ABSORPTION SPECTRA OF THE PHYCOBILINS 667 



(1930) himself noted that the specific extinction of the phycobiHns is ten 

 times stronger than that of hemoglobin — while his analysis indicated the 

 presence of only one half mole pigment per Svedberg unit of protein in 

 phycobilins, as against one mole pigment per unit of protein in hemoglobin. 

 If Lemberg's analysis is in error, and the content of phycobilins in the 

 chromoproteids is as high or even higher than that of hemin in hemoglobin, 

 the molar extinction coefficients of the phycobilins, given in Table 21, X 

 will have to be proportionally reduced. 



Table 21. X 



Estimated Molar Extinction Coefficients of Phycobilins 

 (in the Band Maxima) 



« L = Lemberg (1928, 1930). S,K = Svedberg and Katsurai (1929). 



A comparison of the intensity of the phycocyanin band at 615 m/x with that of the 

 chlorophyll band at 680 m/Li in the absorption spectrum of live Oscillatoria cells (cf. fig. 

 22.18) leads to similar doubts concerning Lemberg's analytical data. According to 

 Lemberg (1928), the content of the chromoproteids in algae (determined with another 

 species, Ceramium rubrum) is of the order of 0.5%, with only 2% chromophore in the 

 complex. This corresponds to as little as 0.01 % phy cobilin in the dry matter of the algae 

 — while the concentration of chlorophyll in red algae usually is of the order of 0.1% {cf. 

 Table 15.11, Vol. I). The predominance of the phycocyanine band over the chlorophyll 

 band in figure 22.18 therefore leads to the improbable conclusion that the molar extinc- 

 tion coefficient of the phycobilins is at least ten, and perhaps one hundred, times higher 

 than that of chlorophyll — unless we prefer to assume that Lemberg's analytical figures 

 are too low. 



In addition to the fact that the estimate of the chromophore content in the complex 

 (~2%) is probably too low, the content of the chromoproteid in the algae (~0.5%) 

 may also have been underestimated {cf. chapter 15, page 418). 



