182 



MACROMOLECULAR COMPLEXES 



The systematic study has progressively elevated the status of the 

 chromatophore from that of a submicroscopic, pigmented particle 

 which appears when the cells are broken, to the status of a photo- 

 chemical organelle with a well-defined structure and a specific func- 

 tion. Using this point of view we shall consider the chromatophore 

 at three conceptual levels: (1) as a pigmented particle, (2) as the 

 structural and functional unit of photophosphorylation, and (3) as 

 the photochemical organelle. Then we will present our interpreta- 

 tion of the electron-optical image of the chromatophore and a hy- 

 pothesis of the molecular architecture. 



The Chromatophore as a Submicroscopic 

 Pigmented Particle 



Isolation. The structures which we identify (Bergeron et al., 

 1957) as the chromatophores of Chromatiiim can be obtained in 

 quantity by the procedure which is outlined in Fig. 2. The buffered 

 0.5M sucrose medium is a recent refinement which was designed to 

 maintain the physiological relationship between the carotenoid pig- 

 ments and the bacteriochlorophyll (Bergeron, 1958; Bergeron and 

 Fuller, 1959; Anderson et al, 1958). After the chromatophores have 

 sedimented, the preparation is washed by resuspension and recen- 



Fig. 2. The procedure used for isolating the Chromatium chromatophores. 

 The final preparation is washed two or three times by recentrifugation in the 

 buffered medium. 



