LIGHT‐INDUCED ABSORBANCE CHANGES IN CELL‐FREE EXTRACTS OF NEUROSPORA CRASSA*

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Abstract
Abstract— The mycelium of Neurospora crassa was ground and extracted with buffer and separated into a soluble supernatant fraction and a particulate fraction by centrifugation. Both fractions were examined for light‐induced absorbance changes. Irradiation of the supernatant fraction caused a reversible photooxidation of cytochrome c which was inhibited by sodium azide or by dialysis. The action spectrum for the photooxidation showed that the response was mediated by an endogenous flavin. The photooxidation of cytochrome c, lost by dialysis, could be restored by adding flavin mononucleotide. Irradiation of the particulate fraction with blue light caused a reversible photoreduction of cytochrome c and cytochrome oxidase and, in some samples, of cytochrome b as well. The supernatant fraction showed photooxidation of cytochrome c rather than the more usual photoreductive changes because of the presence of super‐oxide dismutase activity.