ИСТИНА

Cryptochromes and photolyases constitute a family of light-sensitive flavoproteins implicated in diverse sensory functions and DNA repair, respectively. In these proteins, light activation of the flavin-containing active site initiates multiple electron transfer reactions, often coupled to proton transfer, eventually leading to biological response. After crystal structures of several cryptochromes and photolyases were determined, computational studies of electron-transfer dynamics in these proteins became possible. In order to conduct such studies, we developed a complex approach that combines high-level quantum-mechanical calculations of photoactivation and electron-transfer energies and molecular dynamic simulations of protein and DNA in solution. With our approach, we obtain rates of individual electron forward- and back-transfer steps among multiple electron donors and acceptors and study how these steps are combined in order to achieve the photoactivation and DNA repair. Two specific topics addressed by our studies will be presented in this lecture - electron and proton-transfer dynamics leading to repair of the thymine-thymine (6-4) photoproduct by (6-4) photolyase and formation of long-lived radical pairs in animal and plant cryptochromes. Our simulations are particularly helpful for understanding ultrafast-spectroscopy data characterizing photoinduced electron-transfer dynamics in the wild-type and mutated cryptochromes and photolyases.