MEASUREMENTS OF ABSORPTION SPECTRA OF PIGMENTS 1807 



calculated the concentration of the latter from French's absorption data 

 (c/. fig. 21.21) and derived in this way a value for the maximum (decadic) 

 absorption coefficient (^max. = 9.6 X 10^ 1. mole~^ cm.~0 in the peak of 

 infrared band of bacteriochlorophyll. Absolute measurement by Holt 

 and Jacobs confirmed this calculation. (They found a:,nax. = 9-5 X 10* 1. 

 mole~^ cm.~'.) 



The position of the peak of the main short-wave band of bacteriochloro- 

 phyll, which we assume to be analogous to the^Soret band" of chlorophyll, 

 could be given previously only as <400 mju (c/. fig. 21.6). It has since 

 been determined by Manten (1948) as 362 m/x (in methanol), by Weigl 

 (1953) as 358 m/x (in ether or acetone), 362.5 mn (in benzene), or 364 m^u 

 (in methanol) and by Holt and Jacobs (1954^) as 356 m^u (in ether). A 

 satellite band appears at 390-400 m/x (392 m/x in ether). The variable 

 relative intensity of this long-wave satellite reminds one of the behavior 

 of the short-wave satellite of the main blue-violet band in chlorophyll 

 (cf. Part 1 of Vol. H, p. 646). 



According to Weigl (1953) the absorption peaks of baderiopheophytin 

 lie, in ether, at 750 mju (amax. = 6.3 X 10* 1. mole"^ cm.~0> 680 mju, 

 620 m/x, 525 m/n, 384.5 m^ and 357 m/x. 



Barer and Butt (1954) confirmed the earlier observations (cf. pp. 618- 

 619) that the red absorption band of haderioviridin, extracted from green 

 sulfur bacteria, lies at 664 m/x — quite close to that of chlorophyll a; they 

 found the same to be true of the main violet band, at 434 m/x. Neverthe- 

 less, on the basis of chromatographic behavior and minor spectroscopic 

 characteristics, Barer and Butt agreed with the suggestion (p. 619) that 

 bacterioviridin is not identical with chlorophyll a. Larsen (1953) gave 

 an absorption curve of an acetonic extract from Chlorobium thiosulfato- 

 philum, showing two sharp main peaks, at 435 and 660 m/x, respectively; 

 and minor bands at 770 (very weak), 625, 496, 467, 412, 392 (shoulder), 

 and 338 m/x; those at 496 and 467 probably indicate the presence of 

 carotenoids. Again, the main bands almost coincide with those of chloro- 

 phyll a, but the minor bands have different positions. 



Whether the much wider shift of the red band toward the longer waves, 

 found in green bacteria (as compared to algae), is due to a difference in 

 the chemical structure of the two pigments, or to a different state of 

 aggregation (or binding to a different protein-lipoid complex), remains to 

 be established. The shift is similar to that found for bacteriochlorophyll 

 in purple bacteria. 



The divergent results of Seybold and Hirsch (1954) already were noted in chapter 

 37.B. These observers found, in extracts from what they called "purple spirillae," 

 as well as in those from green bacteria (Microchloris), absorption bands at both 770 

 and 660 m/x, and contended that green and purple cells carry one and the same pigment, 



