618 



ABSORPTION SPECTRA OF PIGMENTS IN VITRO 



CHAP. 21 



violet bands of chlorophyll a, respectively (the whole system having been 

 shifted by about 60 m^t toward shorter waves), while the band in the near 

 infrared has no analogue in the spectrum of ordinary chlorophyll. 



The status of the "orange" bacteriochlorophyll band needs additional 

 clarification. Our interpretation is based on figure 21.6. A strong band 

 on the short-wave side of the main red band is also recognizable in the spec- 

 trum of bacteriopheophytin as observed by French (fig. 21.21), but is 

 situated much further toward the green, at 530 m^; in addition, there is a 

 weaker band at 680 m/x and indications of a still weaker one at about 630 

 m/n. Dutch observers state (see page 702, chapter 22) that "alcoholic 



1.0- 



r;0.5- 



c 

 o 

 u 



620 640 660 680 700 



WAVE LENGTH, m^ 



720 



Fig. 21.7. Red absorption bands of al- 

 coholic extracts of (1) green alga, Chlo- 

 rella, (2) green sulfur bacteria, and (3) a 

 blue-green alga, Oscillaloria (after Katz 

 and Wassink 1939). 



Q. 



to 



200 



700 



300 400 500 600 

 WAVE LENGTH, m^ 



21.8. Absorption spectrum of 

 protochlorophyll after Rudolph (1933) 

 in the insert, and after Koski and Smith 

 (1948) in the main figure. 



Fig. 



extracts from purple bacteria show only one absorption maximum at 774 

 m/x," but it is not certain how wide a region this statement is supposed to 

 cover. The extract absorption curves in figures 21.30A and B extend only 

 down to 730-740 m/x. 



One question to be clarified is the possible contribution to the ab- 

 sorption curves of bacteriochlorophylls of derivatives analogous to chloro- 

 phylls h, c and d. The existence of pigments of this kind was suggested by 

 Seybold and Egle (1939) (cf. Vol. I, page 407), who gave some provisional 

 figures for the positions of their absorption bands. 



The absorption spectrum of bacterioviridin — the pigment of green bac- 

 teria (cf. Vol. I, page 445) — was observed bj'' Metzner (1922) and, more 

 recently, by Katz and Wassink (1939). Apparently, it is very similar to 

 that of chlorophjdl a. Figure 21.7 shows the red adsorption band in 



