RESONANCE-ENHANCED CARS SPECTROSCOPY OF BILIPROTEINS - INFLUENCE OF AGGREGATION AND LINKER PROTEINS ON CHROMOPHORE STRUCTURE IN ALLOPHYCOCYANIN (MASTIGOCLADUS-LAMINOSUS)

Resonance-enhanced coherent anti-Stokes Raman spectra (CARS) are repor ted for monomers and for trimers with and without linker proteins of a llophycocyanin isolated from Mastigocladus laminosus. The CARS spectru m of the monomer is independent of the presence of Linker proteins and is very similar to that of phycocyanin monomers indicating that the e quivalent chromophores exhibit like structures in both biliproteins. L arge differences are, however, observed between the spectra of phycocy anin trimers and those of allophycocyanin trimers with or without link er proteins (L(C)(8,9)). The observed differences between monomer and trimer spectra are consistent with a change of the alpha-chromophore-p rotein arrangement upon aggregation without linker. If linker proteins are present in the trimer, then additional geometry changes of the be ta-chromophores are induced; these could relate to a transition from t he 15Z-anti to 15Z-syn conformation.