PRIMARY QUANTUM CONVERSION: EPR EVIDENCE 341 



ACKNOW LEDGMENTS 



The authors wish to express their gratitude for helpful discussions with K. 

 Sauer and for the assistance of Miss A. Maksim in performing the experiments. 



REFERENCES 



1. Ingram, D. F. E., Spectroscopy at Radio and Microivave Frequencies . But- 

 terworths, London, 1956. 



2. Low, W., Paramagnetic Resonance in Solids . Academic Press, New York, 

 1960. 



3. Pake, G. E. Paramagnetic Resonance. W. A. Benjamin, Inc., New York, 

 1962. 



4. Ingram, D. J. E., Free Radicals as Studied by Electron Spin Resonance. 

 Butterworths, London, 1956. 



5. Varian Associated Staff, NMR and EPR Spectroscopy. Pergamon Press, 

 New York, 1960. 



6. Androes, G. M., and Calvin, M., Electron paramagnetic resonance in biology. 

 Biophys. J., 2, 217 (1962). 



7. Smaller, B., Electron paramagnetic resonance studies of biological inter- 

 est. Advances in Biological and Medical Physics, (1963). In press. 



8. Randolph, M. L. Quantitative studies of ESR produced in biologically sig- 

 nificant materials by ionizing radiations, p. 249 in Free Radicals in Bio- 

 logical Systems (M. S. Blois, Jr., ed.). Academic Press, Inc., New York, 

 London, 1961. 



9. Calvin, M., and Androes, G. M., Electron paramagnetic resonance in photo- 

 synthetic systems, p. 319 in Studies on Microalgae and Photos ynthetic 

 Bacteria (Japanese Soc. of Plant Physiol., ed.,). Univ. of Tokyo Press, 1963. 



10. Commoner, B., Electron spin resonance studies of photosynthetic systems. 

 p. 356 in A Symposium on Light and Life (W. D. McElroy and B. Glass, 

 eds.). Johns Hopkins Press, Baltimore, 1961. 



11. Androes, G. M., Singleton, M. P., and Calvin, M., EPR in chromatophores 

 from Rhodospirillum nibrum and in quantasomes from spinach chloroplasts. 

 Proc. Nat. Acad. Sci . U. S., 48, 1022 (1962). 



12. Calvin, M., and Androes, G. M., Primary quantum conversion in photosyn- 

 thesis. Science, 138, 867 (1962). 



13. Clayton, R. K., Primary reactions in bacterial photosynthesis. III. Photo - 

 chem. Photobiol., 1,313 (1962). 



14. Loach, P. A., Androes, G. M., Maksim, A., and Calvin, M., Relationship 

 between electron spin resonance signals from photosynthesizing material 

 and the redox level of its environment. Manuscript in preparation. 



15. Weaver, E.C.EPR studies on Chlamydomonas reinhardi . p. 353 in Carne- 

 gie Institution of Washington Year Book, 1961. 



16. TolIin,G.,Sogo, P. B., and Calvin, M., Energy transfer in ordered and un- 

 ordered photochemical systems. Awi. N. Y.Acad. Sci., 74, 310 (1958), 



17. Arnold, W., and Clayton, R. K., The first step in photosynthesis: evidence 

 for its electronic nature. Proc. Nat. Acad. Sci. U. S., 46, 769 (1960). 



