PHYSICAL AND CHEMICAL PROPERTIES PROTOCHLOROPHYLL HOLOCHROME 337 



5. Goedheer, J. C, "Optical Properties and In Vivo Orientation of Photo- 

 synthetic Pigments". Drukkerij Gebr. Janssen-Nijmegen, Utrecht (1957)- 



6. Forster, Th., " Fluoreszenz Organischer Verbindungen". Vandenhoeck and 

 Ruprecht, Gottingen (195 1). 



7. Latimer, Paul, and Smith, J. H. C, Yearb. Carneg. Instn. 57, 293-295 (1958)- 



8. Goedheer, J. C, and Smith J. H. C, Yearb. Carneg. Instn. 58, 334-336 (i959)- 



9. Goedheer, J. C, and Smith, J. H. C, unpublished. 



10. Kendrew, J. C, et al. Xatiire, Lond. 185, 422-427 (i960). 



11. Wyman, Jeffries, Jr., Advanc. Protein Chem. 4, 410-531 (1948). 



12. Cohn, E. J., and Edsall, J. T., "Proteins, Amino Acids, and Peptides". 

 Reinhold Publishing Corp. 445 (i943)- 



13. Stracher, X.,J. biol. Chem. 235, 2302-2306 (i960). 



14. Fromageot, Claude, and Schnek, Georges, Bioclmn. biopliys. Acta 6, 114-122 



(1950)- 



15. McLeod, G. C, and Coomber, J., Yearb. Carneg. Instn. 59, 324. (i960). 



16. Granick, S., J. bin/. Chem. 175, 333-342 (1948). 



Discussion 



Goodwin: It doesn't appear that carotenoids play any important part in the 

 normal transformation of protochlorophyll into chlorophyll. I was wondering if 

 thev can play a part if required. In other words have you run an action spectrum 

 for this transformation and can the carotene-absorbed light be used ? 



Smith : Actually the carotene-absorbed light is a hindrance, because it acts as a 

 screen. When you run the action spectrum you find that it is exactly the absorption 

 spectrum of protochlorophyll in the albino leaf, and in a normal leaf which contains 

 large amounts of carotenoids the peak in the violet is ver\' low compared to the 

 peak in the red. But the action spectrum in an albino plant is very high in the 

 violet as compared to that in the red, so consequently the carotenoids actually act 

 as a screen. 



Chanxe: Since you appear to have one chlorophyll per particle do you then 

 consider that you have a heterogeneous distribution of particles or two separate 

 bonds on a single particle ? 



Smith: We presume a distribution of particles and this is probably right 

 because otherwise you would expect the transfer of energy, once it is absorbed, 

 through the whole protein to carry on the transformation, but since there are 

 discrete particles and these particles are 80 to 100 A in diameter you can't get 

 energy transfer very well between the particles. 



K.^MEN : How do you conceive the process of chlorophyll formation ? 



Smith: I wish we knew the answer to that question. I pointed out that you 

 have a change in the absorption spectrum of chlorophyll in the plant after it is 

 formed. We are thinking that perhaps it is formed on one protein and transferred 

 to another, but it must go onto the same protein molecule or else you would not 

 get the increase in depolarization that you do. If it went onto separate molecules 

 you wouldn't get this depolarization linear with concentration, but since you do 

 get that you are piling them up on the same protein molecule, and the explanation 

 that we have of this is that owing to the change in absorption spectrum and owing 



VOL. II. — z 



