FTIR Studies of the Primary Electron Donor, P700

Abstract

Over the last two decades FTIR difference spectroscopy has emerged as a prominent technique to investigate the electronic structure and the bonding interactions of P700, the primary electron donor of photosystem I. In this chapter, the advances in the field during this period are reviewed and discussed in the light of the structural model of P700 derived from X-ray crystallog. The effect on the FTIR difference spectra of mutations of the axial ligands of the chlorophyll mols. in P700 as well as of amino acid residues in hydrogen bonding interaction with the carbonyl groups of P700 is analyzed. The results of both global and selective isotope labeling studies are presented. Special emphasis is given at analyzing the agreements and the discrepancies between the assignments of the various vibrational bands in the FTIR difference spectra recorded upon P700 photooxidn. that are available in literature. The reasons behind the strong disagreement between the results of FTIR spectroscopy and of magnetic resonance techniques such as ADMR and ENDOR with regard to the localization of the triplet character in 3P700 and the extent of charge vs. spin distribution in P700+ are critically discussed. [on SciFinder (R)]