Time-resolved EPR spectroscopy of photosynthetic reaction centers: from theory to experiment

• Published in: Applied magnetic resonance 2007-03, Vol.31 (1-2), p.105-122
• Main Authors: Kandrashkin, Y. E., van der Est, A.
• Format: Article
• Language: English
• Subjects: Electron paramagnetic resonance; Electron spin; Electron transfer; Photosynthesis; Polarization (spin alignment); Qualitative analysis; Spectra
• ISSN: 0937-9347; 1613-7507
• DOI: 10.1007/BF03166250

A theoretical description of the electron spin polarization in sequential radical pairs generated by light-induced electron transfer is reviewed and several examples of its application to experimental time-resolved electron paramagnetic resonance from photosynthetic reaction centers are given. It is shown that most of the features of the observed spectra can be understood in terms of basic properties of the radical paris. The most crucial aspect used in the analysis is that the polarization of the observed radical pairs predominantly inherits the singlet character of the initial excited state of the primary donor. The motion of the spins also generates a small amount of additional polarization during the course of the sequential electron transfer. The theory provides a simple set of rules for qualitative interpretation of experimental data as well as a mathematical model for quantitative simulations of spectra. The comparison of simulated and experimental spectra demonstrates excellent agreement.