Relaxation behaviour of the tyrosine Y-D radical in photosystem II: evidence for strong dipolar interaction with paramagnetic centers in the S-1 and S-2 states
Inversion recovery (T-1) and microwave power saturation studies have been performed, between 4 and 25 K, on the EPR signal from the stable tyrosyl radical, Y-D(.), in photosystem II core complex preparations from higher plants. Measurements are reported from the dark stable S-1 and first turnover S-2 states of the photosystem catalytic Mn cluster and in two cryoprotectant regimes; sucrose and ethy