Surface-Enhanced Resonance Raman Scattering Spectroscopy of Plant Photosystem II Reaction Centers Excited on the Red-Edge of the Qy Band

Using surface-enhanced resonance Raman scattering (SERRS) spectroscopy techniques, we have obtained vibrational spectra from the higher plant D1-D2-cytochrome b559 photosystem II reaction center complex by exciting directly into the red-edge of the Q_y transitions of chlorophyll and pheophytin bound within the protein complex. The presence of the SERRS-active metallic Ag surface dramatically reduced the high fluorescence yield from these pigments, a serious problem that has prevented detection of resonance Raman scattering signals in the past. This report constitutes the first successful attempt to measure Raman spectra from an oxygenic photosynthetic pigment-protein complex by excitation within the Q_y transition. Consequently, SERRS spectroscopy now shows promise as an alternative vibrational spectroscopy to FT-IR for selectively examining energy transfer and redox-active chromophores involved in the dynamics of the primary processes of photosynthesis.