Resonance Raman spectroscopy of chlorophyll cations in photosynthetic reaction centres

A number of the pigment cofactors present in photosynthetic reaction centres can be functionally oxidised to their radical cation species. While resonance Raman spectra of the cation radical of s-carotene in photosystem II have been relatively easy to interpret, providing information on the conformation and configuration of these molecules [Pascal et al. 1999, FEBS Lett. 453, 11-14], those of chlorophyll molecules have remained somewhat elusive. We are currently measuring spectra of the oxidised primary donor of photosystem I, or P700+, with a view to defining the structure of this species at a molecular level. At the same time we hope to obtain similar spectra for oxidised chlorophyll molecules in photosystem II, and in particular chlZ+.