55Mn ENDOR of the S2-State Multiline EPR Signal of Photosystem II: Implications on the Structure of the Tetranuclear Mn Cluster

摘要: We have performed continuous-wave electron paramagnetic resonance (CW-EPR) and spin echo nuclear double (ESE-ENDOR) experiments on the multiline form of S2-state untreated, MeOH-treated, ammonia-treated spinach photosystem II (PS II) centers. Through simultaneously constrained simulations CW-EPR ESE-ENDOR data, we conclude that four effective 55Mn hyperfine tensors (AX, AY, AZ) are required to properly simulate experimental data [untreated MeOH-treated PS centers (MHz): −232, −270; 200, 250; −311, 180, 240; (MHz):  208, 158; −150, −112; 222, 172; −295, −315, −390]. further show these best supported by a trimer/monomer arrangement three Mn(IV) ions one Mn(III) ion. In this topology, MnA, MnB, MnC strongly exchange coupled core (JAB JBC < −100 cm-1) while MnD is weakly (JCD) end trin...