Rapid-Flow Resonance Raman Spectroscopy of Bacterial Photosynthetic Reaction Centers

Rapid-flow resonance Raman vibrational spectra of bacterial photosynthetic reaction centers from the R-26 mutant of Rhodobacter sphaeroides have been obtained by using excitation wavelengths (810-910 nm) resonant with the lowest energy, photochemically active electronic absorption. The technique of...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1991-12, Vol.88 (24), p.11207-11211
Main Authors: SHREVE, A. P, CHEREPY, N. J, FRANZEN, S, BOXER, S. G, MATHIES, R. A
Format: Article
Language:English
Subjects:
Absorption spectra
Biological and medical sciences
Dimers
Emission spectra
Fluorescence
Fundamental and applied biological sciences. Psychology
Kinetics
Molecular biophysics
Photochemistry
photosynthetic apparatus
Photosynthetic Reaction Center Complex Proteins - isolation & purification
Photosynthetic Reaction Center Complex Proteins - metabolism
Radiation-biomolecule interaction
Raman scattering
Raman spectroscopy
reaction centers
Resonance
Resonant vibration
Rhodobacter sphaeroides - metabolism
Spectrum Analysis, Raman - methods
Wave excitation
Wavelengths
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Summary:Rapid-flow resonance Raman vibrational spectra of bacterial photosynthetic reaction centers from the R-26 mutant of Rhodobacter sphaeroides have been obtained by using excitation wavelengths (810-910 nm) resonant with the lowest energy, photochemically active electronic absorption. The technique of shifted excitation Raman difference spectroscopy is used to identify genuine Raman scattering bands in the presence of a large fluorescence background. The comparison of spectra obtained from untreated reaction centers and from reaction centers treated with the oxidant K3Fe(CN)6demonstrates that resonance enhancement is obtained from the special pair. Relatively strong Raman scattering is observed for special pair vibrations with frequencies of 36, 94, 127, 202, 730, and 898 cm-1; other modes are observed at 71, 337, and 685 cm-1. Qualitative Raman excitation profiles are reported for some of the strong modes, and resonance enhancement is observed to occur throughout the near-IR absorption band of the special pair. These Raman data determine which vibrations are coupled to the optical absorption in the special pair and, thus, probe the nuclear motion that occurs after electronic excitation. Implications for the interpretation of previous hole-burning experiments and for the excited-state dynamics and photochemistry of reaction centers are discussed.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.88.24.11207