332 A. II. KRALL 



Gibbs : Do they cliange in concentration with light? 



Krall : If they do, the change is so small that it has not been readily detected, 

 while the change in 5a and 5b is very great. 



Vernon : How have yon shown whether this compound has been oxidized or 

 reduced? All you have shown is that it is present under some conditions and under 

 other conditions it is gone. 



Krall: I assume reductive conditions when oxygen is absent; also that light 

 produces a reductant. 5a might be the oxidant, but it would be rather odd that 

 it would pile up under reductive conditions. Of course, it might be a product of 

 fermentation. 



Rabinowitch: If this is the reduced product for the oxidation reduction system, 

 wouldn't you under the conditions where it is oxidized find another peak, which 

 would belong to the same compound in the oxidized form? 



Krall : I feel that it goes into the 5b peak, but the evidence on that is tenuous. 



Rabinowitch : Could 5a or 5b be anything related to thioctic acid? Has thioctic 

 acid some characteristic absorption band? 



Krall : The oxidized form has a 340-m^ band but I cannot find this band in 5a. 



French : Have you tried any other plants? 



Krall : Algae, corn, tobacco and barley. All contain both 5a and 5b. 



French : In about the same concentrations? 



Krall : The concentration in algae is not as high as in corn and barley. 



References 



1. Bradley, D. F., and Calvin, M., "The effect of thioctic acid on the quantum 



efficiency of the Hill reaction," Arch. Biochim. and Biophys., 53, 99-118 

 (1954). 



2. Gvmsalus, I. C, Dolin, M. I., and Struglia, L., "Pyruvic acid metabolism. 



III. A manometric assay for pyruvate oxidation factor," J. Biol. Chem., 194, 

 849-857 (1952). 



3. Hendley, D. D., and Conn, E. E., "Enzymatic reduction and oxidation of 



glutathione by illuminated chloroplasts," Arch. Biochem. and Biophys., 4^, 

 454-464 (1953). 



4. Khym, J. X., and Cohn, W. E., "The separation of sugar phosphates by ion 



exchange with the use of the borate complex," /. Am. Chem. Soc, 75, 1153- 

 1156(1953). 



5. Krall, A. R., and Burris, II. H., "Evidence for the participation of cytochrome 



oxidase in photosynthetic fixation of carbon dioxide," Physiol. Plantarum 7, 

 768-776 (1954). 



