Spin dynamics and EPR spectra of charge separated states in photosystem 1 reaction center

A novel strategy is discussed using site-directed spin labeling to study the electron transfer process in photosynthetic reaction centers. An algorithm is presented for numerical simulations of the time-resolved EPR spectra of radical pair states in the presence of an observer spin label. The transient EPR spectra for the radical pair in Photosystem I were simulated for various distances and positions of the observer spin label with respect to the acceptor quinone molecule. Furthermore, the shape and intensity of the EPR spectrum of the spin label is changed remarkably due to the coupling with the radical pair spins.