Characterization of Photosynthetic Reaction Centers by Surface-Enhanced Resonance Raman Scattering

Surface-enhanced Resonance Raman scattering (SERRS) spectra were obtained for the reaction center complexes of the photosynthetic bacterium Rhodobacter sphaeroides (RC) and from photosystem II (PSII) of spinach, adsorbed on Ag and Au surfaces. These preliminary results demonstrate the considerable potential of this technique for selectively exciting resonance Raman scattering from reaction center components within their distinct absorption bands. Because of the high sensitivity afforded by SERRS, spectra could be measured from a single monolayer of reaction centers adsorbed on a metal surface. The surface-sensitivity provides new information indicating the topology of the PSII reaction center 47 kD light-harvesting protein complex. The activity of the PS II reaction center complex adsorbed on metal surfaces was monitored by photochemical reduction of cyt b-559. Measurement of fluorescence emission was shown to be a new and sensitive method for monitoring the structural and functional integrity of the PS II reaction center complex on the metal surface.