title: A new EPR signal associated with photosystem 1 of algal and plant photosynthesis.
abstract: A new low temperature electron paramagnetic resonance (EPR) signal with a g-value of 1.97 was found in Photosystem-1 particles from a blue-green alga, Anacystis nidulans, illuminated at room temperature. A similar signal was also found in spinach Photosystem-1 particles treated with thiophenol to decrease interference from a signal due to Center A. In the dark, the signal appeared only when the Anacystis particles were at redox potentials lower than -0.5 volts where Centers A and B were also reduced. The signal is most likely due to another iron-sulfur cluster, tentatively designated as Center C. Center C could be photoreduced at low temperatures like Center A when Centers A and B were partially reduced prior to illumination, indicating possible close association of these centers in Photosystem 1 of green plant and algal photosynthesis.
mesh_terms: D000458:Cyanobacteria / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D007506:Iron-Sulfur Proteins / Q000502:physiology; D010084:Oxidation-Reduction; D045322:Photosynthetic Reaction Center Complex Proteins; D010940:Plant Proteins / Q000378:metabolism*; D010944:Plants / Q000378:metabolism*; D013696:Temperature
chemical_list: D007506:Iron-Sulfur Proteins; D045322:Photosynthetic Reaction Center Complex Proteins; D010940:Plant Proteins