Probing Tyrosine Z• of the Functional Photosystem II at Temperatures Close to the Onset of the S-state Transitions: An EPR Investigation Employing Rapid Scans

The Magnetically-Split Spectra Of The Metalloradical Intermediates S0YZ • And S2,Yz • Collapse Above ∼100 K To The Unperturbed Spectrum Of YZ • (Zahariou Et Al. 2007). We Studied The Spectrum Of YZ •As Well As Its Decay Kinetics Above 100 K In Various S States. In This Report The Intermediate S2YZ •Is Examined. Its Unperturbed Spectrum Appears Distinct From That Of The Stable YD • Radical. The Spectrum Of YZ • Was Simulated By Varying The Rotational Conformation Of The Phenoxyl Ring And The Spin Density p On Carbon C1. The Latter Can Be Related To The Strength Of The Hydrogen Bond Between Tyrosine And Its Base Partner (Presumably D1 His190).