1808 SPECTROSCOPY AND FLUORESCENCE OF PIGMENTS CHAP. 37C 



which they called "bacteriochlorophyll a" (characterized by the 770 niju band); they 

 suggested that upon extraction this pigment is very rapidly converted into "bacterio- 

 chlorophyll b" (= bacterioviridin), characterized by a band at 660 mju. The finding 

 with purple bacteria could be related to the observations of Schneider; Holt and Jacobs; 

 and others, who also noted the oxidation of bacteriochlorophyll in vitro to a green 

 product (cf. chapter 37B); but since the absorption curve of live purple bacteria, 

 given by Seybold and Hirsch, indicated the presence of green cells (cf. below, section 

 6(c)), this contamination may have been the main reason also for their results in vitro. 

 Their finding with green bacteria similarly suggests a contamination of green cultures 

 by purple cells. 



(c) Protochlorophyll and Other Porphin Derivatives 



The absorption spectrum of protochlorophyll, reproduced in Vol. II, 

 Part 1 (fig. 21.8), from Rudolph (1933) and Koski and Smith (1948), was 

 re-determined by Krasnovsky and Vojnovskaja (1949). Absorption peaks 

 were found at G23, 571, 533 and 433 m/x in ether, and at 633, 588, 550 and 

 453 m/x in pyridine {cf. table 21. IV). The transmission minimum of proto- 

 chlorophyll in coats of winter squash seeds was observed at 645-G50 m/x 

 (cf. p. 705). 



Krasnovsky, Kosobutkaya and Voynovskaya (1953) noted that in 

 etiolated leaves the corresponding transmission minimum was located 

 at 635 m/x, and considered this as evidence that protochlorophyll can be 

 present, in vivo, in two forms — an "active" form, "Pchl 635," capable 

 of conversion into chlorophyll in light, and an "inactive" (polymeric ?) 

 storage form, "Pchl 645." (Protochlorophyll in seed coats is not con- 

 verted to chlorophyll by illumination.) This suggestion is analogous to 

 Krasnovsky's hypothesis of the existence of two states of chlorophyll and 

 bacteriochlorophyll in vivo (cf. below, section 66). 



In extension of the observations of Livingston and co-workers, and of 

 Evstigneev et al., on the effect of complexing (with water or organic bases) 

 upon the absorption spectrum of chlorophyll, Livingston and Weil (1952) 



Table 37C.IA 



Complexing Constants (Ki) Calculated from Absorption Changes 

 (after Livingston and Weil 1952) 



Pigment 



Mg-Chlorophyll 

 Activator Mg-porphyrin Zn-porphyrin ( = Chi a) Zn-Chlorophyll 



Aniline 41 — 46 — 



Benzyl alcohol 1 . 120 — 2 . 900 — 



Quinoline 8.300 1800 13.300" 15.200 



Heptylamine 110.000 — 160.000 — 



" Similar value obtained from fluorescence measurements. 



