spectroscopy of Flash-Illuminated Ghloroplasts* 



J. L. ROSENBERG, S. TAIvASHIMA, and RUFUS LUMRY, Departments 

 of Chemistry of the University of Pittsburgh and the University of Minnesota 



The existence of an excited meta stable electronic state of chloro- 

 phyll has been postulated for some time as a crucial intermediate in 

 chlorophyll photosensitized reactions (3). Porter and co-workers have 

 recently shown that many organic substances can be converted with 

 high yield to their metastable states when excited with the intense 

 light of a flash. Direct proof of the existence of such a state can be 

 obtained by a rapid recording of the absorption spectrum immediately 

 after the flash (6). Livingston (5) and Linschitz (4), using these 

 methods, succeeded in measuring the absorption spectrum of the 

 lowest metastable state of chlorophyll dissolved in oxygen-free organic 

 soh^ents. In this paper we are reporting results of our attempts to 

 observe the same phenomenon in flash-illuminated chloroplasts. 



The flash and spectrographic equipment were those of Livingston.! 

 In each experiment two flashes of light were used, separated in time 

 by about 30 to 40 microseconds. The first was the photolytic flash, 

 about 10 to 20 microseconds half-life, which concentrated light from 

 a 50-joule gas discharge upon the sample. The second was a spectro- 

 scopic flash, which sent a collimated beam through the sample and 

 then into the spectrograph. The entire absorption spectrum from 440 

 to 680 m^t was recorded instantaneously on a spectrographic plate. 

 Scattering of some of the photolytic light by the sample into the spec- 

 trograph was restricted to the long-wa\'elength region by the use of a 

 red cellophane filter around the sample tube. The filter reduced the 

 amount of energy available at the sample, but the red light trans- 

 mitted was intense enough to convert into its metastable state over 

 70% of the chlorophyll in a benzene solution which Avas used as a con- 

 trol. 



* These studies were aided by contract between the Office of Naval Research, 

 Department of the Navy, and the University of Minne.sota, NR 120-300. 



t We are ind(4)te(l to ])i-. Livingston for pcrniission to use these facilities. We 

 also wish to acknowledge the geneious a.ssistance of Dr. David Tanner, who 

 patiently instructed us in the operation of the eciuipment. 



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