654 



ABSORPTION SPECTRA OF PIGMENTS IN VITRO 



CHAP. 21 



The relatively strong absorption of the crude extract in the violet may be 

 due to the presence of yellow pigments ; its stronger absorption in the far 

 red (>700 m^u) was attributed by Smith to scattering. However, in- 

 creased absorption in the far red has also been observed by Noddack and 



2.0 



O 



(a) Phosphate buffer,^ 

 pH6.6, 1/15 M 



n — -| — r — I — I — r 

 820 860 900 940 



WAVE LENGTH, m/i 



1.5 



o 

 o 



(c) Culture medium No. 231 



1.6 



740 



1.4 



— 1 — r" — I — I I 

 860 900 940 



{b) Distilled water 



740 



1 r 



780 820 



T 1 — r — i — I — r 



860 900 940 



WAVE LENGTH, m/i 



(.d) I. Cells in distilled 

 water 

 2. Alcoholic extract 



740 



780 820 



wavE LENGTH, m/i 



— 1 — I — r 

 900 940 



780 820 



WAVE LENGTH, vnfi 



Fig. 2 1.30 A. Comparative absorption spectra of cell suspensions and pigment ex- 

 tracts of strain D purple sulfur bacteria in different media (after Katz and Wassink 

 1939). Curve 1, cells; curve 2, extract. See page 656. 



Eichhoff in Chlorella suspensions (see fig. 22.21), although these investiga- 

 tors used an integrating method, which w^as supposed to give true absorp- 

 tion values, free of scattering effects. 



Rabideau, French and Holt (1946) gave absorption curves (obtained 

 with an Ulbricht sphere) and transmission curves (obtained with a Beck- 

 man spectrophotometer) for chloroplast dispersions prepared by means 



