Reaction Mechanism of the Terminal Plastoquinone Q in Photosystem II as Revealed by Time-Resolved Infrared Spectroscopy.

The secondary plastoquinone (PQ) electron acceptor Q in photosystem II (PSII) undergoes a two-step photoreaction through electron transfer from the primary PQ electron acceptor Q, converting into plastoquinol (PQH). However, the detailed mechanism of the Q reactions remains elusive. Here, we investigated the reaction mechanism of Q in cyanobacterial PSII core complexes using two time-revolved infrared (TRIR) methods: dispersive-type TRIR spectroscopy and rapid-scan Fourier transform infrared spectroscopy.

Syntheses, structures, and magnetic properties of a series of Mn-M-Mn trinuclear complexes with different spin configurations.

A series of trinuclear complexes, [MnII2Y(L)(HL)(NO)][Y(NO)]·7HO (1'), [MnII2Gd(HL)(NO)][MnII2Gd(L)(HL)(NO)][Gd(NO)]·2(-Xy)·12HO (2') and [MnII3(L)(HL)(NO)](NO)·1.25(-Xy) (3'), were synthesized using a β-diketone ligand HL (HL = 1,3-bis(pyridin-2-yl)propane-1,3-dione). X-ray structural analyses revealed that each complex has a trinuclear core with an Mn(II)-M-Mn(II) arrangement (M = Y (1), Gd (2), and Mn (3)).