86 



LIGHT AND LIFE 



QUENCHING OF FLUORESCENCE 

 BY HYDROXYLAMINE 



4.0 



3.0 



Fo-' 



2.0 



1.0 



PHENOL SERIES INDOLE SERIES 



X 



TRYPTOPHAN 



TYR Me ESTER 

 PHENOL 



G LY C Y L 

 TRYPTOPHAN 

 X 



TRYPTOPHAN 

 MP ESTER 



0.5 



1.0 



CONC. OF HYDROXYLAMINE 



Fig. 3. Quenching of the Huorescencc of plicnol and indole derivatives by hy- 

 droxylamine. Abscissa, molarity of hydroxy laniine. Ordinate: f„, original fluores- 

 cence efficiency; F, fluorescence efficiency upon addition of hydroxylamine. 



RKH* + OH 

 RN* -^ RN- 

 RN~ + OHo 



RNH* 



-^ RN*- + OH. 

 (radiatioiiless transition) 

 . 7^NH + OH- 



where RNH stands tor the indole nucleus. The requirement of a 

 mobile hydrogen lor the reaction is demonstrated by the fact that 

 N-methyl indole is not cjiienchcd in alkaline solution. It may be 

 pointed out that similar reactions with the hydroxyl ion have been 

 postulated by Rollclson and by Forster lor the naphthylainines, and 



