Abstract
The three dimensional structures of the photosystem II (PSII) complexes have recently been clarified by X-ray crystallography at 3.7-3.8 A resolution. For understanding the mechanism of various electron-proton transfer reactions performed in PSII, however, more detailed structural information in active sites like hydrogen bonding and protonation structures, which are often unavailable by X-ray crystallography, is crucial. Fourier transform infrared spectroscopy (FTIR) is a suitable method to detect such detailed structures and interactions of cofactors and amino acid residues in the active sites, and can be more effectively used after the positions of molecules in proteins are roughly resolved. FTIR is also useful in monitoring molecular reactions such as S-state transitions and formation of radicals in PSII, and in detecting the structural changes in cofactors and nearby proteins coupled to the reactions. Recent FTIR studies on the structures and reactions of PSII will be introduced.
