Abstract
The X-ray crystallographic structures of photosytem II complexes have recently been clarified at 3.2-3.8 Å resolutions by three groups. This indicates that the PSII research enters a new stage in which the reaction mechanism can be argued on the molecular basis using the PSII protein structures. To understand the molecular mechanism of electron/proton transfers and especially oxygen evolution, however, the structural information by X-ray crystallography is not sufficient, and further information of detailed structures including protonation and H-bonding structures at individual active sites and of their reactions is necessary. Fourier transform infrared spectroscopy (FTIR) is a most suitable method for such a purpose. By detecting light-induced FTIR difference spectra, the molecular-level structures and reactions of cofactors with coupled protein moieties can be selectively obtained. In this lecture, examples of such FTIR analyses of PSII reactions based on the X-ray structures will be introduced focusing on some redox-active cofactors.
