PHOTOCHEMISTRY OF CHLOROPHYLL in vUrO 11 



separate peaks, and there is apparently a new absorption band in the far red 

 or near infrared. 



Rabinowitch: There seems to be a definite distinction in that metastable 

 (triplet) chlorophyll a has a large band at 475 m/* and only a slight indication of a 

 hand at 525 m/j (or somewhere in that region), while Krasnovskii's reduced chloro- 

 phyll has a very prominent peak at 515 m/i, but at 475 ni/x it shows only a nega- 

 tive effect (decrease in absorption). The ionized (and also perhaps the oxidized") 

 chlorophyll a, as well as the metastable and the reduced form all have a band at 

 515-525 m^, but I think there is a definite distinction between the metastable 

 and the reduced form at 475 m^t. This, I think, is important, particularly in con- 

 nection with what we will report later on the changes in the absorption spectrum 

 of illuminated Chlorella cells. 



Duysens : Mr. Goedheer has made some careful measurements of the polariza- 

 tion spectra of the fluorescence of the chlorophylls, and his interpretation of 

 these measurements is that the Soret band consists of two different bands with 

 transitions perpendicular to each other. There is between the Soret band and 

 the red absorption band of chlorophyll and of bacteriochlorophyll another weaker 

 electronic band, with a transition perpendicular to that of the red absorption band. 



Rabinowitch: Kuhn has assigned one of the weak chlorophyll bands in the 

 green to a different electronic transition. This could not be confirmed at Utrecht. 

 On the other hand, another band in the yellow region appeared to belong to a 

 separate electronic transition. We, too, could not confirm Kuhn's result, and 

 thought that it may have been due to contamination of his chlorophyll with 

 pheophytin, which has a stronger band in the green than chlorophyll. 



Linschitz : We have a flash spectrum which shows a peak for the metastable 

 state somewhat further toward the green, at about 530 m/x. 



Rabinowitch : Do you have a prominent peak at 475? 



Linschitz: We have a suggestion of a shoulder at 475, but we have a higher 

 peak further out toward the green, where Livingston found a somewhat lower 

 absorption. 



{Note added in proof: Since this work was prepared for press, Dr. Linschitz com- 

 pleted a series of careful measurements of the absorption spectra of the chloro- 

 phylls a and b in their triplet state. Chloroph.yll a in its transient state has its 

 main peak at 485 m/x and a lesser peak at 385 mp. The absorption extends 

 throughout the visible, being still appreciable at 750 m/z- There does not appear 

 to be a maximimi near 530 mn, nor on the long wavelength side of the normal red 

 peak. — R. L.) 



References 



1. Freed, S., and Sancier, K. M., Science, 114, 275 (1951); ibid., 116, 175 (1952). 



2. Livingston, R., and Weil, S., Nature, 170, 750 (1952). 



3. Evstigneev, V. B., Gavrilov, W. A., and Krasnovskii, A. A., Doklady Akad. 



Nauk. S.S.S.R., 70, 261 (1950). 



4. Weil, S., Doctoral dissertation, University of Minnesota, Minneapolis, 1952. 



5. Freed, S., and Sancier, K. M., Science, 117, G55 (1953). 

 G. Weller, A., ./. Am. Chem. Soc, 76, 5819 (1954). 



