1826 SPECTROSCOPY AND FLUORESCENCE OF PIGMENTS CHAP. 37C 



go very far beyond what was already described in chapter 21 (part B2); 

 they are summarized in table 37C.IIIB. 



The one remarkable result in table 37C.IIIB is the fluorescence and 

 photochemical activity of chlorophyll colloids prepared with the help of 

 aqueous (cathionic, anionic or neutral) detergents. Presumably they con- 

 tain chlorophyll molecules adsorbed on detergent micelles. Such prepara- 

 tions have absorption bands at 668-670 ran, as compared to 678 mju for the 

 main peak in living leaves. {Cf. section 6(a) below for Krasnovsky's hy- 

 pothesis that leaves contain chlorophyll in two forms, one fluorescent and 

 photochemically active, with an absorption band at 665-670 m.ii, and one 

 nonfluorescent and photochemically inactive, with an absorption band 

 at 677-678 mn.) 



Krasnovsky, Voynovskaya and Kosobutskaya (1952) studied, in a simi- 

 lar manner, the spectra of different preparations of hacteriochloro-phyll and 

 bacteriopheophytin. Solid films, obtained by evaporation of ethereal, 

 acetonic or alcoholic solution of these pigments, showed two absorption 

 peaks — at 800 and 850 (±10) mn, respectively. Heating to 60° C. caused 

 a weakening of the second and enhancement of the first peak; the original 

 relation was restored upon cooling. Condensing water vapor on the film 

 shifted the peak from 850-860 to 870 mju ; when a trace of urea was added 

 to the solution before film formation, condensation of water upon the film 

 sometime shifted the peak to as far as 890 m^t. In some cases, "hydrated" 

 films showed three peaks — at 800, 850 and 890 m/x. 



Various organic compounds (sugar, palmitic acid, glycocoll, yeast, 

 nucleic acid, sulfur, etc.,) introduced into the ethereal solution of bacterio- 

 chlorophyll before evaporation, had no effect on the film spectrum; other 

 additions (hpoids, imidazole, cetyl alcohol) reduced the absorption peak 

 at 850 mju — which Krasnovsky attributed to a state of higher aggregation — ■ 

 while preserving that at 790 ( ± 10) m/x. 



The observation that films obtained from raw methanolic extract of 

 bacteriochlorophyll (transferred into ether and then evaporated) had only 

 one absorption peak (at 780-790 m/x) was attributed to a lipoid impurity 

 carried over from the cell material. 



Bacteriopheophytin films showed a single peak at 850 (±5) m^u; it was 

 not affected by heating to 100° C. 



Colloidal solutions of bacteriochlorophyll were obtained by direct dis- 

 solution in water of the pigment adsorbed on sugar, and by dilution with 

 water of pigment solutions in alcohol, acetone, dioxane or pyridine (usually, 

 7 cc. of solution were diluted by 8 cc. distilled water, and 0.5 cc. of 10% 

 MgCl2 solution was added to stimulate coagulation). Freshly prepared 

 colloidal solutions generally had two peaks (at 800 and 850 ± 10 m^); 

 only one peak (at 800 ran) was present when pyridine was used as solvent. 



