Phytochrome is consistently observed in pellets centrifuged from homogenates of etiolated, 5-day-old oat seedlings. The majority of pigment associated with the pellet cannot be removed by buffer washes, nor can appreciable quantities of additional phytochrome be adsorbed onto the sedimented material. Over 70% of phytochrome in the pellet is released by 1% Triton X-100.Storage at 0 degrees , irradiation by white light, and Triton treatment all cause much greater loss of photoreversibility in pelleted phytochrome than in supernatant phytochrome. We conclude that the phytochrome in the 1500 to 40,000g (30 min) pellet is distinct from the soluble phytochrome in the supernatant.

Journal Article↗

PubMed1969

Photosynthetic Light Reactions in Chemically Fixed Anacystis nidulans, Chlorella pyrenoidosa, and Porphyridium cruentum.

The photochemical activities of various species of unicellular algae (Anacystis nidulans, Chlorella pyrenoidosa, and Porphyridium cruentum) were studied following chemical fixation. Fixation with formaldehyde and glutaraldehyde yielded cells which retained their ability to perform photosystem I and photosystem II reactions. The photochemical efficiencies of some fixed algae are as great as those of unfixed spinach chloroplasts. Fixed algae containing accessory pigments appear to be useful models for further studies of the light reactions of photosynthesis.

Journal Article↗

PubMed1969

Action Spectra for Photosystems I and II in Formaldehyde Fixed Algae.

Action spectra were obtained for photosystems I and II in chemically fixed algal cells and for photosystem I in unfixed lysozyme treated cells. Untreated algal cells yielded neither of the 2 light reactions with the reaction mixtures used. The action spectra for photosystem I in the blue-green alga Anacystis nidulans and red alga Porphyridium cruentum follow the absorption spectrum of chlorophyll a with a small peak in the region of the accessory pigments. In the green alga Chlorella pyrenoidosa the photosystem I action spectrum follows the absorption spectrum of chlorophyll a. Photosystem II action spectra in A. nidulans and P. cruentum follow the absorption spectra of the accessory pigments while that in C. pyrenoidosa is shifted slightly toward the blue spectral region. These results provide additional evidence that formaldehyde fixed cells are valid models for studying the light reactions of photosynthesis.

Journal Article↗

PubMed1969

Photosynthetic light reactions in chemically fixed spinach thylakoids.

After proper fixation with glutaraldehyde, spinach thylakoids retain both photosystem I and photosystem II activity. The photochemical activity of fixed thylakoids is highly resistant to 1% triton. This indicates that fixed thylakoids may be useful starting material for isolation of functional components which can be related to the original structure of the membrane.

Journal Article↗

PubMed1969