1752 CHLOROPLASTS, CHROMOPLASTS AND CHROMATOPLASM CHAP. 37A 



Chiba (1954) obtained similar crystals from centrifuged chloroplast 

 material (consisting mainly of grana) rather than from whole cell macer- 

 ates, thus reducing the chance of participation of proteins not connected 

 with chlorophyll in the natural state. He separated the crystalline mate- 

 rial chromatographically into a blue-green and a yellow-green fraction 

 (both separately crystallizable), which he considered as containing the 

 a and h component of chlorophyll, respectively. 



(c) Is All Chlorophyll in the Cell in the Same State? 



In Chapter 14 (pp. 392-393) and Chapter 23 (p. 818) we mentioned 

 Seybold and Egle's suggestion that chlorophyll is present in the cell in two 

 different phases — a non-fluorescent (adsorbed?) phase responsible for most 

 of the light absorption, and a strongly fluorescent (dissolved) phase re- 

 sponsible for the weak average fluorescence. It was argued there that the 

 mutual position of the fluorescence and the absorption peaks in vivo makes 

 this hypothesis implausible. To this, it was suggested that the fluorescence 

 band in vivo may be distorted by reabsorption, shifting its peak toward the 

 longer waves; but in this case, dilute cell suspensions should show a shift 

 of the fluorescence band back toward its position in solution, which does 

 not seem to be the case. 



Suggestions that chlorophyll (meaning chlorophyll a) may be present 

 in cells in at least two different forms, have since been renewed. Duysens 

 (unpublished) saw an analogy between the absorption spectrum of chloro- 

 phyll in algae and that of bacteriochlorophyll in bacteria. Nothing like 

 the two or three separate infrared peaks shown by bacteria appears in the 

 spectra of green cells; but the main absorption band of chlorophyll a in 

 the red is broadened more than the corresponding fluorescence band^ — 

 too much to be accounted for by the "sieve" and "agglomeration" ef- 

 fects analyzed in Chapters 22 (p. 672) and 37C, section 6a. This can be 

 considered as evidence of overlapping of two absorption bands — provided 

 it is assumed that the potential curves of the ground state and of the lowest 

 excited state of chlorophyll are equally affected by association with proteins 

 and the dense packing of pigment molecules (causing the shapes of the ab- 

 sorption and the fluorescence band to be changed in the same way). The 

 resonance between closely packed pigment molecule should affect the po- 

 tential curves of the excited state stronger than that of the ground state; 

 the absorption band can be therefore affected differently from the fluores- 

 cence band. 



Krasnovsky and Kosobutskaya (1953) observed a shift in the absorption 

 peak, during the greening of etiolated leaves, from 670 to 678 m/i, and a 



