HAEM PROTEIN CONTENT AND FUNCTION IN RELATION TO STRUCTURE 279 



However, despite the many researches, particularly on chloroplast 

 development, emphasis has been mainly on morphology. Few chemical 

 analvses at the molecular level ha\e been performed. Xo structural studies 

 have been conducted simultaneouslv with exhaustive molecular analyses. 

 The development of the bacterial chromatophore system, the study of 

 which is just beginning [9, 10], may pro\ide a well-defined test system for 

 future research. 



There is one study available on molecular composition as a functi(Mi 

 of fragmentation. While the data are incomplete in many respects, they are 

 sufficient, taken together with gleanings from various other researches in 

 the literature, to base a \alid discussion of possible relations between 

 molecular composition and the primary processes in photosynthesis. 



These data were obtained by Xewton and Newton in our laboratory 

 three years ago and are concerned w ith the composition of the photoactive 

 sub-cellular particles derived by various fragmentation procedures from 

 the obligate photo-anaerobe, Chyomatiiun [11]. The gross composition and 

 characterizations of some components of chromatophores and chromato- 

 phore fragments, as isolated by differential centrifugation, were studied. 

 Qualitative kinetic analyses of the progressive fragmentation of cells into 

 small subcellular aggregates were conducted, together with molecular 

 analyses for each fraction. 



I have recast these data so as to summarize briefly the essential results 

 in a single table (Table I). These data may be expanded by borrowing 

 some figures from other researches. 'I'hus, Lester and Crane [12] give a 

 figure of 2-9 jxM Coenzyme "Q7" (or "ubiquinone" [13]) per g. dry 

 weight of cells. This approximates to ^0-5 /xM per g. wet weight of 

 chromatophores, a relatively great quantity of this benzoquinone. For 

 R. rubniin, a somewhat higher but comparable figure is given, the quinone 

 found being "Q,, " and the concentration approximately twice that of the 

 Chrojfuit/ 1(1/1 "();". 



Inasmuch as all the ph(jtoactive structures known are supposed to be 

 self-duplicating units, it can be expected that nucleic acids are present. 

 As seen in Table 1, acid-soluble nucleotides are found and in addition 

 there is residual phosphate which is associated with protein and with 

 insoluble nucleic acid. A reasonable treatment of these data indicates that 

 out of the total P present (85 [.im) probably no more than 20 /tM can be 

 ascribed to nucleic acid. This can be contrasted with the nucleic acid P 

 content of chromatophores originally obtained from R. ruhruni by Schach- 

 man, Pardee, and Stanier [14], who found for the same protein content a 

 value of ~ 200 /tM. 



Of course it is not surprising that large variations in content of par- 

 ticular fractions will occur as the source of particles is varied. This is true 

 of all fractions examined to date such as the chlorophylls [15], the caro- 



