Abstract
We studied the temperature dependence of the S1YZ •, S2YZ •, S0YZ •(+MeOH) and S2YZ •(+MeOH) metalloradical EPR signals in the temperature range 4.2–240 K, using slow and rapid scans. As the temperature increases the spectra narrow progressively and above 100 K collapse to a “25 G” signal somewhat broader than “signal II”. The spectra do not reach saturation at microwave powers up to 100 mW over the entire temperature range, and the signal intensity multiplied by temperature remains approximately constant. The narrowing of the SnYz • EPR signals is consisted with an increase of the Mn spin-lattice relaxation rate, with increasing temperature. We conclude that the broad EPR signals observed at low temperatures and the narrow signals at elevated temperatures are manifestations of the same intermediate SnYz • (n = 0, 1, 2) and the high temperature spectrum is due to Tyr Z• unperturbed by the magnetic interaction with Mn.
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Zahariou, G., Ioannidis, N., Sioros, G., Petrouleas, V. (2008). The Progressive Exchange-Narrowing of the S0YZ •, S1YZ •, and S2YZ • Spectra Reveals the Unperturbed Spectrum of Tyr Z• in Oxygen Evolving PSII Preparations: A Rapid Scanning EPR Investigation in the Temperature Range 4.2–240 K. In: Allen, J.F., Gantt, E., Golbeck, J.H., Osmond, B. (eds) Photosynthesis. Energy from the Sun. Springer, Dordrecht. https://doi.org/10.1007/978-1-4020-6709-9_123
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DOI: https://doi.org/10.1007/978-1-4020-6709-9_123
Publisher Name: Springer, Dordrecht
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