PHOTOCHEMISTRY OF BACTERIOCHLOROPHYLL 



409 



In crude bacterial chromatophore suspensions a reversible bleaching 

 of a relatively large fraction of the 880 m^ band can be demonstrated 

 in some cases (Fig. 9), a small part of which is irreversible. In the 

 visible part of the spectrum, reversible cytochrome changes may ob- 

 scure changes due to reversibly bleached bacteriochlorophyll. Re- 



500 



Fig. 9. Difference spectra between illuminated and nonilluminated /?. rubmnt 

 chromatophores, measured with a standard Beckman recording spectrophoto- 

 meter. The spectra are disturbed due to the fact that the scanning time of the 

 machine is not short as compared to the spectral restoration times. In the 

 visible part of the spectrum a marked reversible cytochrome change is ob- 

 served, while the long wavelength part shows a reversible decrease at 880 myu, 



while a smaller increase around 860 m.^\s visible. before experiment, 



-..-..- after 5 minutes bleaching, after 20 minutes storage in the 



dark. 



versible bleaching at 880 m/i (phenomenon 1) here by far exceeds the 

 reversible shift (phenomenon 2) at 800 m/Y. It could be suggested that 

 we here have a reversible bleaching analogous to the one in Fig. 5, 

 time curves of spectral restoration being similar (Fig. 10), 



