Distance Measurements in Photosynthetic Reaction Centers

Distance Measurements in Photosynthetic Reaction Centers

Electron paramagnetic resonance (EPR) distance measurements have been used extensively to characterize the structure and function of photosynthetic reaction centers (RCs) in plants. CD BioSciences is committed to providing customers with distance information in photosynthetic RCs through this technology. Our dedicated technical team will develop the best experimental protocol for your research needs.


Photosynthetic RCs, also known as photochemical RCs, are energy conversion protein complexes found in algae, bacteria and higher plants. RCs play an important role in nature by efficiently harnessing light energy and driving cellular functions. In addition, RCs are important structural models for the studies of membrane-bound protein cofactor complexes and electron transfer.

However, the complexity of the systems, the difficulty of preparing diffraction-level crystals and the large size of protein complexes limit the application of multiple techniques including X-ray, electron crystallography and NMR structure determination methods in RCs. Fortunately, most of the electron transfer intermediates in the reaction centers are paramagnetic substances and are accessible by EPR techniques. Currently, EPR distance measurements have become an effective tool for studying photosynthetic RCs, providing critical information in studying the sequence, rate, and mechanism of key electron transfer events in RCs.

Schematic depicting key subunits and cofactors in PS II. The arrows indicate the sequence of electron transfer.Fig.1 Schematic depicting key subunits and cofactors in PS II. The arrows indicate the sequence of electron transfer. (Lakshmi, 2002)

Our Services

Researchers at CD BioSciences have been developing methods for studying photosynthetic RCs for many years to provide our customers with EPR distance measurements in photosystems. The services we offer include but are not limited to:

Advantages of Our Services

  • In EPR spectra, the exchange and dipole coupling between a pair of slow relaxing electron spins can manifest as linear effects. We help customers determine the interspin distance, relative orientation and degree of orbital overlap between nearest-neighbor cofactors in RCs by using typical splitting patterns observed in powder, oriented film and single crystal EPR spectral line shapes.
  • We provide spin-relaxation measurements of isolated spin pairs to directly measure the long-range interspin distances in RCs.
  • We provide distance measurements between spin labels in double-labeled proteins and between electron transfer intermediates in photosynthetic RCs through pulsed EPR techniques such as pulsed ELDOR.

Advantages of Our Services

  • Rich professional practical experience
  • Good hardware facilities and innovative techniques
  • Efficient communication and high-quality services

CD BioSciences is a technology-focused biophysical analysis service provider. Our rich and professional service experience makes us capable of providing scientific assistance to our clients in photosynthesis research including distance measurements in photosynthetic RCs. If you need any further information, please feel free to contact us. We look forward to working with you and assisting you in achieving your goals.


  1. Lakshmi, K. V.; Brudvig, G. W. Electron paramagnetic resonance distance measurements in photosystems. Distance measurements in biological systems by EPR. 2002: 513-567.
For research use only, not intended for any clinical use.
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