SPECTRA OF CRYSTALLINE AND COLLOIDAL PIGMENTS 



1819 



>10-« mole/1. Ca + +— has a very high optical density, and a red band 

 shifted as far as 735 m^. The red band of monolayers obtained from 



.000 



400 



500 600 700 



WAVE LENGTH (M/i) 



Fig. .37C.19. Absorption spectrum of ethyl chlorophyllide a monolayer on 

 water (after Jacobs, Holt and Rabinowitch 1954). Dashed line, solution; solid 

 line, monolayer. Ordinate: optical density of a single monolayer. 



400 450 500 550 600 650 

 WAVELENGTH IN MU 



700 750 



Fig. 37C.20. Absorption spectra of chlorophyll a monolayers (after Jacobs e< al. 

 1953). Dots, "compressed gas" or "colloidal" type monolayer (prepared without 

 Ca + + ions); circles, "crystalline" monolayer (prepared in the presence of Ca + + ions). 

 Ordinate, optical density of a single monolayer; arrows, location of absorption peaks m 

 solution. 



Ca++-free solutions is located at 670 m/x; their optical density in this band 

 is much lower {cf. table 37C.III). 



According to Hanson (cf. Vol. I, p. 448), chlorophyllide crystals consist 



