The Fast Light Reaction of Extracts and of 

 Inhibited Cell Suspensions 



BRITTON CHANCE, MARGARETA BAT.TSCHEFFSKY, and LUCILE 

 SMITH, Johnson Fotwdationfor Medical Physics, University of Pennsylvania, 



Philadelphia , Pennsylvan ia 



As indicated in the preceding paper, the hemoprotein absorption 

 bands, that disappear upon infrared illumination of anaerobic whole- 

 cell suspensions of R. ruhrum, do so in a two-step reaction that in- 

 volves different members in the sequence of electron transfer reac- 

 tions. It was also found that an effect of the opposite sign is recorded 

 when the cells are treated with phenyl mercuric acetate. In this case a 

 strong absorption band in the region of 430 m/x appears when the 

 aerobic suspension is illuminated and this was then interpreted as a 

 photoreduction of hemoprotein (1). On the other hand, Duysens, who 

 has found that aerobic cells treated for some time with distilled 

 water give spectroscopic responses to infrared illumination similar to 

 those caused by phenyl mercuric acetate, proposes that the absorp- 

 tion band that appears upon infrared illumination is caused by an 

 oxidation product of bacteriochlorophyll instead of by a reduced 

 hemoprotein (2). 



Extracts of R. rubrum prepared according to Frenkel (3) also show 

 spectroscopic effects upon illumination, which resemble those observed 

 in whole cells treated with phenyl mercuric acetate. 



This paper compares the various conditions that lead to the 

 appearance of an absorption band in the region of 430 m/x upon infra- 

 red illumination and includes some discussion on the nature of the 

 compound observed. 



METHOD 



The double-beam spectrophotometer used in the studies of the 

 whole-cell suspensions was employed (1). The cross-illumination sys- 

 tem used two Wratten 88A filters and a gray filter of density 1 to 5 

 depending upon the infrared illumination needed to give maximal 

 spectroscopic effect. The monochromatic light intensity was main- 

 tained as low as practicable. 



192 



