SURFACE-ENHANCED RESONANCE RAMAN-SCATTERING SPECTROSCOPY OF PLANT PHOTOSYSTEM-II REACTION CENTERS EXCITED ON THE RED-EDGE OF THE Q(Y) BAND

Using surface-enhanced resonance Raman scattering (SERRS) spectroscopy techniques, we have obtained vibrational spectra from the higher plan t D1-D2-cytochrome b559 photosystem II reaction center complex by exci ting 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 fluores cence yield from these pigments, a serious problem that has prevented detection of resonance Raman scattering signals in the past. This repo rt constitutes the first successful attempt to measure Raman spectra f rom an oxygenic photosynthetic pigment-protein complex by excitation w ithin the Q(y) transition. Consequently. SERRS spectroscopy now shows promise as an alternative vibrational spectroscopy to FT-IR for select ively examining energy transfer and redox-active chromophores involved in the dynamics of the primary processes of photosynthesis.