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Resonance Raman and Surface‐Enhanced Resonance Raman Spectra of LH2 Antenna Complex from Rhodobacter sphaeroides and Ectothiorhodospira sp. Excited in the Q x and Q y Transitions †
Author(s) -
Chumanov George,
Picorel Rafael,
Zarate Iñaki Ortiz,
Cotton Therese M.,
Seibert Michael
Publication year - 2000
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1562/0031-8655(2000)0710589rraser2.0.co2
Subject(s) - rhodobacter sphaeroides , bacteriochlorophyll , resonance (particle physics) , raman spectroscopy , photochemistry , chemistry , excited state , spectral line , raman scattering , pigment , photosynthetic reaction centre , purple bacteria , rhodobacter , photosynthesis , optics , atomic physics , physics , electron transfer , biochemistry , astronomy , organic chemistry , mutant , gene
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 Q x and the Q y transitions of bacteriochlorophyll a. High‐quality SERRS spectra in the Q y 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.