1850 



SPECTROSCOPY AND FLUORESCENCE OF PIGMENTS CHAP. 37C 



scattering (indicated by the higher ratios of the optical densities in the 

 absorption peaks and the troughs between them). 



Except for increased sharpness, the infrared absorption bands of the 

 purple bacteria, measured by Barer, are similar to those observed earlier 

 by the Dutch investigators; they, too, show two or three peaks of varying 

 relative intensity. Barer suggested that the 585-590 mju absorption 

 band (cf. figs. 22.27 and 37C.29) is correlated with the band in bacterio- 

 chlorophyll solutions located, depending on the solvent, between 575 and 

 610 m/i {cf. section 2(&) of this chapter). On p. 704, it was suggested that 



370 410 450490 530 570 610 750 790 830 870 910 



Fig. 37C.29. Absorption spectra of Rhodopseudo- 



monas spher aides (A) in the absence of iron, (B) 



in the presence of iron. Absorption spectrum of 



Rhodospirillum rubrum (C) (Barer 1955). 



this solution band has no counterpart in vivo; Barer's interpretation 

 implies that such a counterpart does exist, but that, in contrast to the two 

 other main bands, it is not significantly shifted towards the longer waves. 

 For comparison, the main near-ultraviolet band of bacteriochlorophyll is 

 visible, on Barer's absorption curves of purple bacteria, at 375 m^, indicat- 

 ing a shift by 1500 cm.~^ from its position in ethereal solution (at 356 mju, 

 cf. section 2(b) above); while the long-wave band is shifted by 500-2000 

 cm.~^ (assuming that all three peaks, at about 800, 850 and 890 m/z, corre- 

 spond to the one solution band at 770 m/x). 



Similarly to French's two differently colored vaiieties of Streptococcus varians, 

 mentioned on p. 707, Barer obtained, from the same inoculum, two strains of Rhodo- 

 pseudomonas spheroides, with the spectra shown in fig. 37C.30. The red variety is 

 characterised by peaks at 550 (weak), 512, 477, and 450 m/x; the green one, by peaks 

 at 490, 460, 425 and 405 m^. Duysens (1952) found a difference between the absorption 



