wherever energ}^ has to be transmitted and put to 

 action. It inhibits various processes involved in photosynthesis and 

 inhibits the "pumping activity" of cell membranes, in which os- 

 motic or electric work is done. These reactions are so different 

 that it was impossible to bring them to a common denominator 



OH 



N02 N02 



(a) (6) 



Fig. 7. a: 2,4-Dinitrophenol. b: 2,4-Dinitro-l-naphthoI. 



in terms of chemistry. The only point at which all these reactions 

 agree is that transmission of energy is involved, in one way or an- 

 other. This makes it seem likely that the dinitrophenol is not in- 

 volved in a definite chemical reaction, but acts rather through 

 some physical principle, as is the quenching of E*. It may be 

 interesting to note in this connection that both 2,4-dinitrophenol 

 and 2,4-dinitro-l-naphthol (Fig. 7b) have in the near infrared a 

 broad region of absorption. Dinitronaphthol is, essentially, dini- 

 trophenol with an extra antenna added to it. 



McLaughlin and the author measured the quenching of the 

 fluorescence of the aromatic hydrocarbon, chrysene, by a number 

 of aromatic nitro derivatives and found dinitrophenol active and 

 dinitronaphthol even more so. Unfortunately, their methods did 

 not allow them to distinguish between true quenching and the 

 simple competition for the light between quenching and quencher. 

 So Karreman and Steele repeated these measurements with more 

 adequate methods. Their results showed that both dinitrophenol 

 and dinitronaphthol are true quenchers. The quenching observed 



