SPECTROSCOPIC PROPERTIES OF PURIFIED 



CYTOCHROMES OFPHOTOSYNTHETIC 



BACTERIA 1 



ROBERT G. BARTSCH 



Department of Chemistry, University of California, 

 San Diego, La Jolla, California 



The primary reason for studying pure cytochromes isolated from 

 photosynthetic bacteria is to correlate chemical and physical proper- 

 ties of an isolated cytochrome with the functional role of that cyto- 

 chrome in light-induced or dark electron transfer processes of the 

 cell. In addition, as emphasized by Kamen in this volume, p. 61, the 

 cytochromes that have been isolated from photosynthetic bacteria 

 possess distinctive properties which give them intrinsic interest as 

 heme proteins. Here is summarized the available information on 

 spectroscopic properties of various types of pure cytochromes isolated 

 from photosynthetic bacteria. 



METHODS 



When investigating absorption properties of the Soret band, cyto- 

 chrome concentration is chosen to give ferro-Soret bands of nearly 1 

 absorbancy. For the visible region 3-fold greater concentration is 

 used. The original Gary model- 14 spectrophotometer tracings are 

 reproduced to facilitate interpolation of wavelength or absorbancy 

 data and to preserve as faithfully as possible minor inflections in the 

 absorption curves which seem always to be obliterated in ink tracings 

 of the original spectra. 



Before dilution, cytochrome c samples are oxidized by adding ex- 

 cess ferricyanide to buffered stock solutions, after which the mixture 

 is passed through a G-25 Sephadex column to remove salts. Two suc- 

 cessive treatments with ferricyanide are necessary to completely 

 oxidize the cytochromes. The cytochromoid G (RHP)2 samples and 



1 The work reported here was performed in the laboratory of Professor M. D. 

 Kamen with support from the National Institutes of Health (Grant No.C-5992), 

 National Science Foundation (Grant No. G-19642), and the C. F. Kettering 

 Foundation. 



2 Cytochromoid C is the name suggested by the International Union of Biochem- 

 istry Commission on Enzymes (1) for the heme protein previously named RHP. 



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