RAMAN STUDIES OF MEMBRANE ELECTRON TRANSFER COMPLEXES

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The structure and function of the native and also genetically altered (mutants) membrane-bound complexes from the photosynthetic bacterium Rhodobacter sphaeroides, which includes the reaction center, cytochrome bc1 (BC1), and cytochrome c2, as well as isolated chromophores will be investigated in this project. Time resolved resonance, surface-enhanced resonance, FT, nonlinear and UV-resonance Raman spectroscopy will be used to study these systems. Together, these techniques will provide highly sensitive and selective spectroscopic approaches that can yield complementary structural information concerning the dynamics of function. For adequate modeling of photosynthetic membranes, parallel mimetic lipid-protein systems will be constructed by monolayer techniques. Time resolved resonance Raman will provide information regarding the dynamics of structural changes in the chromophores and proteins during their functioning. UV resonance Raman spectroscopy will be developed for membrane complexes in order to establish the nature of the protein environment, the local structural changes in the protein component of these complexes and protein-chromophore interactions. FT Raman will be used to obtain nonresonance and resonance Raman spectra of the chromophores and their intermediates in the IR region. Nonlinear Raman will be attempted for obtaining additional vibrational information which is not available from normal Raman scattering. Wild-type pigment-protein complexes and complexes isolated from chemically induced, spontaneous or site-directed mutant strains will be investigated. The spectral properties will be measured in solution and at metal surfaces using surface-enhanced Raman scattering (SERS) techniques. SERS and surface-enhanced resonance Raman scattering (SERRS) spectra will be used to probe the protein topography of the membrane surface and to monitor changes that occur during charge transfer in the reaction center. Spectroscopic investigations of model systems, comprising Langmuir-Blodgett transferred monolayers of native and mutant complexes, also stabilized by lipids or synthetic polymers and absorbed on the SERS-active surfaces, will be essential for detailed topological characterization.