Resonance Raman and Surface-Enhanced Resonance Raman Spectra of LH2 Antenna Complex from Rhodobacter Sphaeroides and Ectothiorhodospira sp. Excited in the Qx and Qy Transitions

George Chumanov, Rafael Picorel, Iñaki Ortiz De Zarate, Therese M. Cotton, Michael Seibert

Research output: Contribution to journalArticlepeer-review

10 Scopus Citations

Abstract

Well-resolved vibrational spectra of LH2 complex isolated from two photosynthetic bacteria, Rhodobacter sphaeroides and Ectothiorhodospira sp., were obtained using surface-enhanced resonance Raman scattering (SERRS) exciting into the Qx and the Qy transitions of bacteriochlorophyll a. High-quality SERRS spectra in the Qy region were accessible because the strong fluorescence background was quenched near the roughened Ag surface. A comparison of the spectra obtained with 590 nm and 752 nm excitation in the mid- and low-frequency regions revealed spectral differences between the two LH2 complexes as well as between the LH2 complexes and isolated bacteriochlorophyll a. Because peripheral modes of pigments contribute mainly to the low-frequency spectral region, frequencies and intensities of many vibrational bands in this region are affected by interactions with the protein. The results demonstrate that the microenvironment surrounding the pigments within the two LH2 complexes is somewhat different, despite the fact that the complexes exhibit similar electronic absorption spectra. These differences are most probably due to specific pigment-pigment and pigment-protein interactions within the LH2 complexes, and the approach might be useful for addressing subtle static and dynamic structural variances between pigment-protein complexes from different sources or in complexes altered chemically or genetically.

Original languageAmerican English
Pages (from-to)589-595
Number of pages7
JournalPhotochemistry and Photobiology
Volume71
Issue number5
DOIs
StatePublished - 2000

NREL Publication Number

  • NREL/JA-590-25991

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