Protein Environments and Electron Transfer Processes Probed with High-Frequency ENDOR

  • Oleg G. Poluektov
  • Lisa M. Utschig
Part of the Advances in Photosynthesis and Respiration book series (AIPH, volume 28)


Natural photosynthetic conversion of solar energy to chemical energy is a unique phenomenon which sustains all life on Earth. The key step of photosynthetic energy conversion involves rapid, photoinduced sequential electron transfers (ET) resulting in efficient charge separation across a biological membrane. Fundamental to fully understanding these ET events is discerning the involvement of heterogeneous polypeptide environments surrounding the redox cofactor sites. High-resolution X-ray crystal structures of reaction center (RC) proteins reveal the structure of cofactors and surrounding protein environments; however, static crystallographic protein structures do not readily yield details of how native dynamic solution protein structures fine-tune ET processes and coupled reactions, such as proton transfer. Thus, novel approaches complementary to crystallography are required to experimentally correlate structural, electrostatic, and dynamic features of localized protein environments with inherent ET reactions. In this chapter we discuss one of the advanced experimental techniques being developed to tackle this problem. Using recent examples from our laboratory, we demonstrate the potential of high-frequency (HF), time-resolved (TR) electron-nuclear double resonance (ENDOR) spectroscopy to reveal unique information about structure/function relationships in photosynthetic ET. First, we discuss light-induced protein conformational states of P+Q B trapped in purple photosynthetic bacterial RCs at low temperature and matrix ENDOR techniques for examining the local protein environment surrounding Q B for these states. Second, we describe the HF TR ENDOR study of the spin-correlated radical pair P+Q A . These experiments permit us to directly probe light-induced reorganization of the protein in response to the rapid formation of the charge-separated state. General principles obtained from the novel application of these methodological approaches to native biological systems will help in the development of biomimetic solar energy conversion assemblies.


Electron Paramagnetic Resonance Electron Paramagnetic Resonance Spectrum Electron Paramagnetic Resonance Signal Rhodobacter Sphaeroides Photosynthetic Reaction Center 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



phylloquinone acceptor




delay after flash


electron-nuclear double resonance


electron paramagnetic resonance


electron spin echo


electron transfer




hyperfine interactions




primary donor


primary chlorophyll electron donor






reaction center




spin-correlated radical pair






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© Springer Science + Business Media B.V 2009

Authors and Affiliations

  1. 1.Chemistry DivisionArgonne National LaboratoryArgonneUSA

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