The Absolute Quantum Yields of Fluorescence of 

 Photosynthetically Active Pigments* 



PAUL LATIMER, THOMAS T. BANNISTER, and EUGENE I. 



RABINOWITCH, Photosynthesis Research Project, Department of Botany, 



University oj Illinois, Urbana, Illinois 



Knowledge of the fluorescence yields of photosynthetically active 

 pigments is important for the understanding of their photochemical 

 activity and the probability of resonance energy transfer between 

 these molecules in the hving cell. We have measured the absolute 

 quantum yields of fluorescence of chlorophyll a, ethyl chlorophyllide 

 a, phycocyanin and phycoerythrin in solution, and of chlorophyll 

 a and phycocyanin in the living cell, using the integrating sphere 

 techniciue (1). 



Prins (2) found the quantum yield of fluorescence, ^, of chlorophyll 

 (a + 6?) in solution to be about 10%, whereas Forster and Livingston 

 (1) found that of chlorophyll a to be about 25%. Wassink and co- 

 workers (3,4) reported, for chlorophyll in various organisms, cp values 

 of 0.1% to 0.3%. Arnold and Oppenheimer (5) estimated, for phy- 

 cocyanin in solution, <p ~ 20%, and in the living cell, about 1.5%. 

 Duysens (6) suggested that the methods used by Wassink et al. and 

 by Arnold and Oppenheimer to determine the total fluorescence from 

 the observed sample were unsatisfactory. He estimated that their 

 measurements actually indicate that <p of chlorophyll in green cells 

 is about 1%, and <p of phycocyanin in blue-green cells, about 5%. 

 His arguments suggest that the yield of phycocyanin in solution may 

 be as high as 65%. 



Pure chlorophyll a and chlorophyllide a were prepared by Dr. A. S. 

 Holt. Phycocyanin (from Sijnechocystis) and phycoerythrin (from 

 Povphyridium) were purified chromatographically on tricalcium 

 phosphate columns, approximately as described by Haxo, O'hEocha, 



* This work was carried out with the assistance of the Office of Naval Research. 

 The paper is based on a dissertation submitted by Paul Latimer in partial 

 fulfillment of the requirements for the degree of Doctor of Philosophy in the 

 Graduate College of the University of Illinois, 1956. 



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