C. STACY FRENCH 73 



the epidermis wet with methanol after extraction of the chlorophyll. 

 In comparison with this is also drawn as a dotted line the fluorescence 

 spectrum of uroporphyrin- 1-octamethyl ester showing a rather close 

 agreement. The fluorescence spectrum of a solution of the pigment in 

 hydrochloric acid also agreed with that of a hydrochloric acid solution 

 of this porphyrin. 



Now it is well known that porphyrins generally have a very intense 

 absorption band in the blue part of the spectrum known as the Soret 

 band. The trace amounts of this new fluorescent pigment material and 

 its insolubility made it impossible to measure its absorption spectrum. 

 However, the effect of various wavelengths in exciting fluorescence of 

 the pigment in epidermal peels was measured. This action spectrum 

 showed points of equal height at about 405 and 410 m/x and dropped 

 to lower values on both sides. By interpolation it was found that the 

 Soret band of this pigment whose absorption could not be measured 

 directly is at 408 m/*. 



ACKNOWLEDGMENTS 



Extended collaboration with Drs. Violet K. Young, James H. C. Smith, 

 and Hemming I. Mrgin produced most of the results here described. Shorter 

 periods of investigations with Drs. Robert Hill and Glenn Todd opened 

 up new aspects of the field. The electronic components of apparatus were 

 designed and constructed by Messrs. Bertram G. Ryland, Hemy G. Fatten, 

 Jr., George H. Towner, and Dr. Donald R. Scheuch. The mechanical parts 

 ,of the monochromators were built by Mr. Frank Schuster. The replica trans- 

 mission grating was made available by Professor R. W. Wood, and the 

 original reflection grating by Mr. Harold Babcock. 



References 



Carnegie Institution of Washington Year Books: 1948, No. 47, 96-97; 1949, 

 No. 48, 93-94; 1950, No. 49, 86-88, 99-100; 1951, No. 50, 122-123; 

 1952, 51, 153-154; 1953, No. 52, 153-157. 



Duysens, L. N. M. 1951. Transfer of Light energy within the pigment sys- 

 tems present in photosynthesizing cells. Nature, 168, 548. 



Duysens, L. N. M. 1952. The transfer of excitation energy in photosynthesis. 

 Thesis. Utrecht. 



