719 



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Edgar Inselberg and J. L. Rosenberg 



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 A 



A-B 



'650 700 750 800 



WAVELENGTH - m^ 



850 



Fig. 3. Spectra of the negative changes in live and 

 killed Porphyridium. Two pictures of flash plus mea- 

 surilrig li^t and one flash-only picture vrere taken at 

 each wavelength. C\irve A: live Porphyridium. Curve B: 

 killed Porphyridium. 



inith Porphyridium in 0.1 M NaHCO^, is shown in Pig. 3, A. The 

 sample was excited vrith li^t transmitted by a Coming U-72 fil- 

 ter (335 - 630 m|i.). Several shallow maxima can be observed, but 

 no predominant change in the vicinity of 700 my. (cf. Ref, 3, p. 

 32U). The half-life of the change at 703 mix was found to be 1.6 

 milliseconds . 



The spectrum was then obtained witbi killed Porphyridium, in 

 order to evaluate its suitability as a blank. An aliquot of the 

 same sample used to obtain Spectrum A of Fig. 3 was placed in a 

 boiling water bath. Dui'ing the first UO minutes at 100", the mag- 

 nitude of the 703 mix change remained essentially the same as in 

 live Porphyridium, which suggests that the change may be non- 

 enzymatic in live Porphyridium as well. After two hours in the 

 water bath, Porphyridium maintained about one half of its initial 

 activity. The spectrum in killed Porphyridivun (tvfo hours at 100*) 

 adjusted to essentially the same absorbance as live Porphj^ridium 

 at 703 mjx is presented in Fig. 3, B; A - B, the difference be- 

 tween the spectra for live and killed Porphyridium, is a3.so 

 shown. The above spectra, if interpreted as absorption changes, 

 woxiLd suggest a non-specific, purely photochemical bleaching. 



