186 MACROMOLECULAR COMPLEXES 



It should be noted that the carotenoids occur as a variable mix- 

 ture of several types, particularly lycopene, spirilloxanthin, and ly- 

 coxanthin ( Goodwin and Land, 1956 ) . It is also possible to interfere 

 with carotenoid synthesis by treatment with diphenylamine (Good- 

 win and Osman, 1954) and obtain chromatophores which appear to 

 totally lack the colored carotenoids (Anderson and Fuller, 1958; 

 Bergeron and Fuller, 1959); however, poorly colored precursors 

 appear to be present instead (reviewed by Stanier, 1958). Since the 

 carotenoid :bacteriochlorophyll ratio observed above agrees with 

 the ratio reported by Newton and Newton (1957), and with the 

 maximum value observed by Stanier ( 1958 ) in Rhodopseudomonas 

 spheroides, it seems safe to assume that these chromatophores also 

 contained about the maximum amount of colored carotenoids. 



The status of polysaccharide as a "fixed" component is debatable. 

 Newton and Newton ( 1957 ) describe polysaccharide in their "small 

 particle" fraction ( 100,000 g, 90 min ) . Their data show that in 

 passing from the "chromatophore fraction" ( 25,000 g, 60 min ) to the 

 "small particle," the phospholipid and chlorophyll content double on 

 a protein basis while the polysaccharide content decreases by a fac- 

 tor of three and one-half. These authors suggested that the chroma- 

 tophore consists of pigmented macromolecules in a carbohydrate 

 envelope. Newton (1958) has elaborated this point of view on the 

 basis of the immunochemical properties of intact cells and pigmented 

 fractions. 



Our data, particularly the electron microscope observations on 

 thin sections ( see below ) , indicate that the chromatophore ( 144,000 

 g, 90 min ) is in the "small particle" fraction of Newton ( 100,000 g, 

 60 min ) . Irregular cell fragments are common in the 25,000 g frac- 

 tion, which was identified with the chromatophore by Newton. 

 For this reason, we interpret the data on carbohydrate release as 

 evidence that it is a contaminant and not an integral part of the 

 chromatophore. 



The relation to the chromatophores of several biologicaljv im- 

 portant compounds, i.e., pyridine nucleotides, cvtochrome, co- 

 enzyme Q-, and vitamin K, is of special interest but remains obscure. 

 One complicating factor is the rather low isoelectric point ( pH 3-4) ; 

 as a consequence, the chromatophore has considerable net charge 

 at neutrality. This appears to be a factor in explaining a net uptake 

 by chromatophores of added cytochrome c (Newton and Newton, 

 1957). 



