Flash Spectroscopy of Porphyridium

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Abstract
The spectrum of flash-induced absorption changes in Porphyridium cruentum, a red alga, was similar to Duy sens''steady-state difference spectrum. The major peak, a negative change at 420 m[mu], was attributable to the photo-oxidation of cytochrome f or a similar cytochrome. A smaller positive peak at 450 m[mu], associated with cytochrome, as also observed. A positive change at 395 m[mu], attributed to cytochrome, decayed with a significantly shorter half-life than that at 420 m[mu]. A tentative explanation is advanced. A statistically significant positive absorption change was observed at 520 m[mu]. The relative absorbance change, [DELTA]A/A680 = 2.4 X 10-4, the half band width, 26 mu, and the half-life of the back reaction, 11 milliseconds, closely compare with values obtained by the authors or other investigators for the 515 m[mu] pigment in Chloreila. These results suggest that the 520 m[mu] pigment system performs a similar function in the photosynthesis of green and red algae.